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Tamilnadu Samacheer Kalvi 11th Chemistry Notes Chapter 7 Thermodynamics Notes

Thermodynamics – It means flow of heat. It is a branch of science which deals the relation between energy, heat, work and accompanying changes in the nature and behaviour of various substances around us.

Macroscopic properties – Heat and work.

First law of Thermodynamics – It states that “The total energy of an isolated system remains constant though it may change from one form to another”.

ΔU = q + w
ΔU – Change in the internal energy
q – Amount of heat supplied to the system
w – Amount of work done on the system

System – It is defined as any portion of matter under thermodynamic consideration, which is separated from the rest of the universe by real or imaginary boundaries.

Homogeneous system – If the physical states of all its matter are uniform, it is called homogeneous system.

Heterogeneous system – If the physical states of all its matter are not uniform, it is called heterogeneous system.

Surroundings – Everything in the universe that is not the part of system is called surroundings.

Boundary – Anything which separates the system from its surrounding is called boundary.

Isolated system – A system which can exchange neither matter nor energy with its surroundings is called an isolated system, e.g., Hot water contained in a thermos flask.

Closed system – A system which can exchange only energy but not matter with its surroundings is called a closed system, e.g., Hot water contained in a closed beaker.

Open system – A system which can exchange both matter and energy with its surroundings is called an open system, e.g., Hot water contained in an open beaker.

Intensive properties – The properties that are independent of the mass or size of the system is called as intensive property, e.g., Refractive index, surface tension, density, temperature, boiling point and freezing point etc.

Extensive properties – The properties that are depended on the mass or size Of the system is called as extensive property, e.g., Volume, number of moles, mass and internal energy etc.

Thermodynamic process – The method of operation which can bring about the change in the system is called thermodynamic process, e.g., Heating, cooling and fusion.

Reversible process – The process in which the system and surroundings can be restored to the initial state from the final state without producing any changes in the thermodynamic properties of the universe is called a reversible process.

Irreversible process – The process in which the system and surroundings cannot be restored to the initial state from the final state is called an irreversible process.

Adiabatic process – It is defined as one in which there is no exchange of heat (q) between the system and surrounding during process, [q = 0]
304 Chemistry-11 :

Isothermal process – It is defined as one in which the temperature of the system remains constant, during the change from its initial to final state. [dT = 0]

Isobaric process – It is defined as one in which the pressure of the system remains constant during its change from the initial to final state. [dP = 0]

Isochoric process – It is defined as one in which the volume of system remains constant during its change from initial to final state. [dV= 0]

Cyclic process – When a system returns to its original state after completing a series of changes the process is known as a cyclic process. For a cyclic process dU = 0, dH = 0, dP = 0, dV= 0 and dT= 0.

State functions – The properties of P, V, T and ‘n’ that are used to describe the state of a system are called as state functions.

Path functions – A path function is a thermodynamic property of the system whose value depends on the path by which the system goes from its initial to final states, e.g., Work and heat.

Internal energy – Internal energy of a system is equal to the energy possessed by all its constituents namely atoms, ions and molecules.
U = Internal energy = U_t + U_v + U_r + U_b + U_e + U_i.

ΔU – Change in internal energy = U_f– U_i.

Heat (q) – It is regarded as an energy in transit across the boundary separating a system from its surrounding. It is a path function.

Units of heat – SI unit of heat is joule (J).The other unit is calories (cal).

Calories (cal) – It is defined as the quantity of heat required to raise the temperature of 1 gram of water by 1 °C in the vicinity of 15°C.

Work (w) – It is defined as the force (F) multiplied by the displacement (x). [- w = F. x ]

Unit of work – SI unit of work is joule (J) or kilojoule (kJ).

Joule – It is defined as the work done by a force of one Newton through a displacement of one meter (J = Nm).

Gravitational work – When an object is raised to a certain height against the gravitational field, gravitational work is done on the object, [w = m.g.h]

Electrical work – When a charged body moves from one potential region to another, electrical work is done, [w = QV]

Mechanical work – It is defined as force multiplied by the displacement through which the force acts, [w = F. x]

Pressure – Volume work – The work done in expansion or compression of a gas. PV work (or) expansion work.

Work involved in expansion and compression process – [w = -PΔV]

Expansion – During expansion, work is done by the system. Since V_f > V_i., the sign obtained for work will be negative.

Compression – During compression, work is done on the system. Since V_f < V_i the sign obtained for work will be positive.

For Reveresible process w_rev = 2.303 nRT log \(\left(\frac{\mathrm{V}_{f}}{\mathrm{~V}_{i}}\right)\)

Zeroth law of thermodynamics – This law states that ‘If two systems are separately in thermal equilibrium with a third one, then they tend to be in thermal equilibrium with themselves’.

First law of thermodynamics – “Energy can neither be created nor destroyed, but may be converted from one form to another”.
(or)
The total energy of a system and surroundings remains constant (or conserved).
ΔU = q + w

Mathematical statement of first law –

Enthalpy (H) – It is defined as the sum of the internal energy (U) of a system and the product of pressure and volume of the system.
H = U + PV
ΔH = ΔU + PΔV

Relation between enthalpy ‘H’ and internal energy ‘U’ –
ΔH — ΔU + Δn_(g)RT

Standard heat of formation – It is defined as “the change in enthalpy that takes place when one mole of a compound is formed from its elements, present in their standard states (298K and 1 bar pressure).

Thermochemical equations – It is a balanced stoichiometric chemical equation that includes the enthalpy change (ΔH).

Standard enthalpy of reaction (ΔH⁰_r) – It is the enthalpy change for a reaction when all the reactants and products are present in their standard states.
\(\Delta \mathrm{H}_{r}^{0}=\Sigma \Delta \mathrm{H}_{r}^{0} \text { (products) }-\Sigma \Delta \mathrm{H}_{r}^{\theta} \text { (reactants) }\)

Heat of combustion (ΔH_c) – It is defined as the change in enthalpy of a system when one mole of the substance is completely burnt in excess of air or oxygen.

Specific heat capacity (C) – It is defined as the heat absorbed by one kilogram of a substance in raising its temperature by one Kelvin at a specified temperature.
\(\mathrm{C}=\left[\frac{q}{m\left(\mathrm{~T}_{2}-\mathrm{T}_{1}\right)}\right]\)

Molar heat capacity – It is defined as the amount of heat absorbed by one mole of the substance to raise its temperature by 1 Kelvin.
c_m = q/ΔT

Unit of heat capacity – JK^-1 mol^-1

C_v : (Molar heat capacity at constant volume) – It is defined as the rate of change of internal energy with respect to temperature at constant volume.
\(C_{V}=\left(\frac{d U}{d T}\right)_{V}\)

Cp: (Molar heat capacity at constant pressure) – It is defined as the rate of change of enthalpy with respect to temperature at constant pressure.
\(C_{P}=\left(\frac{d H}{d T}\right)_{P}\)

Relation between Cp and Cv for an ideal gas –
C_p – C_v = nR

Calorimetry – It is the science associated with determining the changes in energy of a system by measuring the heat exchanged with the surroundings. ,

Exothermic reaction – The reaction in which heat is evolved and system loses heat to the surroundings. [ΔH_r = -ve]

Endothermic reaction – The reaction in which heat is absorbed and system gains heat from the surroundings. [ΔH_r= +ve] .

Calorific value – It is defined as the amount of heaf produced in calories (or joules) when one gram of a substance is completely burnt. The SI unit is J kg^-1.

Heat of solution – It is defined as the change in enthalpy of the system when one mole of a substance is dissolved in a specified quantity of a solvent at a given temperature.

Heat of neutralisation – It is defined as the change in enthalpy of the system when one gram equivalent of an acid is completely neutralised by one gram equivalent of a base in dilute solution.

Molar heat of fusion – It is defined as the change in enthalpy when one mole of a solid substance is converted into the liquid state at its melting point.

Molar heat of vapourisation – It is defined as the change in enthalpy when one mole of a liquid is converted into vapour or gaseous state at its boiling point.

Molar heat of sublimation – It is defined as the change in enthalpy when one mole of a solid is directly converted into the gaseous state at its sublimation temperature.

Heat of transition – It is defined as the change in enthalpy when one mole of an element changes from one allotropic form to another.

Hess’s law of constant heat summation – It states that “the enthalpy change of a reaction either at constant volume or constant pressure is the same whether it takes place in a single step or multiple steps provided the initial and final states are same”.

Lattice energy – It is defined as the amount of energy required to completely remove the constituent ions from its crystal lattice to an infinite distance.

Born Haber’s cycle – It applies Hess’s law to calculate lattice enthalpy.

Second law of thermodynamics –
(i) Entropy statement: “Whenever a spontaneous process takes place, it is accompanied by an increase in the total entropy of the Universe”.
ΔS_Universe > ΔS_system + ΔS_surroundings

(ii) Kelvin-Planck statement – It is impossible to take heat from a hotter reservoir and convert it completely into work by a cyclic process without transferring a part of heat to a cooler reservoir.

% Efficiency – \(\left[\frac{\mathrm{T}_{1}-\mathrm{T}_{2}}{\mathrm{~T}_{1}}\right] \times 100\)

Clausius statement – It states that heat flows spontaneously from hot objects to cold objects and to get it flow in the opposite direction, we have to expend some work.

Spontaneous process – A reaction that does occur under the given set of conditions without any external driving force is called a spontaneous reaction.

Non-spontaneous process – A reaction that does not occur under given set of conditions without any external driving force is called a non-spontaneous reaction.

Entropy (S) – It is defined as “for a reversible change taking place at a constant temperature (T), the change in entropy (AS) of the system is equal to heat energy absorbed or evolved (q) by the system divided by the constant temperature (T)”. \(\Delta S_{\text {sys }}=\frac{q_{\text {rev }}}{T}\)

Unit of entropy – JK^-1(SI unit).

Standard entropy of formation – It is defined as the entropy of formation of 1 mole of a compound from the elements under standard conditions. It is denoted as \(\Delta \mathrm{S}_{f}^{0}\)

Standard entropy change AS⁰ –
\(\Delta \mathrm{S}_{r}^{0}=\Sigma \mathrm{S}_{\text {products }}^{0}-\Sigma \mathrm{S}_{\text {reactants }}^{0}\)

Entropy of fusion – When one mole of the solid melts at its melting point reversibly, the heat absorbed is called molar heat of fusion.
\(\Delta \mathrm{S}_{f}=\frac{\Delta \mathrm{H}_{f}}{\mathrm{~T}_{f}}\)
ΔH_f = Molar heat of fusion
T_f= Melting point

Entropy of vapourisation – When one mole of liquid is boiled at its boiling point reversibly, the heat absorbed is called molar heat of vapourisation.
\(\Delta \mathrm{S}_{v}=\frac{\Delta \mathrm{H}_{v}}{\mathrm{~T}_{b}}\)

ΔH_v = Molar heat of vapourisation
T_b = Boiling point

Entropy of transition – The heat change, when one mole of a solid changes reversibly from one allotropic form to another at its transition temperature.
\(\Delta \mathrm{S}_{t}=\frac{\Delta \mathrm{H}_{t}}{\mathrm{~T}_{t}}\)
ΔH_t = Molar heat of transition .
T_t = Transition temperature

Gibbs free energy – It is the available energy to do the work. It is defined as the part of total energy of a system that can be converted (or) available for conversion into work.
G = H – TS
ΔG = ΔH – TΔS
ΔG = -w- PΔV

Reaction quotient (Q) – It is defined as the ratio of concentration of the products to the concentrations of the reactants under non equilibrium conditions.

ΔG° = Standard free energy change of the reaction.
ΔG = ΔG° + RT In Q
ΔG⁰ = – RT In K_eq
ΔG⁰ = – 2.303 RT log K_eq
ΔG⁰ = ΔH⁰ – TΔS⁰ = – RT In K_eq

Third law of thermodynamics – It states that the entropy of pure crystalline substance at absolute zero is zero (or) it is impossible to lower the temperature of an object to absolute zero in a finite number of steps, \(\lim _{T \rightarrow 0} S=0\)

Samacheer Kalvi 11th Chemistry Notes

Tamilnadu Samacheer Kalvi 11th Chemistry Notes Chapter 6 Gaseous State Notes

Gases at STP – H₂, N₂, O₂, F₂, Cl₂, O₃, He, Ne, Ar, Kr, Xe and Rn (Only 11 elements).

The Earth – The Earth is surrounded by a atmosphere of air whose composition is 78% Nitrogen, 21% Oxygen and 1% other gases.

Oxygen – It is highly essential for our survival.

Hydrogen cyanide (HCN) – Deadly poison

Carbon monoxide (CO) – Highly toxic

NO₂ and SO₂ – less toxic

Chemically inert gases – He, Ne, Ar, Kr, Xe and Rn.

Gas – A substance is normally in a gaseous state at ordinary temperature and pressure.

Vapour – The gaseous form of any substance that is a liquid or solid at NTP. Gaseous State

Pressure – It is defined as the force exerted by a gas on unit area of the wall.
Pressure = \(\frac{\text { Force }}{\text { area }}=\frac{\mathrm{F}}{\mathrm{a}}\)

Unit of pressure (Pascal) – 1 Pascal = 1 Nm^-2,where 1 N = 1 Kg m s^-2. Other units of pressure are Bar, atmosphere, Torr, mm of Hg.

Atmospheric pressure – The force exerted on a unit area of earth by the column of air above it is called atmospheric pressure.

1 atm – 760 mm Hg

Boyle’s law – At a given temperature, the volume occupied by a fixed mass of a gas is inversely proportional to its pressure.
V ∝ 1/p at constant T (or)
PV = K₁ at constant T (or)
P₁V₁ = P₂V₂ = K₁

Charles’ law – For a fixed mass of a gas at constant pressure, the volume is directly proportional to temperature (K).
V ∝ T and constant P and n : V/T = Constant

Absolute zero : -273.15°C.

Gay-Lussac’s law – At constant volume, the pressure of a fixed mass of gas is directly proportional to temperature. P ∝ T at constant V ; P/T = Constant.

Avogadro’s hypothesis – Equal volumes of all gases under the same condition of temperature
and pressure contain equal number of molecules.
V ∝ n (or) \(\frac{\mathrm{V}_{1}}{n_{1}}=\frac{\mathrm{V}_{2}}{n_{2}}=\text { Constant }\)

Ideal gas equation – PV = nRT where R is universal gas constant.

Values of R –
R = 0.082057 dm³ atm mol^-1 K^-1
R = 8.314 × Pa m³ K^-1mol^-1
R = 8.314 × 10^-2 bar dm³ K^-1mol^-1
R = 8.314 JK^-1mol^-1

Dalton’s law of partial pressures – It states that the total pressure of a mixture of gases is the sum of partial pressures of the gases present.
P_total = p₁+P₂ + P₃ ……………..

Graham’s law of Diffusion – The rate of effusion or diffusion is inversely proportional to the square of molecular mass of a gas through an orifice.
\(\frac{r_{A}}{r_{B}}=\sqrt{\frac{M_{B}}{M_{A}}}\)

Ideal gases – Gases that obey ideal gas equation PV = nRT are ideal gases.

Real gases – Gases that do not obey the ideal gas equation PV = nRT are real gases. For them either PV > nRT or PV < nRT

Van der Waals equation of state –
\(\left(\mathrm{P}+\frac{\mathrm{an}^{2}}{\mathrm{~V}^{2}}\right)(\mathrm{V}-\mathrm{nb})=\mathrm{nRT}\)
Where a and b are Van der Waals constant.

Critical constants –
Critical Volume V_c = 3b
Critical Pressure P_c = \(\frac{a}{27 b^{2}}\)
Critical Temperature T_c = \(\frac{8 \mathrm{a}}{27 \mathrm{Rb}}\)

Critical temperature of CO₂ – 303.98 K

Critical Temperature – T_c is defined as the temperature below which a gas can be liquefied by the application of pressure.

Critical Pressure – P_c is the pressure required to liquefy a gas at its critical temperature.

Critical Volume – V_c is the volume occupied by one mole of a gas at its critical temperature aftd critical pressure.

Joule Thomson effect – The phenomenon of producing lowering of temperature when a gas is made to expand adiabatically from a region of high pressure into a region of low pressure.

Inversion temperature ( T_i) – The temperature below which a gas obey Joule Thomson effect is called inversion temperature. \(\mathrm{T}_{\mathrm{i}}=\frac{2 \mathrm{a}}{\mathrm{Rb}}\)

Samacheer Kalvi 11th Chemistry Notes

Tamilnadu Samacheer Kalvi 11th Chemistry Notes Chapter 5 Alkali and Alkaline Earth Metals Notes

s-block elements – Group 1 and 2 elements are those in which the last electron enters the outermost s-orbital.

Group 1 elements – Alkali metals Li, Na, K, Rb, Cs and Fr with electronic configuration as noble gas [ns¹].

Occurrence of Alkali metals

Half-life of francium – 21 minutes.

Oxidation state of alkali metals – +1.

Atomic radii and ionic radii of alkali metals – On moving down the group increases and across the period decreases.

Periodic trends in alkali group – Reactivity, atomic radius, formation of electropositive ion and density increases down the group. Melting point and boiling point decreases down the group.

Distinctive behaviour of lithium – Extremely small size, greater polarizing power of ion, least electropositive character and non-availability of d-orbitals.

Chemical properties – Alkali metals are highly reactive and reacts with oxygen, hydrogen, halogen and liquid ammonia.

Uses of alkali metals – Oxidizing agents (oxide of alkali metals), strong bases (hydroxides of alkali metals), sodium and potassium ions perform important biological functions such as ion balance and nerve impulse conduction.

Fruits rich in potassium – Avocadoes, potatoes and bananas.

Group 2 elements – Alkaline earth elements with general electronic configuration as [noble gases] ns2. They are Be, Mg, Ca, Sr, Ba and Ra.

Alkaline earth metals – Except Be, all other oxides and hydroxides are alkaline in nature.

Occurrence of alkaline earth metals –

Pyrotechnics – Alkaline earth metals are used to produce colours in firework shows.

Oxidation state of alkaline earth metals – +2.

Trends in periodic properties –

• Atomic and ionic radii increases down the group.
• Ionization enthalpy and hydration enthalpy decreases down the group.

Anomalous behavior of beryllium – (i) Small size (ii) high polarizing power (iii) high electronegativity (iv) absence of vacant d-orbital (v) high ionization enthalpy.

Chemical properties – Alkali metals react with H., and halogens.

Uses of beryllium –

• Used as radiation windows for X-ray tube and X-ray detectors.
• As sample holder in X-ray emission studies.
• Used to build the beam pipe in accelerators.
• Used in detectors.

Uses of magnesium –

• For the removal of sulfur from iron and steel.
• For the refining of titanium.
• Used as photoengrave plates in printing industry.
• Magnesium alloys are used in airplanes and missile construction.
• Mg ribbon is used in Grignard reagent synthesis.
• As desiccant.
• As sacrificial anode in controlling galvanic corrosion.
• As a reducing agent.
• Mg + A1 alloy used in fabrication and welding.

Uses of calcium –

• Used as a reducing agent in the metallurgy of uranium, zirconium and thorium.
• As a deoxidizer, desulfurizer or decarbonizer for ferrous and non-ferrous alloys.
• As a getter in vacuum tubes.
• In making of cements and mortars.
• In dehydrating oils.
• In fertilizers, concrete and making Plaster of Paris.

Uses of strontium –

• ⁹⁰Sr is used in cancer therapy.
• ⁸⁷Sr / ⁸⁶Sr ratio is used in marine investigations as well as in teeth, tracking animal migrations or in criminal forensics.
• Used in dating of rocks.
• Used as a radioactive tracer.

Uses of barium –

• Used in metallurgy, pyrotechnics, petroleum mining and radiology.
• Deoxidizer in copper refining.
• Ba + Ni alloy is used in electron tubes and in spark plug electrodes.
• As a scavenger to remove oxygen and other gases in television and electronic tubes.
• ¹³³Ba is used as a source in the calibration of gamma ray detector.

Uses of radium – Used in self-luminous paints for watches, nuclear panels, aircraft switches, clocks and instrument dials.

Chemical properties of alkaline earth metals –

• They form monoxides and peroxide with oxygen.
• The oxides of alkaline earth metals react with water to give hydroxides.
• They form halides when react with halogens.
• Alkaline earth metals form salts of oxo-acids such as carbonates, sulphates and nitrates.

Important compounds of calcium –

Quick lime – CaO

Slaking of lime – The process of addition of limited amount of water breaks the lump of lime is called slaking of lime.

Uses of quick lime –

• To manufacture cement, mortar and glass.
• To manufacture sodium carbonate and slaked lime.
• In the purification of sugar.
• As drying agent.

Slaked lime – Ca(OH)₂

Bleaching powder – Ca(OCl)₂

Uses of slaked lime –

• In the preparation of mortar, a building material.
• In white wash.
• In glass making and in tanning industry.
• For the preparation of bleaching powder and in purification of sugar.

Gypsum – CaSO₄.2H₂O

Desert Rose – Gypsum crystals are found to occur in a form that resembles the petals of a flower and this occur in desert terrains.

Alabaster – A variety of gypsum and valued as an ornamental stone.

Plaster of Paris – CaSO₄.1/2 H₂O

Uses of gypsum –

• It has been used by the sculptors.
• To prepare Plaster of Paris.
• Used in making dry walls or plaster boards.
• It is used in making surgical and orthopedic casts, casting molds and surgical splints.
• It is used in agriculture as a soil additive, conditioner and fertilizer.
• It is used in toothpaste, shampoo and hair products.

Calcium sulfate – Acts as a coagulator in making tofu. It is used in baking, as a dough conditioner. It is used to treat upset stomach and eczema.

Gypsum – It is used as a hardening retarder to control the speed at which concrete sets.

Satin spar – It is a variety of gypsum, used as an ornamental stone, while alabaster is used for sculpting.

Gypsum – It is used to give colour to cosmetics and drugs. It can be found in canned vegetables, flour, ice cream, blue cheese and white bread. It is mainly used in wine making.

Uses of Plaster of Paris –

• It is used in building industry as well as plasters.
• It is used for immobilizing the affected part of organ, where there is a bone fracture or sprain.
• It is also used in dentistry, making casts of statues and busts.

Biological importance of magnesium and calcium –

• An adult body contains about 25 g of Mg and 1200 g of Ca. The daily requirement in the human body has been estimated to be 200 – 300 mg.
• All enzymes transfer requires magnesium as the co-factor. The main pigment of chlorophyll is magnesium.
• 99% of body calcium is present in bones and teeth. It also play important roles in neuromuscular function, intemeuronal transmission, cell membrane integrity and blood coagulation.
• The calcium concentration is maintained by two hormones – calcitonin and parathyroid hormones.

Samacheer Kalvi 11th Chemistry Notes

Tamilnadu Samacheer Kalvi 11th Chemistry Notes Chapter 4 Hydrogen Notes

Occurrence of Hydrogen – the sun and stars are composed of 85—95% Hydrogen. It is present in the form of water, organic compounds and in all lIving matter.

Occurrence of Hydrogen – the sun and stars are composed of 85—95% Hydrogen. It is present in the form of water, organic compounds and in all lIving matter.

H → f electrically neutral
H⁺ → Proton
H^– → Hydride
H₂ → diatomic gaseous molecule.

Ortho hydrogen – The hydrogen molecule in which the nuclear spins of the two hydrogen atoms are in the same side. Magnetic moment of it is twice.

Para hydrogen – The hydrogen molecule in which the nuclear spins of the two hydrogen atoms are in the opposite side. Magnetic moment of it is zero.

Isotopes of hydrogen – Protium \({ }_{1}^{1} \mathrm{H}\), Deuterium ,\({ }_{1}^{2} \mathrm{H}\) and Tritium \({ }_{1}^{3} \mathrm{H}\).

Half life period of Tritium – 12.33 years.

Isotopic effect – In a chemical reaction, when one of the atoms in the reactants is replaced by one of its isotopes.

Uses of Deuterium – It is used to study the movement of ground water and the hydrogen atom transfer mechanism in chemical reactions.

Uses of Tritium – It is used as a tracer element and it find applications such as emergency exit signs, illumination of wrist watches.

Preparation of Tritium – It occurs naturally as a result of nuclear reactions induced by cosmic rays in the upper atmosphere.

Preparation of Hydrogen

• Electrolysis of water.
• Action of dilute acids with metals like zinc, iron, tin.
• Steam reforming of hydrocarbons.
• Reaction of steam with red hot coke.
• Reaction of carbon monoxide with water.
• Cracking of long chain hydrocarbons.

Properties of hydrogen – It is a colourless, odourless, tasteless, lightest and inflammable gas.

Uses of hydrogen

1. In the manufacture of Ammonia and Nitric acid.
2. In the synthesis of methanol.
3. As hydrogenating agent.
4. As reducing agent in metallurgy.
5. Calcium hydride is used as desiccant (drying agent).
6. NaBH₄, LiAlH₄ used as reducing agent in organic chemistry.
7. Atomic hydrogen and oxyhydrogen torches for cutting and welding.
8. Liquid hydrogen is used as rocket fuel.
9. H₂ is used in fuel cells for generating electricity.

Water – H₂O. It is the universal solvent. It occurs in the form of rivers and oceans (97.33%).

Ortho H₂O and Para H₂O – At the temperature conditions of the earth (300K), the OPR of H2O is 3. It is known that the OPR of water in interstellar clouds and comets has more para- H₂O (OPR = 2.5) than on Earth.

Physical properties – Water is a colourless and volatile liquid. Hydrogen bonding responsible for high melting and boiling points of water.

Chemical properties – Water reacts with metals, non-metals and compounds.

Hard water – Water containing high amounts of bicarbonate, chloride and sulphate of magnesium and calcium is called hard water.

Soft water – Water containing soluble salts of calcium and magnesium is called soft water.

Soap – Sodium or Potassium salts of long chain fatty acids.

Temporary hardness – It is due to the presence of soluble bicarbonates of magnesium and calcium. It is removed by heating or by treating with lime.

Permanent hardness – It is due to the presence of soluble salts of magnesium and calcium in the form of chlorides and sulphates in water. It can be removed by washing soda or by ion exchange.

Ion exchange – Hardness of water can be removed by passing through an ion exchange bed like zeolites or polymer (resin) containing column.

Zeolites – Hydrated sodium alumino-silicates NaO.Al₂O₃.xSiO₂.yH₂O (x = 2-10, y = 2-6).

Premutit (or) zeolite process – The softening of water process by using complex structure represented as Na₂ – Z with sodium as exchangeable cations.

Methods used to soften hard water – Chelating method and reverse osmosis.

Chelating method – EDTA is used in this.

Reverse osmosis – High pressure to force water through a semipermeable membrane.

Heavy water – D₂O. It is present as one part in 5000 parts of ordinary water.

Preparation of D₂O – It is prepared by continuous electrolysis of ordinary water. It undergoes exchange reactions.

Uses of D₂O – D₂O is used in isotopic effect, used as moderator in nuclear reactors, used to prepare deuterium compounds.

Hydrogen peroxide (H₂O₂) – It is a pale blue (almost colourless) liquid. It is prepared by the action of dilute acid with metal peroxide.

Uses of H₂O₂ – Oxidising agent, mild antiseptic, as a bleaching agent in textile, paper and hair-care industry and used as reducing agent.

Structure of H₂O₂ –

Hydrides – A binary hydride is a compound formed by hydrogen with other electropositive elements, e.g. LiH, MgH₂.

Ternary hydrides – Compounds in which molecule is constituted by hydrogen and two types of elements, e.g. LiBH₄, LiAlH₄.

Types of hydrides –

Hydrogen sponge – Metal hydride as (PdH) Palladium hydride. It is formed by a chemical reaction but it behaves like a physical storage method, i.e., it is absorbed and released like a water sponge.

Hydrogen bonding – When a hydrogen atom is covalently bonded to a highly electronegative atom [ N (or) D (or) F], the bond is polarised in such a way that the hydrogen atom is able to form a weak bond between the hydrogen atom and the electronegative atom of a second molecule. This is called a hydrogen bond and denoted as dotted lines (…………….).

Types of hydrogen bonding – Intra molecular hydrogen bonding and inter molecular hydrogen bonding.

Intra molecular hydrogen bonding – These bonds are those which occur within one single molecule. e.g.T ortho-nitrophenol and salicylaldehyde.

Inter molecular hydrogen bonding – These bonds are formed between two separate molecules, e.g., Ammonia, water, hydrogen fluoride, acetic acid.

Gas hydrates – They are a kind of inclusion compounds, where gas molecules are trapped in a crystal lattice having voids of right size, with being chemically bonded, e.g., H₃O⁺ in gas phase similar to methane hydrate.

Clatharate hydrate – Gas hydrates in which guest molecules are not bonded chemically but retained by the structure of host is called Clatharate hydrates, e.g., Methane hydrate CH₄.20H₂O.

Crystalline hydrates – In this type, hydrogen bonding is present. Water molecules serve to fill in the interstices and bind together structure, e.g., CuSO₄.5H₂O, Na₂CO₃.10H₂O, FeSO₄.7H₂O.

The atomic bomb – The hydrogen bomb uses both nuclear fission and fusion is called atom bomb or Thermonuclear bombs.

The future fuel – Hydrogen is considered as a potential fuel as it is a clean burning fuel. This fuel is free from pollutants.

Samacheer Kalvi 11th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 12 Carbonyl Compounds Notes

Carbonyl compounds: An organic compounds, which contains is called carbonyl compounds. They plays an important role in the metabolic process. Carbonyl compounds are important constituents of fabrics, plastics and drugs.

Ozonolysis: Alkenes or Alkynes reacts with ozone to form ozonide which on subsequent cleavage with zinc and water gives corresponding aldehydes or ketones. This process is known as ozonolysis.

Hydration of alkynes: The hydration of alkynes in the presence of 40% dilute sulphuric acid and 1% H₂SO₄ to give the corresponding aldehydes or ketones.

Rosenmund reduction: Aldehydes can be prepared by the hydrogenation of acid chloride, in the presence of palladium supported by barium sulphate. This reaction is called Rosenmund reduction.

Stephen’s reaction: When alkylcyanides are reduced using SnCl₂ / HCl, imines are formed, which on hydrolysis gives corresponding aldehyde. This reaction is called Stephen’s reaction.

Selective reduction of cyanides: Diisobutyl aluminium hydride (DIBAL -H) selectively reduces the alkyl cyanide to form imines which on hydrolysis gives aldehydes.

Etard reaction: When chromylchloride is used as an oxidising agent, toluene gives benzaldehyde. This reaction is called Etard reaction.

Gattermann – Koch reaction: In this reaction, carbon monoxide and HC1 generate formyl cation intermediate, which attacks the aromatic ring to form corresponding aldehydes.

Urotropine: Formaldehyde reacts with ammonia to form hexa methylene tetramine, which is also known as Urotropine.

Carbonyl compounds: An organic compounds, which contains c is called carbonyl compounds. They plays an important role in the metabolic process. Carbonyl compounds are important constituents of fabrics, plastics and drugs.

Ozonolysis: Alkenes or Alkynes reacts with ozone to form ozonide which on subsequent cleavage with zinc and water gives corresponding aldehydes or ketones. This process is known as ozonolysis.

Hydration of alkynes: The hydration of alkynes in the presence of 40% dilute sulphuric acid and 1% H₂SO₄ to give the corresponding aldehydes or ketones.

Rosenmund reduction: Aldehydes can be prepared by the hydrogenation of acid chloride, in the presence of palladium supported by barium sulphate. This reaction is called Rosenmund reduction.

Stephen’s reaction: When alkylcyanides are reduced using SnCl₂ / HCl, imines are formed, which on hydrolysis gives corresponding aldehyde. This reaction is called Stephen’s reaction.

Selective reduction of cyanides: Diisobutyl aluminium hydride (DIBAL -H) selectively reduces the alkyl cyanide to form imines which on hydrolysis gives aldehydes.

Etard reaction: When chromylchloride is used as an oxidising agent, toluene gives benzaldehyde. This reaction is called Etard reaction.

Gattermann – Koch reaction: In this reaction, carbon monoxide and HCl generate formyl cation intermediate, which attacks the aromatic ring to form corresponding aldehydes.

Urotropine: Formaldehyde reacts with ammonia to form hexa methylene tetramine, which is also known as Urotropine.

Uses of Urotropine:

• Urotropine is used as a medicine to treat urinary infection.
• Nitration of Urotropine under controlled condition gives an explosive RDX (Research and development explosive). It is also called cyclonite or cyclotri methylene trinitramine.

Popoff s rule: It states that during the oxidation of an unsymmetrical ketone, a (C-CO) bond is cleaved in such a way that the keto group stays with the smaller alkyl group.

Clemmensen reduction: Aldehydes and Ketones when heated with zinc amalgam and concentrated hydrochloric acid gives hydrocarbons. This reduction is called Clemmensen reduction.

Wolf – Kishner reduction: Aldehydes and Ketones when heated with hydrazine and sodium ethoxide, hydrocarbons are formed. This reduction is called Wolf – Kishner reduction.

Aldol condensation: In the presence of bases like NaOH, or KOH, two molecules of an aldehyde or ketone having α – hydrogen add together to give (β- hydroxyl aldehyde (aldol) or β – hydroxyl ketone (ketol). This reaction is called aldol condensation reaction.

Crossed aldol condensation: Aldol condensation can also take place between two different aldehydes or ketones or between one aldehyde and one ketone such an aldol condensation is called crossed aldol condensation.

Claisen – Schmidt Condensation: Benzaldehyde condenses with aliphatic or methyl ketone in the presence of dil. alkali at room temperature to form unsaturated aldehyde or ketone. This type of reaction is called Claisen – Schmidt condensation.

Cannizaro reaction: In the presence of concentrated aqueous alkali, aldehydes which do not have a – hydrogen atom under of self oxidation and reduction to give a mixture of alcohol and a salt of carboxylic acid. This reaction is called Cannizaro reaction.

Crossed Cannizaro reaction: When Cannizaro reaction takes place between two different aldehydes (neither containing an a – hydrogen atom), the reaction is called as cross cannizaro reaction.

Benzoin condensation: This reaction involves the treatment of an aromatic aldehyde with alcoholic KCN. The products are hydroxyl ketone.

Perkin’s reaction: When an aromatic aldehyde is heated with an aliphatic acid anhydride in the presence of the sodium salt of the acid corresponding to the anhydride, condensation takes place and an a, p unsaturated acid is obtained. This reaction is known as Perkin’s reaction.

Knoevenagal reaction: Benzaldehyde condenses with malonic acid in the presence of pyridine forming cinnamic acid is called Knoevenagal reaction or condensation.

Schiff’s base: Aromatic aldehydes react with primary amines in the presence of an acid to form schiff’s base.

Tollens Reagent Test: Tollens reagent is an ammonical silver nitrate solution. When an aldehyde is warmed with Tollens reagent a bright silver mirror is produced due to the formation of silver metal. This reaction is also called silver mirror test for aldehydes.

Fehlings solution Test: Fehlings solution is prepared by mixing equal volumes of Fehlings solution ‘A’ containing aqueous copper sulphate and Fehlings solution ‘B’ containing alkaline solution of sodium potassium tartarate (Rochelle salt). When aldehyde is warmed with Fehlings solution deep blue colour solution is changed to red precipitate of cuprous oxide.

Benedict’s solution Test: Benedicts solution is a mixture of CuSO₄ + sodium citrate + NaOH. Cu²⁺ is reduced by aldehyde to give red precipitate of cuprous oxide.

Schiffs’ reagent Test: Dilute solution of aldehydes when added to schiffs’ reagent (Rosaniline hydrochloride dissolved in water and its red colour decolourised by passing S02) yields its red colour. This is known as Schiffs’ test for aldehydes. Ketones do not give this test. Acetone however gives a positive test but slowly.

Formalin: 40% aqueous solution of formaldehyde is called formalin. It is used for preserving biological specimens

Uses of Acetaldehyde:

• Acetaldehyde is used for silvering of mirrors
• Paraldehyde is used in medicine as a hypnotic
• Acetaldehyde is used in the commercial preparation of number of organic compounds like ‘ acetic acid, ethyl acetate etc.,

Uses of Acetone:

• Acetone is used as a solvent, in the manufacture of smokeless powder (cordite).
• It is used as a nail polish remover.
• It is used in the preparation of sulphonal, a hypnotic.
• It is used in the manufacture of thermosoftening plastic Perspex.

Uses of Benzaldehyde:

• as a flavoring agent
• in perfumes
• in dye intermediates
• as starting material for the synthesis of several other organic compounds like cinnamaldehyde, cinnamic acid, benzoyl chloride etc.

Uses of Aromatic Ketones:

• Acetophenone has been used in perfumery and as a hypnotic under the name hyphone.
• Benzophenone is used in perfumery and in the preparation of benzhydrol drop.

Carboxylic acids: An organic compounds containing a carboxylic functional group, – COOH are called carboxylic acids. The Carboxyl group is the combination of carbonyl group and the hydroxyl group.

Vinegar: It is a 6% to 8% solution of acetic acid in water.

Glacial acetic acid: Pure acetic acid is called glacial acetic acid. Because it forms ice like crystal when cooled. When aqueous acetic acid is cooled at 289.5 K, it solidifies and forms ice like crystals, where as water remains in liquid state and removed by filtration. This process is repeated to obtain glacial acetic acid.

Esterification: When carboxylic acids are heated with alcohols in the presence of cone. H₂SO₄ or dry HCl gas esters are formed. The reaction is reversible and is called esterification.

Decarboxylation: Removal of CO₂ from carboxyl group is called as decarboxylation. Carboxylic acids lose carbon-di-oxide to form hydro carbon when their sodium salts are heated with soda lime (NaOH and CaO in the ratio 3:1)

Kolbe’s electrolytic reaction: The aqueous solutions of sodium or potassium salts of carboxylic acid on electrolysis gives alkanes at anode. This reaction is called kolbes electrolysis.

Hell – Volhard – Zelinsky reaction: Carboxylic acids having an a – hydrogen are
halogenated at the α – position on treatment with Cl₂ or Br₂ in the presence of small amount of red phosphorus to form α – halo carboxylic acids. This reaction is known as  Hell – Volhard – Zelinsky reaction (HVZ reaction)

Tests for carboxylic acid group:

• In aqueous solution carboxylic acid turn blue litmus red.
• Carboxylic acids give brisk effervescence with sodium bicarbonate due to the evolution of carbon-di -oxide.
• When carboxylic acid is warmed with alcohol and Con H₂SO₄ it forms an ester, which is detected by its fruity odour.

Functional derivatives of carboxylic acids: Compounds such as acid chlorides,amides,esters etc., are called carboxylic acid derivatives because they differ from a carboxylic acid only in the nature of the group or atom that has replaced the – OH group of carboxylic acid.

Relative reactivity of Acid derivatives: The reactivity of the acid derivatives follows the

Order of reactivity of the acid derivatives with nucleophilic reagent follows the order:
Acid halide > acid anhydride > esters > acid amides

Transesterification: Ester of an alcohol can react with another alcohol in the presence of a mineral acid to give the ester of second alcohol. The interchange of alcohol portions of the esters is termed transesterification.

Ammonolysis: Esters react slowly with ammonia to form amides and alcohol. This reaction is called ammonolysis.

Claisen Condensation: Esters containing at least one a – hydrogen atom undergo self condensation in the presence of a strong base such as sodium ethoxide to form P – keto ester

Hoff mann’s degradation reaction: Amides reacts with bromine in the presence of caustic potash (KOH) to form a primary amine carrying one carbon less than the parent amide. This is called Hoff mann’s degradation reaction.

Uses of Formic acid:

• For the dehydration of hides
• As a coagulating agent for rubber latex
• In medicine for treatment of gout
• As an antiseptic in the preservation of fruit juice

Uses of Acetic acid:

• As table vinegar
• For coagulating rubber latex
• For manufacture of cellulose acetate and poly vinylacetate

Uses of Benzoic acid:

• As food preservative either in the pure form or in the form of sodium benzoate
• In medicine as an urinary antiseptic
• For manufacture of dyes

Uses of Acetyl chloride:

• As acetylating agent in organic synthesis
• In detection and estimation of – OH, – NH₂ groups in organic compounds

Uses of Acetic anhydride:

• Acetylating agent
• In the preparation of medicine like asprin and phenacetin
• For the manufacture plastics like cellulose acetate and poly vinyl acetate.

Uses of Ethyl acetate:

• In the preparation of artificial fruit essences
• As a solvent for lacquers.
• In the preparation of organic synthetic reagent like ethyl acetoacetate.

Uses of Acetamide: Acetamide is used in the preparation of Primary amines.

Flavours of some of the esters are given below:

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 13 Organic Nitrogen Compounds Notes

Nitro Compounds: If one of the hydrogen atom of hydrocarbon is replaced by the -NO-, group, the resultant organic compound is called nitro compound.

Tautomerism: 1° and 2° nitroalkanes, having a-H , also show as equilibrium mixture of two tautomers namely nitro and aci form. Such a isomeric form are collectively called tautomerism.

Nature of Nitro form:

• Less acidic
• Dissolves in NaOH slowly
• Decolourises FeCl₃ solution
• Electrical conductivity is low

Nature of aci form:

• More acidic and also called pseudoacids (or) nitronic acids
• Dissolves in NaOH instantly
• With FeCl₃ gives reddish brown colour
• Electrical conductivity is high

Nef carbonyl synthesis: Nitro alkanes are reacts with potassium hydroxide, followed by hydrolysis they form corresponding aldehyde.

Amine: An organic compound, which containing NH, functional group and they are called amines.

Mendius reaction: The reduction of alkyl or aryl cyanides reaction in which Na / C₂H₅OH is used as a reducing agent is called Mendius reaction.

Hoffmann’s degradation reaction: When Amides are treated with bromine in the presence of aqueous or ethanolic solution of KOH, primary amines with one carbon atom less than the parent amides are obtained.

Gabriel phthalimide synthesis: Gabriel synthesis is used for the preparation of Aliphatic primary amines. Phthalimide on treatment with ethanolic KOH forms potassium salt of phthalimide which on heating with alkyl halide followed by alkaline hydrolysis gives primary amine.

Hoffmann’s ammonolysis: When Alkyl halides (or) benzylhalides are heated with alcoholic ammonia in a sealed tube, mixtures of 1°, 2° and 3° amines and quaternary ammonium salts are obtained.

The boiling point of various amines follows the order,

Order of basic strength in case of alkyl substituted amines in aqueous solution is,

The relative basicity of amines follows the below mentioned order
Alkyl amines > Aralkyl amines > Ammonia > N – Aralkyl amines > Aryl amines

Schotten – Baumann reaction: Aniline reacts with benzoylchloride in the presence of NaOH to give N – phenyl benzamide. This reaction is known as Schotten – Baumann reaction.

Libermann’s nitroso test: Alkyl and aryl secondary amines react with nitrous acid to give N – nitroso amine as yellow oily liquid which is insoluble in water. This reaction is known as Libermann’s nitroso test.

Carbylamine reaction: Aliphatic (or) aromatic primary (only) amines react with chloroform and alcoholic KOH to give isocyanides (carbylamines), which has an unpleasant smell. This reaction is known as carbylamines test.

Mustard oil reaction: When primary amines are treated with carbon disulphide, N – alkyldithio carbonic acid is formed which on subsequent treatment with HgCl2, give an alkyl isothiocyanate.

Diazonium Salts: Aromatic amines on treatment with NaN02 and HC1 gives diazonium salts. They are stable only for a short time.

Sandmeyer reaction: On mixing freshly prepared solution of benzene diazonium chloride with cuprous halides, aryl halides are obtained. This reaction is called Sandmeyer reaction.

Gattermann reaction: Conversion of benzene diazonium chloride into chloro / bromo arenes can also be effected using HC1 or HBr and copper powder. This reaction is called Gattermann reaction.

Baltz – schiemann reaction: When benzene diazonium chloride is treated with fluoroboric acid, benzene diazonium tetra fluoroborate is precipitated which on heating decomposes to give fluorobenzene.

Gomberg reaction: Benzene diazonium chloride in the presence of sodium hydroxide to give
biphenyl. This reaction in known as the Gomberg reaction. , .

Coupling reactions: Benzene diazonium chloride reacts with electron rich aromatic compounds like phenol, aniline to form brightly coloured azo compounds. Coupling generally occurs at the para position. If para position is occupied then coupling occurs at the ortho position.

Thrope nitrile condensation: Self condensation of two molecules of alkyl nitrile (containing a-H atom) in the presence of sodium to form iminonitrile.

Levine and hauser acetylation: The nitriles containing a – hydrogen also undergo condensation with esters in the presence of sodamide in ether to form ketonitriles. This reaction is known as “ Levine and hauser” acetylation.

Cyanomethylation reaction: This reaction involves replacement of ethoxy (OC₂H₅) group by methylnitrile (-CH₂ CN) group and it is called as cyanomethylation reaction.

Uses of nitroalkanes:

• Nitromethane is used as a fuel for cars
• Chloropicrin (CCl₃ NO₂) is used as an insecticide
• Nitroethane is used as a fuel additive and precursor to explosive and they are good solvents for polymers, cellulose ester, synthetic rubber and dyes etc.,
• 4% solution of ethylnitrite in alcohol is known as sweet spirit of nitre and in used as diuretic.

Uses of nitrobenzene:

• Nitrobenzene is used to produce lubricating oils in motors and machinery
• It is used in the manufacture of dyes, drugs, pesticides, synthelic rubber, aniline and explosives like TNT, TNB.

Uses of cyanides and isocyanides:

• Alkyl cyanides are important intermediates in the organic synthesis of larger number of compounds like acids, amides, esters, amines etc.
• Nitriles are used in textile industry in the manufacture of nitrile rubber and also as a solvent particularly in perfume industry.

Cancer Drug: Mitomycin C, and anticancer agent used to treat stomach and colon cancer, contains an aziridine ring. The aziridine functional group participates in the drug’s degradation by DNA, resulting in the death of cancerous cells.

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 14 Biomolecules Notes

Bio chemistry: The field of studying about the chemistry behind the biological processes is called bio chemistry.

Carbohydrates: Carbohydrates are the most abundant organic compounds in every living organism. They are also known as saccharides. In general carbohydrates are hydrates of carbon, containing hydrogen and oxygen in the same ratio as in water. They are also defined as polyhydroxy aldehydes or ketones.

Dextro rotatory: Dextro rotatory compounds rotate the plane of plane polarised light in clockwise direction. Dextro rotatory compounds are represented as D – (+).

Levo rotatory: Levo rotatory compounds rotate the plane of plane polarised light is anticlockwise direction. Levo rotatory compounds are represented as L – (-).

Monosaccharides: Monosaccharides are carbohydrates that cannot be hydrolysed further and are also called simple sugars. Monosaccharides have general formula Cn(H20)n. While there are many monosaccharides known only about 20 of them occur in nature. Some common examples are glucose, fructose, ribose, erythrose.

Glucose: It is a simple sugar. It is present in honey, sweet fruits such as grapes and mangoes etc therefore glucose is also called as grape sugar. Human blood contains about lOOmg/dL of glucose.

Anomers: The conversion of the achiral aldehyde carbon into a chiral one leading the possibility two isomers. These two isomers differ only in the configuration of Cj – carbon. These isomers are called anomers.

Mutarotation: The slow interconversion of a – D glucose and p – D glucose via open chain form untill equilibrium is established giving constant specific rotation (+53°). This phenomenon is called mutarotation.

Epimerisation: Sugar differing in configuration at an asymmetric centre is known as epimers. The process by which one epimer is converted into other is called epimerisation.

Bio chemistry: The field of studying about the chemistry behind the biological processes is called bio chemistry.

Carbohydrates: Carbohydrates are the most abundant organic compounds in every living organism. They are also known as saccharides. In general carbohydrates are hydrates of carbon, containing hydrogen and oxygen in the same ratio as in water. They are also defined as polyhydroxy aldehydes or ketones.

Dextro rotatory: Dextro rotatory compounds rotate the plane of plane polarised light in clockwise direction. Dextro rotatory compounds are represented as D – (+).

Levo rotatory: Levo rotatory compounds rotate the plane of plane polarised light is anticlockwise direction. Levo rotatory compounds are represented as L – (-).

Monosaccharides: Monosaccharides are carbohydrates that cannot be hydrolysed further and are also called simple sugars. Monosaccharides have general formula Cn(H20)n. While there are many monosaccharides known only about 20 of them occur in nature. Some common examples are glucose, fructose, ribose, erythrose.

Glucose: It is a simple sugar. It is present in honey, sweet fruits such as grapes and mangoes etc therefore glucose is also called as grape sugar. Human blood contains about lOOmg/dL of glucose.

Anomers: The conversion of the achiral aldehyde carbon into a chiral one leading the possibility two isomers. These two isomers differ only in the configuration of Cj – carbon. These isomers are called anomers.

Mutarotation: The slow interconversion of a – D glucose and p – D glucose via open chain form untill equilibrium is established giving constant specific rotation (+53°). This phenomenon is called mutarotation.

Epimerisation: Sugar differing in configuration at an asymmetric centre is known as epimers. The process by which one epimer is converted into other is called epimerisation.

Bio chemistry: The field of studying about the chemistry behind the biological processes is called bio chemistry.

Carbohydrates: Carbohydrates are the most abundant organic compounds in every living organism. They are also known as saccharides. In general carbohydrates are hydrates of carbon, containing hydrogen and oxygen in the same ratio as in water. They are also defined as polyhydroxy aldehydes or ketones.

Dextro rotatory: Dextro rotatory compounds rotate the plane of plane polarised light in clockwise direction. Dextro rotatory compounds are represented as D – (+).

Levo rotatory: Levo rotatory compounds rotate the plane of plane polarised light is anticlockwise direction. Levo rotatory compounds are represented as L – (-).

Monosaccharides: Monosaccharides are carbohydrates that cannot be hydrolysed further and are also called simple sugars. Monosaccharides have general formula Cn(H20)n. While there are many monosaccharides known only about 20 of them occur in nature. Some common examples are glucose, fructose, ribose, erythrose.

Glucose: It is a simple sugar. It is present in honey, sweet fruits such as grapes and mangoes etc therefore glucose is also called as grape sugar. Human blood contains about lOOmg/dL of glucose.

Anomers: The conversion of the achiral aldehyde carbon into a chiral one leading the possibility two isomers. These two isomers differ only in the configuration of Cj – carbon. These isomers are called anomers.

Mutarotation: The slow interconversion of a – D glucose and p – D glucose via open chain form untill equilibrium is established giving constant specific rotation (+53°). This phenomenon is called mutarotation.

Epimerisation: Sugar differing in configuration at an asymmetric centre is known as epimers. The process by which one epimer is converted into other is called epimerisation.

Fructose: Fructose is another commonly known monosaccharide having the same molecular formula as glucose. It is laevorotatory and a ketohexose. It is present abundantly in fruits and hence it is also called as fruit sugar.

Disaccharides: They are sugars that yield two molecules of monosaccharides on hydrolysis. This reaction is usually catalysed by dilute acid or enzyme. In disaccharides two monosaccharides are linked by oxide linkage called glycosidic linkage.

Invert sugar: During hydrolysis of sucrose the optical rotation of the reaction mixture changes from dextro to levo. Hence, sucrose is also called invert sugar.

Polysaccharides: Polysaccharides consist of large number of monosaccharide units bonded together by glycosidic bonds and are the most common form of carbohydrates. Since, they do not have sweet taste polysaccharides are called as non-sugars. They form linear and branched chain molecules.

Starch: Starch is used for energy storage in plants. Potatoes, com, wheat and rice are the rich sources of starch. It is a polymer of glucose in which glucose molecules are lined by a(l,4) glycosidic bonds. Starch can be separated into two fractions namely, water soluble amylose and water insoluble amylopectin. Starch contains about 20 % of amylase and about 80% of amylocpectin.

Cellulose : Cellulose is the major constituent of plant cell walls. Cotton is almost pure cellulose. On hydrolysis cellulose yields D-glucose molecules. Cellulose is a straight chain polysaccharide. The glucose molecules are linked by P(l,4) glycosidic bond.

Glycogen: Glycogen is the storage polysaccharide of animals. It is present in the liver and muscles of animals. Glycogen is also called as animal starch. On hydrolysis it gives glucose molecules.

Importance of carbohydrates:

1. Carbohydrates, widely distributed in plants and animals, acts mainly as energy sources and structural polymers.
2. Carbohydrate is stored in the body as glycogen and in plant as starch.
3. Carbohydrates such as cellulose which is the primary components of plant cell wall, is used to make paper, furniture (wood) and cloths (cotton)
4. Simple sugar glucose serves as an instant source of energy.
5. Ribose sugars are one of the components of nucleic acids.
6. Modified carbohydrates such as hyaluronate (glycosaminoglycans) act as shock absorber and lubricant.

Proteins: Proteins are most abundant biomolecules in all living organisms. The term protein is derived from Greek word “proteious” meaning primary or holding first place.

Amino acids: Amino acids are compounds which contain an amino group and a carboxylic acid group.

Isoelectric point: At a specific pH value the net charge of an amino acid is neutral is called isoelectric point.

Peptide bond: The carboxyl group of the first amino acid react with the amino group of the second amino acid to give an amide linkage between these amino acids. This amide linkage is called peptide bond.

Denaturation: The process of protein losing its higher order structure without losing the primary structure is called denaturation.

Importance of proteins:

1. All biochemical reactions occur in the living systems are catalysed by the catalytic proteins called enzymes.
2. Proteins such as keratin, collagen acts as structural back bones.
3. Proteins are used for transporting molecules (Haemoglobin), organelles (Kinesins) in the cell and control the movement of molecules in and out of the cells (Transporters). ‘
4. Antibodies help the body to fight various diseases
5. Proteins are used as messengers to coordinate many functions. Insulin & glucagon controls the glucose level in the blood.
6. Proteins act as receptors that detect presence of certain signal molecules and activate the proper response.
7. Proteins are also used to store metals such as iron (Ferritin) etc.

Enzymes: There are many biochemical reactions that occur in our living cells. Digestion of food and harvesting the energy from them, and synthesis of necessary molecules required for various cellular functions are examples for such reactions. All these reactions are catalysed by special proteins called enzymes.

Lipids: They are organic molecules that are soluble in organic solvents such as chloroform and methanol and are insoluble in water. The word lipid is derived from the Greek word ‘lipos’ meaning fat.

Biological importance of lipids:

1. Lipids are the integral component of cell membrane. They are necessary of structural integrity of the cell.
2. The main function of triglycerides in animals is as an energy reserve. They yield more energy than carbohydrates and proteins.
3. They act as protective coating in aquatic organisms.
4. Lipids of connective tissue give protection to internal organs.
5. Lipids help in the absorption and transport of fat soluble vitamins.
6. They are essential for activation of enzymes such as lipases.
7. Lipids act as emulsifier in fat metabolism.

Vitamins: Vitamins are small organic compounds that cannot be synthesised by our body but are essential for certain function.

Fat soluble vitamins: These vitamins absorbed best when taken with fatty food and are stored in fatty tissues and livers. These vitamins do not dissolve in water. Hence they are called fat soluble vitamins. Vitamin A, D, E & K are fat-soluble vitamins.

Water soluble vitamins: Vitamins B and C are readily soluble in water.

Nucleic acids: The inherent characteristics of each and every species are transmitted from one generation to the next. It has been observed that the particles in nucleus of the cell are responsible for the transmission of these characteristics. They are called chromosomes and are made up of proteins and another type of biomolecules called nucleic acids.

Nucleosides and nucleotides: The molecule without the phosphate group (molecule consists of sugar and base only) is called a nucleosides. A nucleotide is derived from a nucleoside by the addition of a molecule of phosphoric acid or phosphate unit.

Types of RNA molecules: RNA molecules are classified according to their structure and function into three major types,

1. Ribosomal RNA (r-RNA)
2. Messenger RNA (m-RNA)
3. Transfer RNA (t-RNA) ‘

DNA finger printing: One of the most accurate methods for placing an individual at the scene of a crime has been a fingerprint. With the advent of recombinant DNA technology, a more powerful tool is now available is called DNA finger printing.

Hormones: Hormone is an organic substance that is secreted by one tissue into the blood system and induces a physiological response in other tissues. It is an intercellular signalling molecule.

Samacheer Kalvi 12th Chemistry Notes