Online Notes on Chapter=4 ( Carbon and Its compounds) Part 2

This is Online Notes on Chapter=4 ( Carbon and Its compounds) Part 2 for preparation of CBSE BOARD Examination, NTSE etc


=> Homologous Series:

It is series of compounds in which the some functional group substitutes for
the hydrogen in a carbon chain.
E.g., Alcohols – CH3OH, C2H5OH, C3H7OH, C4H9OH

• Have same general formula.

• Any two homologues differ by – CH2 group and difference in molecular
mass is 14μ.

• Have same chemical properties but show gradual change in physical

properties.

=> Nomenclature of Carbon Compounds:

(i) Identify the number of carbon atoms in compounds.

(ii) Functional group is indicated by suffix or prefix.

=> Chemical Properties of Carbon Compounds:
(a) Combustion

CH4 + 2O2   ==Combution==>   CO2 + 2H2O + Heat + Light

• Carbon and its compounds are used as fuels because they burn in air
releasing lot of heat energy.
• Saturated hydrocarbon generally burn in air with blue and non-sooty
flame.

• Unsaturated hydrocarbon burns in air with yellow sooty flame because
percentage of carbon is higher than saturated hydrocarbon which does
not get completely oxidized in air.

(b) Oxidation
Alcohols can be converted to carboxylic acid in presence of oxidizing agent
alkaline KMnO4 (potassium permangnate) or acidic potassium dichromate.

CH3CH2OH   ==Alkaline  KMnO4 or Acidic K2Cr2O7==>    CH3COOH
Ethanol                                                                                       Ethanoic Acid
Unsaturated hydrocarbon add hydrogen in the presence of catalyst palladium
or nickel. Vegetable oils are converted into vegetable ghee using this process. It
is also called hydrogenation of vegetable oils.

(d) Substitution Reaction :

CH4 + Cl2 ==Sunlight==>  CH2Cl  +  HCl

=> Important Carbon Compounds : Ethanol and Ethanoic acid:
Physical Properties of Ethanol:

• Colourless, pleasant smell and burning taste.
• Soluble in water.
• Volatile liquid with low boiling point of 351 K.
• Neutral compound.

Chemical Properties:

(i) Reaction with Sodium :
2Na + CH3CH2OH →  2CH3CH2O-Na+     +      H2
                                        (Sodium Ethoxide)

This reaction is used as a test for ethanol by evolution of H2 gas (Burn with
pop sound).

(ii) Dehydration :

CH3CH2OH  ==Hot Conc. H2SO4==>   CH2 = CH2   +   H2O

Physical Properties of Ethanoic acid:

• Colourless liquid having sour taste and have smell of vinegar.
• Boiling point is 391 K.
• When pure CH3COOH is freezed, it forms colourless ice like solid. So it
is called glacial acetic acid.

Chemical Properties:

(i) Esterification :

This is saponification as soap is prepared by this.

(ii) Reaction with base :

NaOH + CH3COOH      →       CH3COONa      +    H2O
                                                  (Sod. Acetate)

iii) Reaction with carbonates and hydrogen carbonates :

2CH3COOH + Na2CO3   →    2CH3COONa + H2O + CO2

CH3COOH + NaHCO3   →    CH3COONa + H2O + CO2
                                                (Sod. Acetate)

Soaps and Detergents
• Soap is sodium or potassium salt of long chain carboxylic acid. E.g.,
C17H35COO-Na+
• Soaps are effective only in soft water.
• Detergents are ammonium or sulphonate salt of long chain of carboxylic
acid.
• Detergents are effective in both hard and soft water.
Soap molecule has :
(i) Ionic (hydrophyllic) part
(ii) Long hydrocarbon chain (hydrophobic) part

=>Cleansing Action of Soap:
• Most dirt is oily in nature and hydrophobic end attaches itself with dirt
and the ionic end is surrounded with molecule of water. This result in
formation of a radial structure called micelles.
• Soap micelles helps to dissolve dirt and grease in water and cloth gets cleaned.

• The magnesium and calcium salt present in hard water react with soap
molecule to form insoluble product called scum. This scum create
difficulty in cleansing action.
• By use of detergent, insoluble scum is not formed with hard water and
cloths get cleaned effectively.