Why hydrocarbons are considered, as parent organic compounds?

Chapter 12

HYDROCARBONS

SOLVED TEST YOURSELFS Test Yourself 12.1 (HYDROCARBONS)

  1. No. i. Why hydrocarbons are considered, as parent organic compounds?

Answer. Hydrocarbons are regarded as the parent organic compounds because other organic compounds are considered to be derived from then by replacement of one or more hydrogen atoms by other atoms or group of atoms. For example, by replacing hydrogen atom with hydroxyl group alcohol is produced.

CH3-H              CH3-OH

CH3-CH2-H         CH3CH2-OH

By replacing hydrogen atom with -NH2 (amino) group amine is formed.

CH3-CH2-NH

  1. No. ii. What is the difference between a straight and a branched chain?

Answer. Straight chain compounds are those in which carbon atom links with other carbon atoms or other atoms through a single, double or triple bonds forming a straight chain. Branched chain compounds are those, in which there is a branch along a straight chain, such:

H3C-CH2-CH2– CH3                     H3C-CH2-CH2          

Straight chain (n- butane)                                CH3

Branched chain (isobutane)

  1. No.iii. Give the general formula of saturated and unsaturated hydrocarbons.

Answer. The general formula of saturated hydrocarbons is CnH2n+2, while that of unsaturated hydrocarbons having one double bond is CnH2n. Where ‘n’ is the number of carbon atom in one molecule.

  1. No. iv. Define unsaturated hydrocarbons with examples.

Answer. The hydrocarbons in which two carbon atoms are linked by a double or a triple bond are called unsaturated hydrocarbons. The compounds in which two carbon atoms are linked by a double bond are called alkenes. For example, ethane and propene.

H2C=CH2                 H3C-CH=CH2

Ethene                        Propene

These compounds have general formula CnH2n and functional group >C = C<.

The hydrocarbons in which two carbon atoms are linked by a triple bond are called alkynes. For example, ethyne and propyne.

HC≡CH            H3C-O≡CH

Ethyne               Propyne

They   have   general formula   CnH2n-2   and   functional   group

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