CBSE Class 10 Answered

Aliphatic compounds are acyclic or cyclic, not aromatic carbon compounds. Thus, aliphatic compounds are opposite to aromatic compounds. In aliphatic compounds, carbon atoms can be joined together in straight chains, branched chains, or non-aromatic rings (in which case they are called alicyclic). Aliphatic compounds can be saturated, joined by single bonds (alkanes), or unsaturated, with double bonds (alkenes) or triple bonds (alkynes). 

STRUCTURAL ISOMERISM

Isomers can be split into two broad groups – structural (or constitutional) isomers, and stereoisomers which can be split again into three main subgroups: chain isomers, position isomers, and functional group isomers. 

Chain Isomers

Chain isomers are molecules with the same molecular formula, but different arrangements of the carbon ‘skeleton’.

Position Isomers

Position isomers are based on the movement of a ‘functional group’ in the molecule.

Functional Isomers

Also referred to as functional group isomers, these are isomers where the molecular formula remains the same, but the type of functional group in the atom is changed.

STEREOISOMERISM

There are two main types of stereoisomerism – geometric isomerism, and optical isomerism.

Geometric Isomers

Geometric isomerism is actually a term that is ‘strongly discouraged’ by IUPAC (the International Union of Pure & Applied Chemistry), who prefer ‘cis-trans’, or ‘E-Z’ in the specific case of alkenes.

Where like groups are on the same side of the double bond, we call it a cis isomer; where they are on opposite sides we call it a trans isomer.

  Answered by Arvind Diwale | 23 Dec, 2014, 07:05: PM