Write the IUPAC names of the compounds i-iv from their given structures.
(i) `overset(1)(C)H_(3)-overset(2)(C)H_(2)-underset(OH)underset("| ")overset("3 ")(CH)-overset(4)(C)H_(2)-overset(5)(C)H_(2)-underset(CH_(3))underset("| ")overset("6 ")(CH)-overset(7)(C)H_(2)-overset(8)(C)H_(3)`
(ii) `underset(6)(C)H_(3)-underset(5)(C)H_(2)-underset(4)overset(O)overset(||)(C)-underset(3)(C)H_(2)-underset(2)overset(O)overset(||)(C)-underset(1)(C)H_(3)`
(iii) `underset(6)(C)H_(3)-underset(5)overset(O)overset(||)(C)-underset(4)(C)H_(2)-underset(3)(C)H_(2)-underset(2)(C)H_(2)-underset(1)(C)OOH`
(iv) `underset(6)(C)H-=underset(5)(C)-underset(4)(C)H=underset(3)(C)H-underset(2)(C)H=underset(1)(C)H_(2)`

Explanation

• The functional group present is an alcohol (OH). Hence the suffix is ‘-ol’.
• The longest chain containing -OH has eight carbon atoms. Hence the corresponding saturated hydrocarbon is octane.
• The -OH is on carbon atom 3. In addition, a methyl group is attached at `6^(th)` carbon.
Hence, the systematic name of this compound is 6-Methyloctan-3-ol.
(ii) The functional group present is ketone `(>C=O)`, hence suffix ‘-one’. Presence of two keto groups is indicated by ‘di’, hence suffix becomes ‘dione’. The two keto groups are at carbons 2 and 4. The longest chain contains 6 carbon atoms, hence, parent hydrocarbon is hexane. Thus, the systematic name is Hexane- 2,4-dione.
(iii) Here, two functional groups namely ketone and carboxylic acid are present. The principal functional group is the carboxylic acid group, hence the parent chain will be suffixed with ‘oic’ acid. Numbering of the chain starts from carbon of – COOH functional group. The keto group in the chain at carbon 5 is indicated by ‘oxo’. The longest chain including the principal functional group has 6 carbon atoms, hence the parent hydrocarbon is hexane. The compound is, therefore, named as 5-Oxohexanoic acid.
(iv) The two `C=C` functional groups are present at carbon atoms 1 and 3, while the `C≡C` functional group is present at carbon 5. These groups are indicated by suffixes ‘diene’ and ‘yne’ respectively. The longest chain containing the functional groups has 6 carbon atoms, hence the parent hydrocarbon is hexane. The name of compound, therefore, is Hexa-1,3- dien-5-yne