question_answer 8)

Write the IUPAC names of the compounds [(i)-(iv)] from their given structures. (i) \[\overset{1}{\mathop{C{{H}_{3}}}}\,-\overset{2}{\mathop{C{{H}_{2}}}}\,-\underset{\underset{\text{OH}}{\mathop{\text{ }\!\!|\!\!\text{ }}}\,}{\mathop{\overset{3}{\mathop{CH}}\,}}\,-\overset{4}{\mathop{C{{H}_{2}}}}\,-\overset{5}{\mathop{C{{H}_{2}}}}\,\] \[-\underset{\underset{\text{C}{{\text{H}}_{\text{3}}}}{\mathop{\text{ }\!\!|\!\!\text{ }}}\,}{\mathop{\overset{6}{\mathop{CH}}\,}}\,-\overset{7}{\mathop{C{{H}_{2}}}}\,-\overset{8}{\mathop{C{{H}_{3}}}}\,\] (ii) \[\overset{6}{\mathop{C{{H}_{3}}}}\,-\overset{5}{\mathop{C{{H}_{2}}}}\,-\overset{\overset{\text{O}}{\mathop{\text{ }\!\!|\!\!\text{ }\!\!|\!\!\text{ }}}\,}{\mathop{^{4}C}}\,-\overset{3}{\mathop{C{{H}_{2}}}}\,-{{\,}^{2}}\overset{\overset{\text{O}}{\mathop{\text{ }\!\!|\!\!\text{ }\!\!|\!\!\text{ }}}\,}{\mathop{C}}\,-\overset{1}{\mathop{C{{H}_{3}}}}\,\] (iii) \[\overset{6}{\mathop{C{{H}_{3}}}}\,-{{\,}^{5}}\overset{\overset{\text{O}}{\mathop{\text{ }\!\!|\!\!\text{ }\!\!|\!\!\text{ }}}\,}{\mathop{C}}\,-\overset{4}{\mathop{C{{H}_{2}}}}\,-\overset{3}{\mathop{C{{H}_{2}}}}\,-\overset{2}{\mathop{C{{H}_{2}}}}\,-\overset{1}{\mathop{COOH}}\,\] (iv)\[\overset{6}{\mathop{HC}}\,\equiv \overset{5}{\mathop{C}}\,-\overset{4}{\mathop{CH}}\,=\overset{3}{\mathop{CH}}\,-\overset{2}{\mathop{CH}}\,=\overset{1}{\mathop{C{{H}_{2}}}}\,\]

Answer:

(i) The longest chain consists of eight carbon atoms with a functional group as alcohol (-OH) on carbon atom 3. In addition, a methyl group is attached at position 6. Hence, the systematic name of this compound is : 6-Methyloctan-3-ol. (ii) The longest chain consists of six carbon atoms with two functional groups as ketones at carbons 2 and 4. Hence, the systematic name is : Hexane-2,4-dione (iii) The two functional groups namely ketone and carboxylic acids are present. The principal functional group is -COOH and the keto (or oxo) group is the substituent functional group (at position 5). The longest chain including the principal functional group has 6 carbon atoms. Hence, the systematic name is: 5 Oxohexanoic acid. (iv) The longest chain consists of six carbon atomswith two C = C functional group at positions 1 and 3 and one \[C\equiv C\] at position 5. Whenever there is a choice in numbering, the double bond is given preference, therefore, locants for diene are 1 and 3 and for yne is 5. Hence, the systematic name is: Hexa-1, 3-dien-5-yne.