Question

Which of the following compound is wrongly named ?

• A. $C{H}_{3}C{H}_{2}C{H}_2\underset{\underset{Cl}{|}}{C}HCOOH$
  2-Chloropentanoic acid
• B. $C{H}_{3}C\equiv C\underset{\underset{Cl}{|}}{C}HCOOH$
  2-Methylhex-3-enoic acid
• C. $C{H}_{3}C{H}_{2}CH=CHCOC{H}_3$
  Hex-3-en-2-one
• D. $C{H}_3-\underset{\underset{C{H}_3}{|}}{C}HC{H}_{2}C{H}_{2}CHO$
  4-Methylpentanal

Answer 1

The correct option is B $C{H}_{3}C\equiv C\underset{\underset{Cl}{|}}{C}HCOOH$

2-Methylhex-3-enoic acid
As -COOH group has higher priority than alkyne, the correct numbering given by
-X (F, Cl, Br, I) do not have any priority order and considered as alkyl substituents while numbering.
$\stackrel{5}{C}{H}_3-\stackrel{4}{C}\equiv \stackrel{3}{C}-\underset{\underset{Cl}{|}}{\stackrel{2}{C}}H=\stackrel{1}{C}OOH$
2-Methyl-hex-3-enoic acid (wrong)
2-Chloro-pent-3-yn-1-oic acid (correct IUPAC name)