Question

IUPAC name of the following compound is:

Answer 1

3-bromobut-3-enoic acid

Answer 2

Solution

1. Structure Analysis:
   The drawn structure is a four‐carbon chain with the following connectivity (from the drawn orientation):

   • Carbon 1 is part of a double bond with carbon 2.
   • Carbon 2 carries a bromine substituent.
   • Carbon 3 is single‐bonded to carbon 4, which bears the carboxyl (–COOH) group.

2. Numbering:
   Since the carboxylic acid group has the highest priority, numbering must start from the –COOH carbon. Reversing the drawn orientation we get:

   • C1: –COOH
   • C2: –CH₂–
   • C3: –CH(Br)=
   • C4: =CH₂

   Note that the double bond is between C3 and C4.

3. IUPAC Name Construction:

   • The parent chain is butenoic acid (4 carbons with a double bond and a carboxyl group).
   • The double bond starts at C3 → "but‑3‑enoic acid".
   • A bromo substituent at C3 gives the prefix "3‑bromo".

Thus, the IUPAC name is:

$$\textbf{3-bromobut-3-enoic acid}$$

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Minimal Explanation:
Number the chain from the –COOH group. The double bond lies between C3 and C4, and Br substituent is on C3. Hence, the name is 3‑bromobut‑3‑enoic acid.