Identify structure of 2,3-dibromo-1-phenylpentane.

Solution

Chemistry ma’am · 3 steps

Build the name from the back: a five-carbon chain first, then phenyl on C1 and Br on C2 and C3.

1. Read the name. Pentane is a five-carbon chain. 1-phenyl puts the benzene ring on C1, the end carbon. 2,3-dibromo puts one Br on C2 and one on C3.

   C₆H₅-C(1)H₂-C(2)HBr-C(3)HBr-C(4)H₂-C(5)H₃

2. Check each option. Number each chain from the end that gives the lowest set of locants. Then compare its name with the one asked.

   Option	Structure	Correct name
   (a)	C₆H₅-CHBr-CH₂-CHBr-CH₂-CH₃	1,3-dibromo-1-phenylpentane
   (b)	C₆H₅-CHBr-CHBr-CH₂-CH₂-CH₃	1,2-dibromo-1-phenylpentane
   (c)	C₆H₅-CH₂-CHBr-CHBr-CH₂-CH₃	2,3-dibromo-1-phenylpentane
   (d)	C₆H₅-CH₂-CH₂-CHBr-CHBr-CH₃	3,4-dibromo-1-phenylpentane

3. So. Only (c) has the ring on C1 with a CH₂ between it and the first Br, and the two Br atoms on C2 and C3.

The idea to keep. To draw a structure from a name, draw the parent chain first, number it, then hang each substituent on its locant. Read the locants back to check.

Answer from the NTA final answer key. Solution by PrepWiser.