Question

how many monobromo derivatives are possible for 3,5 dibromo heptane

Answer 1

5

Answer 2

To determine the number of monobromo derivatives, we need to identify the number of unique hydrogen atoms in 3,5-dibromoheptane that can be substituted by a bromine atom.

The structure of 3,5-dibromoheptane is: $\text{CH}_3 - \text{CHBr} - \text{CH}_2 - \text{CHBr} - \text{CH}_2 - \text{CH}_2 - \text{CH}_3$

We examine the hydrogens on each carbon that has them:

1. C1 ($\text{CH}_3$): All 3 hydrogens are equivalent. Substitution yields 1,3,5-tribromoheptane.
2. C3 ($\text{CH}_2$): Both hydrogens are equivalent. Substitution yields 3,3,5-tribromoheptane.
3. C5 ($\text{CH}_2$): Both hydrogens are equivalent. Substitution yields 3,5,5-tribromoheptane.
4. C6 ($\text{CH}_2$): Both hydrogens are equivalent. Substitution yields 3,5,6-tribromoheptane.
5. C7 ($\text{CH}_3$): All 3 hydrogens are equivalent. Substitution yields 3,5,7-tribromoheptane.

The parent molecule is asymmetric. The environments of hydrogens on C1, C3, C5, C6, and C7 are all chemically distinct. Therefore, there are 5 possible monobromo derivatives.