Q18-63E - Organic Chemistry (Mcmurry)

Question

Disparlure, ${\mathbf{C}}_{19}{\mathbf{H}}_{38}\mathbf{O}$, is a sex attractant released by the female gypsy   moth, Lymantria dispar. The  ${}^1\mathrm{H}$ NMR spectrum of disparlure shows a   large absorption in the alkane region, 1 to 2 d, and a triplet at 2.8 d. Treatment of disparlure, first with aqueous acid and then with ${\mathbf{KMnO}}_4$,  yields two carboxylic acids identified as undecanoic acid and 6-methyl- heptanoic acid. ( ${\mathbf{KMnO}}_4$,cleaves 1, 2-diols to yield carboxylic acids).  Neglecting stereochemistry, propose a structure for disparlure. The actual compound is a chiral molecule with 7R, 8S stereochemistry.   Draw disparlure, showing the correct stereochemistry.

Step-by-Step Solution

Answer

The answer is

Step-by-step Solution

The stereochemistry of the compound is the orientation of bonds of atoms in compounds in space. The stereochemistry determines the reactivity of compounds.

The Potassium permanganate is an important reagent for the oxidation reactions. It can be used for the oxidation of epoxide to carboxylic acids.

Step 1: Explanation

Given, the molecular formula of Displature is ${\mathbf{C}}_{19}{\mathbf{H}}_{38}\mathbf{O}$

The ${}^1\mathrm{H}$ NMR spectrum shows that the compound contains one degree of unsaturation.

The peak at 2.8$\mathrm{\delta }$ identifies an epoxide ring.

The reaction of Displature with aqueous acid and potassium permanganate is as shown below.

                    6-Methyl heptanoic acid                                    Undecanoic acid

Hence, the structure with correct stereochemistry is as shown below.