Q.53. - Organic Chemistry

Question

Question: Oximene and myrcene, two hydrocarbons isolated from alfalfa that have the molecular formula ${\mathit{C}}_{\mathbf{10}}{\mathit{H}}_{\mathbf{16}}$ , both yield 2,6-dimethyloctane when treated with  ${\mathit{H}}_{\mathbf{2}}$ and a Pd catalyst. Ozonolysis of oximene forms ${\left(C{H}_3\right)}_{\mathbf{2}}\mathit{C}\mathbf{=}\mathit{O}$ , $\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathbf{=}\mathit{O}$ , $\mathit{C}{\mathit{H}}_{\mathbf{2}}{\left(CHO\right)}_{\mathbf{2}}$ and $\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathit{C}\mathit{O}\mathit{C}\mathit{H}\mathit{O}$. Ozonolysis of myrcene yields ${\left(C{H}_3\right)}_{\mathbf{2}}\mathit{C}\mathit{O}$, $\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathbf{=}\mathit{O}$ (two equiv), and $\mathit{H}\mathit{C}\mathit{O}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{C}\mathit{O}\mathit{C}\mathit{H}\mathit{O}$. Identify the structures of oximene and myrcene.

Step-by-Step Solution

Answer

Answer

Step 1: Oximene

Oximene belongs to the category of monoterpenes. It has different isomers such as  $\mathit{\alpha }$-Oximene, cis- $\mathit{\beta }$ -oximene, and trans-$\mathit{\beta }$-oximene.

Step 2: Myrcene

Myrcene belongs to the category of isoterpenes. It is employed as an intermediate in making perfumes.

Step 3: Structures of oximene and myrcene

The reaction of oximene and myrcene with  $H_2$ in the presence of Pd catalyst leads to the product as shown below.

The hydrogenation reaction indicates that oximene and myrcene contain $3\mathrm{\pi }$  bonds and no rings. 

 

This carbon backbone can be utilized, and the double bonds can be added based on the oxidative cleavage products to obtain the structures of oximene and myrcene.

 

The structure of oximeneis given below.

Structure of oximene from the cleavage products

 

The structure of myrcene is given below.

Structure of myrcene from the cleavage products