Q 14-14-59 Ea - Organic Chemistry (Mcmurry)

Question

Hydrocarbon A, , has a UV absorption at ${\mathrm{\lambda }}_{\max }$=236nm and gives hydrocarbon B, C₁₀H₁₈, on catalytic hydrogenation. Ozonolysis of A, followed by zinc/acetic acid treatment, yields the following diketo dialdehyde:

a) Propose two possible structures for A.

Step-by-Step Solution

Answer

The two proposed structures are

Finding degree of unsaturation

In the analysis of  the molecular formula of organic molecules, the degree of unsaturation is a calculation that determines the total numbers of rings and pi bonds in the system. For finding out the DOU, you can use formula,

$$\begin{gathered} \mathrm{Degree} \mathrm{of} \mathrm{unsaturation}=\frac{1}{2}\times (2+2\times \mathrm{C}-\mathrm{H}+\mathrm{N}-\mathrm{X}) \\ \mathrm{Degree} \mathrm{of} \mathrm{unsaturation}=\frac{1}{2}\times (2+2\times 10-14+0-0) \\ \mathrm{Degree} \mathrm{of} \mathrm{unsaturation}=\frac{1}{2}\times (2+2\times 10-14+0-0) \\ \mathrm{Degree} \mathrm{of} \mathrm{unsaturation}=\frac{1}{2}\times (22-14) \\ \mathrm{Degree} \mathrm{of} \mathrm{unsaturation}=4 \end{gathered}$$

From the formula , degree of saturation for A comes out to be 4 and  as you can see that  the ozonolysis product contains all the carbons and di-keto dialdehyde are there, so one can  say, there are 2 rings and 2 double bonds in A.

Prediction of two structures

Two structures which can be in agreement with the information drawn above come out to be,