Q51P - Organic Chemistry (Mcmurry)

Question

The following ¹H NMR spectrum is that of an alcohol, C₈H₁₀O

. Propose a structure.

Step-by-Step Solution

Answer

The alcohol with the formula C₈H₁₀O that satisfies the ¹H NMR data is 4-methylbenzylalcohol.  

Step 1: 1 H NMR spectrum

Alcohols exhibit characteristic absorption in the ¹H NMR spectrum. Hydrogens on the oxygen bearing carbon atom are deshielded by the electron withdrawing effect of oxygen situated near to it.

Step 2: Structure of the alcohol with the formula C 8 H 10 O

The symmetric doublets at 7.10$\delta$ and 7.17$\delta$  with a relative area of 3.00 indicate that the compound is a para substituted benzene derivative. The signal at 2.32$\delta$ with a relative area of 3.00 indicates that the methyl group is a para substituent. The absorption at 4.50$\delta$ with a relative area of 2.00 indicates a carbon with two hydrogens connected to a hetero atom.

The absorption at 2.43$\delta$ has a relative area of 1.00 is due to the alcoholic proton. Hence, the compound is p-methylbenzyl alcohol. The structure with the absorption values can be given as: