Question

Oil of wintergreen is chemically known as:

• A. Methyl acetate
• B. Methyl salicylate
• C. Ethyl salicylate
• D. Salicylic acid

Hint:

Oil of wintergreen = Methyl salicylate = ester of salicylic acid + methanol. It is commonly used in muscle pain relief balms and has a strong mint-like smell.

Answer 1

The Correct Option is B

Concept: Oil of wintergreen is a naturally occurring aromatic ester obtained mainly from plants of the genus Gaultheria. In organic chemistry, it is identified as an ester formed from salicylic acid and methanol. Esters are typically responsible for characteristic pleasant odors and follow the naming pattern: alkyl group (from alcohol) + carboxylate (from acid).

Step 1: Identifying the main constituent of oil of wintergreen.
Oil of wintergreen is primarily composed of methyl salicylate (about 96–99%). It is the methyl ester of salicylic acid with molecular formula C_8H_8O_3 and contains an ortho-substituted benzene ring with -OH and -COOCH_3 groups.

Step 2: Understanding its formation.
Methyl salicylate is formed by Fischer esterification: \[ \text{Salicylic acid} + \text{Methanol} \xrightarrow{H_2SO_4} \text{Methyl salicylate} + H_2O \] This reaction produces a characteristic aromatic oily liquid with a strong mint-like odor.

Step 3: Evaluating the options.

• Methyl acetate: Simple ester of acetic acid, fruity smell, unrelated to wintergreen.
• Methyl salicylate: Correct compound known as oil of wintergreen.
• Ethyl salicylate: Ethanol-based ester, different compound.
• Salicylic acid: Parent acid, solid and non-aromatic in odor compared to ester.

Step 4: Applications.
Methyl salicylate is used as a flavoring agent and in medicinal pain-relief ointments due to its analgesic and warming properties.