When the alkyne ${\mathrm{CH}}_3-C\equiv C-{\mathrm{CH}}_3$ is treated with ozone followed by water, how many carboxylic acid products are formed?

• A. $2$
• B. $3$
• C. $0$
• D. $1$

Answer: (A)

Verified step by step guidance

1. Identify the structure of the alkyne given: CH3-C\equiv C-CH3, which is 2-butyne, a symmetrical internal alkyne with methyl groups on both ends.
2. Recall the reaction of alkynes with ozone (O3) followed by water (H2O), which is an oxidative cleavage similar to ozonolysis of alkenes but results in carboxylic acids or CO2 depending on the substituents.
3. Break the triple bond between the two carbons and replace each alkyne carbon with a carboxylic acid group (-COOH) if it is bonded to an alkyl group; if bonded to hydrogen, it forms CO2.
4. Since both carbons of the triple bond are bonded to methyl groups (alkyl substituents), each side will form a carboxylic acid group, resulting in two identical carboxylic acid molecules.
5. Conclude that the number of carboxylic acid products formed is 2, corresponding to the two identical carboxylic acid molecules derived from the cleavage.