Final answer:
The correct reaction for converting acetamide to methanamine is the Hoffmann hypobromamide reaction, which transforms an amide into a primary amine with one fewer carbon atom. Option number b is correct.
Step-by-step explanation:
The appropriate reaction for converting acetamide to methanamine is the Hoffmann hypobromamide reaction. This reaction involves the conversion of an amide to an amine by reaction with bromine in an alkaline (basic) solution.
Through this process, an amide is treated with bromine and a strong base, producing a primary amine with one fewer carbon atom. The other options mentioned, such as the Carbylamine reaction, are not suitable for the conversion of acetamide to methanamine. The Carbylamine reaction specifically tests for primary amines, while Stephen's reaction and Gabriel-phthalimide synthesis are methods for synthesizing amines, but not for converting an amide to an amine.