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A substance having molecular mass 180 undergoes acetylation with CH3COCl, producing a derivative of molecular mass 390. How many amino groups are present in each molecule of the original substance?

1. 2
2. 5
3. 4
4. 6

Correct answer: 5

Solution

Each acetylation replaces an H with COCH3, a net mass increase of 42. The total increase is 390 - 180 = 210, so 210/42 = 5 groups are acetylated, meaning 5 amino groups.

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