Organic Reactions

Let's analyze each reaction:
1. Hydration of alkynes: This reaction leads to the formation of a ketone (for terminal alkynes, it forms an aldehyde, but for internal alkynes, it forms a ketone).
2. Ozonolysis of substituted alkenes: This reaction involves breaking the double bond and forming two carbonyl compounds (typically ketones or aldehydes).
3. Treating nitrite with a Grignard reagent: This reaction produces alcohols, not ketones. Grignard reagents typically react with nitrites to form an alcohol after hydrolysis.
4. Stephen's reaction: This reaction involves reducing nitro compounds to aldehydes, and not ketones.
Therefore, the correct answer is (3) Treating nitrite with a Grignard reagent, as this will not produce a ketone.