Grade 12th passOrganic Chemistry

Why don't ketone give tollens test after all they also have alpha hydrogen?

Suman

6 Years agoGrade 12th pass

2 Answers

Arun

6 Years ago

Tollens' reagent gives a negative test for most ketones, with alpha-hydroxy ketones being one exception. The test rests on the premise that aldehydes are more readily oxidized compared with ketones; this is due to the carbonyl-containing carbon in aldehydes having an attached hydrogen.

Vikas TU

6 Years ago

Dear student
There is misconception that all alpha hydrogen gives Tollens test
Aldehydes give a positive test, and so only alpha-hydroxy ketones that can tautomerize to aldehydes will give a positive Tollen's test
Example – 1-hydroxy-2-propanone, which isomerizes to 2-hydroxypropanol. Most alpha-hydroxy ketones with names that match the pattern 1-hydroxy-2-alkanone will give a positive Tollens' test.

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