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From the compounds listed below, how many will give a POSITIVE iodoform test but a NEGATIVE Tollens' test? (a) Ethanal (CH3CHO) (b) Propan-2-one (CH3COCH3) (c) Butan-2-ol (CH3CH(OH)CH2CH3) (d) 4-acetylbenzaldehyde (OHC-C6H4-COCH3) (e) Cyclopropyl methyl ketone (cyclopropane ring bearing a -COCH3 group) (f) A cyclopentanone derivative bearing both an aldehyde (-CHO) and an acetyl (-COCH3) substituent (g) Ethanol (CH3CH2OH) (h) Acetic acid (CH3COOH) (i) Acetophenone (C6H5COCH3)

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

Correct answer: 5

Solution

Compounds (b) propan-2-one, (c) butan-2-ol, (e) cyclopropyl methyl ketone, (g) ethanol, and (i) acetophenone each give iodoform+ but Tollens'-. That is 5 compounds.

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