CBSE 2015, Set 2

Question

(a) Write the structures of the main products when acetone ($CH_3 - CO - CH_3$) reacts with the following reagents :
(i) Zn - Hg/conc. HCl
(ii) $H_2N - NHCONH_2/H^+$
(iii) $CH_3MgBr$ and then $H_3O^+$

(b) Arrange the following in the increasing order of their boiling points :
$C_2H_5OH$, $CH_3 - CHO$, $CH_3 - COOH$

(c) Give a simple chemical test to distinguish between the following pair of compounds :
$CH_3CH_2CHO$ and $CH_3CH_2COCH_3$

Edvaya · Accepted Answer

The correct answer is Subjective. **SOLUTION** (a) (i) Acetone undergoes Clemmensen reduction in presence of zinc amalgam and conc. HCl to give Propane. ![Clemmensen Reduction](https://www.edvaya.com/img/55.png) (ii) Acetone reacts with semicarbazide to form semicarbazone. ![Semicarbazone Reaction](https://www.edvaya.com/img/53.png) (iii) Acetone reduces to form tertiary alcohol in presence of Grignard reagent. ![Grignard Reaction](https://www.edvaya.com/img/54.png) (b) Due to extensive hydrogen bonding, carboxylic acids have the highest boiling points among the given compounds. Alcohols, with smaller number of hydrogen bonds, have lesser boiling point. Aldehydes have the least boiling point due to the absence of hydrogen bonding. Hence, in the increasing order of boiling points, the compounds can be arranged as follows: $CH_3-CHO < C_2H_5OH < CH_3-COOH$ (c) 2-Butanone has a methyl group attached to carbonyl carbon unlike Propanal. Hence, it can give iodofom test. ![Iodoform Test Butanone](https://www.edvaya.com/img/56.png)

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Chemistry > Organic Chemistry > Aldehydes Ketones And Carboxylic Acids

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