Chemistry Class 12 NCERT Solutions: Chapter 12 Aldehydes Ketones and Carboxylic Acids Part 6

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Q: 9. Write structural formulas and names of four possible aldol condensation products from propanal and butanal. In each case, indicate which aldehyde acts as nucleophile and which as electrophile.

Answer:

(i) Taking two molecules of propanal, one which acts as a nucleophile and the other as an electrophile.

(ii) Taking two molecules of butanal, one which acts as a nucleophile and the other as an electrophile.

(iii) Taking one molecule each of propanal and butanal in which propanal acts as a nucleophile and butanal acts as an electrophile.

(iv) Taking one molecule each of propanal and butanal in which propanal acts as an electrophile and butanal acts as a nucleophile.

Q: 10. An organic compound with the molecular formula forms 2, 4-DNP derivative, reduces Tollens’ reagent and undergoes Cannizzaro reaction. On vigorous oxidation, it gives 1, 2-benzenedicarboxylic acid. Identify the compound.

Answer:

It is given that the compound (with molecular formula ) forms 2, 4-DNP derivative and reduces Tollen’s reagent. Therefore, the given compound must be an aldehyde. Again, the compound undergoes cannizzaro reaction and on oxidation gives 1, 2- benzenedicarboxylic acid. Therefore, the group is directly attached to benzene ring and this benzaldehyde is ortho-substituted. Hence, the compound is 2-ethylbenzaldehyde.

Q 10 1 2-Ethylbenzaldehyde

Q 10 1 2-Ethylbenzaldehyde

Q 10 1 2-Ethylbenzaldehyde

The given reactions can be explained by the following equations.

Q 10 2 1,2 - Benzenedicarboxylic acid

Q 10 2 1,2 - Benzenedicarboxylic Acid

Q 10 2 1,2 - Benzenedicarboxylic acid

Q: 11. An organic compound (A) (molecular formula ) was hydrolysed with dilute sulphuric acid to give a carboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration gives but-1-ene.Write equations for the reactions involved.

Answer:

An organic compound A with molecular formula gives a carboxylic acid (B) and an alcohol (C) on hydrolysis with dilute sulphuric acid. Thus, compound A must be an ester. Further, alcohol C gives acid B on oxidation with chromic acid. Thus, B and C must contain equal number of carbon atoms.

Since compound A contains a total of carbon atoms, each of B and C contain carbon atoms.

Again, on dehydration, alcohol C gives but-1-ene. Therefore, C is of straight chain and hence, it is butan-1-ol.

On oxidation, Butan-1-ol gives butanoic acid. Hence, acid B is butanoic acid. Hence, the ester with molecular formula is butylbutanoate.

All the given reactions can be explained by the following equations.

Q 11 Dehydration Oxidation and Butanoic Acid

Q 11 Dehydration Oxidation and Butanoic Acid

Q 11 Dehydration Oxidation and Butanoic Acid