Chemistry Class 12 NCERT Solutions: Chapter 12 Aldehydes Ketones and Carboxylic Acids Part 5

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Q: 7. Which of the following compounds would undergo aldol condensation, which the Cannizzaro reaction and which neither? Write the structures of the expected products of aldol condensation and Cannizzaro reaction.

(i) Methanal

(ii) 2-Methylpentanal

(iii) Benzaldehyde

(iv) Benzophenone

(v) Cyclohexanone

(vi) 1-Phenylpropanone

(vii) Phenylacetaldehyde

(viii) Butan-1-ol

(ix) 2, 2-Dimethylbutanal

Answer:

Aldehydes and ketones having at least one α-hydrogen undergo aldol condensation. The compounds (ii) 2−methylpentanal, (v) cyclohexanone, (vi) 1-phenylpropanone, and (vii) Phenylacetaldehyde contain one or more α-hydrogen atoms. Therefore, these undergo aldol condensation.

Aldehydes having no α-hydrogen atoms undergo Cannizzaro reactions. The compounds (i) Methanal, (iii) Benzaldehyde, and (ix) 2, 2-dimethylbutanal do not have any α-hydrogen. Therefore, these undergo cannizzaro reactions.

Compound (iv) Benzophenone is a ketone having no α-hydrogen atom and compound (viii) Butan-1-ol is an alcohol. Hence, these compounds do not undergo either aldol condensation or cannizzaro reactions.

Aldol Condensation:

(ii)

Q 7 Ans ii Adol Condensation

Q 7 Ans Ii Adol Condensation

Q 7 Ans ii Adol Condensation

(v)

Q 7 Ans v Adol Condensation

Q 7 Ans v Adol Condensation

Q 7 Ans v Adol Condensation

(vi)

Q 7 Ans vi Adol Condensation

Q 7 Ans Vi Adol Condensation

Q 7 Ans vi Adol Condensation

(vii)

Q 7 Ans vii Adol Condensation

Q 7 Ans Vii Adol Condensation

Q 7 Ans vii Adol Condensation

Cannizzaro Reaction

(i)

Q 7 Ans i Cannizzaro Reaction

Q 7 Ans I Cannizzaro Reaction

Q 7 Ans i Cannizzaro Reaction

(iii)

Q 7 Ans iii Cannizzaro Reaction

Q 7 Ans Iii Cannizzaro Reaction

Q 7 Ans iii Cannizzaro Reaction

(ix)

Q 7 Ans ix Cannizzaro Reaction

Q 7 Ans Ix Cannizzaro Reaction

Q 7 Ans ix Cannizzaro Reaction

Q: 8. How will you convert ethanal into the following compounds?

(i)

(ii)

(iii)

Answer:

(i) On treatment with dilute alkali, ethanal produces 3-hydroxybutanal gives butane-1, 3-diol on reduction.

(ii) On treatment with dilute alkali, ethanal gives 3-hydroxybutanal which on heating produces but-2-enal.

(iii)

When treated with Tollen’s reagent, But-2-enal produced in the above reaction produces but-2-enoic acid.