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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. |
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Answer» Solution :(ii) 2-Methylpentanal (V) cyclohexanone, (vi) 1-Phenylpropanone and (vii) Phenylacetaldehyde contain one or more o-hydrogens and hence undergo aldol condensation. The reactions and the structures of the expected products are given below: `underset("2-Methylpentanal")underset(""CH_3)underset(""|)(2CH_3CH_2CH_2-CH-CHO)overset("Dil.NaOH")(RARR)underset("3-Hydroxy-2,4-dimethyl-2-propylheptanal")(overset(7)(C)H_3overset(6)(C)H_2overset(5)(C)H_2-underset(CH_3)underset(|)overset("4 ")(C)H-underset(OH)underset("| ")overset(3)(C)H-underset(CHO)underset("1|")overset(CH_3)overset("2|")(C)-CH_2CH_2CH_3) `  (i) Methanal, (iii) Benezaldelhyde and (ix) 2,2-dimethylbutanal do not contain `alpha`- hydrogen and hence undergo Cannizzaro reaction. The reactions and hte structures of the expected products are given below: (i) `underset("Methanol")(2HCHO)overset("conc.NaOH")(rarr)underset("Methanol")(CH_3OH)+underset("Sodium methanoate")(HCOONA)`  (ix) `underset("2,2-Dimethylbutanal")(CH_3CH_2-underset(CH_3)underset(|)overset(CH_3)overset(|)(C)-CHO)underset(NaOH)overset("conc.")(rarr)underset("2,2-Dimethylbutan-1-ol")(CH_3CH_2-underset(CH_3)underset(|)overset(CH_3)overset(|)(C )-CH_2OH)+underset("Sodium 2,2-dimethylbutanoate")(CH_3CH_2-underset("CH_3)underset(|)overset(CH_3)overset(|)(C )-COONa)` (iv) Benzophenone is a ketone having no `alpha`-hydrogen while (viii) Butan - 1- ol is an alcohol. Both of them NEITHER undergo aldol condensation nor Cannizzaro reaction. |
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