Question

Predict the products formed when cyclopentanecarbaldehyde reacts with the following reagents.

(a) PhMgBr, then H₃O⁺

(b) Tollens reagent

(c) semicarbazide and weak acid

(d) excess ethanol and acid

(e) propane-1-3-diol, H⁺

(f) zinc amalgam and dilute hydrochloric acid

Short answer

The structure of cyclopentanecarbaldehyde is shown below.

cyclopentanecarbaldehyde

Step-by-step solution

Cyclopentanecarbaldehyde

The structure of cyclopentanecarbaldehyde is shown below.

cyclopentanecarbaldehyde

Clemmensen Reduction

Aldehydes and ketones on being reduction with zinc amalgam (Zn-Hg) and concentrated hydrochloric acid (HCL) give hydrocarbons. This is known as Clemmensen reduction.

Prediction of the products

(a) Cyclopentanecarbaldehyde on treatment with phenylmagnesium bromide in presence of an acidic catalyst H⁺ givesthe product as cyclopentyl(phenyl)methanol.

reaction a

(b) Cyclopentanecarbaldehyde on treatment with tollens reagent to givethe products as silver mirror, ammonia and cyclopentanecarboxylic acid.

reaction b

(c) Cyclopentanecarbaldehyde on treatment with hydrazinecarboxamide in presence of an weak acid givesthe product as 2-(cyclopentylmethyl)hydrazinecarboxamide.

reaction c

(d) Cyclopentanecarbaldehyde on treatment with excess ethanol and acid give sthe product as (diethoxymethyl)cyclopentane.

reaction d

(e) Cyclopentanecarbaldehyde on treatment with propane-1,3-diol in presence of an acidic catalyst H⁺ givesthe product as 2-cyclopentyl-1,3-dioxane.

reaction e

(f) Cyclopentanecarbaldehyde on treatment with amalgamated zinc (zinc treated with mercury) and hydrochloric aacid gives the product as methylcyclopentane

reaction f