Question

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

(a) CH₃NH₂ , H⁺

(b) excess CH₃OH , H⁺

(c) hydroxylamine and weak acid

(d) ethylene glycol and p-toluenesulfuric acid

(e) phenylhydrazine and weak acid

(f) PhMgBr and then mild H₃O⁺

(g) Tollens reagent

(h) sodium acetlylide, then H₃O⁺

(i) hydrazine, then hot. fused KOH

(j) Ph₃P=CH₂

(k) sodium cyanide

(l) acidic hydrolysis of the product from (k)

Short answer

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

(k)

(l)

Step-by-step solution

Cyclopentanone

The structure for cyclopentanone is shown below.

Cyclopentanone

Imine

Ammonia or primary amine under proper conditions reacts with a ketone or an aldehyde to form an imine.

Acetal

It is a derivative of an aldehyde or a ketone having two alkoxy groups in place of the carbonyl group.

Oxime

A compound containing $\text{C}=\text{N}-\text{OH}$ group, formed by the reaction of a ketone or an aldehyde with hydroxylamine is known as oxime.

Nitriles

The organic compounds containing the cyano group $\text{(}-\text{C}\equiv \text{N)}$ are known as nitriles.

Prediction of the products

(a) Cyclopentanone on treatment with methylamine in presence of an acidic catalyst gives the product as N-cyclopentylidenemethanamine.

reaction a

(b) Cyclopentanone on treatment with methanol in presence of an acidic catalyst gives the product as 1,1-dimethoxycyclopentane.

reaction b

(c) Cyclopentanone on treatment with hydroxylamine in presence of an weak acid gives the product as cyclopentanone oxime.

reaction c

(d) Cyclopentanone on treatment with ethylene glycol in presence of p-toluenesulfuric acid (TsOH) gives the product as 1,4-dioxaspiro[4.4]nonane.

reaction d

(e) Cyclopentanone on treatment with phenyl hydrazine in presence of an weak acid gives the product as 1-cyclopentylidene-2-phenylhydrazine.

reaction e

(f) Cyclopentanone on treatment with phenylmagnesium bromide in presence of a mild ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ givesthe product as 1-phenylcyclopentanol.

reaction f

(g) Ketones do not react with tollens reagent, ${\text{Ag(NH}}_{\text{3}}{{\text{)}}_{\text{2}}}^{\text{+}}{}^{\text{-}}\text{OH}$and hence no reaction takes place.

reaction g

(h) Cyclopentanone on treatment with sodium acetylide in presence of an acidic catalyst gives the product as 1-ethynylcyclopentanol.

reaction h

(i) Cyclopentanone on treatment with hydrazine followed by hot. fused potassium hydroxide gives the product as cyclopentane.

reaction i

(j) Cyclopentanone on treatment with Ph₃P=CH₂ gives the product as methylenecyclopentane.

reaction j

(k) Cyclopentanone on treatment with sodium cyanide (NaCN) gives the product as 1-hydroxycyclopentanecarbonitrile.

reaction k

(l) 1-hydroxycyclopentanecarbonitrile on acid-catalyzed hydration gives the product as 1-hydroxycyclopentanecarboxylic acid.

reaction l