Chapter 9.SE, Problem 37AP

Interpretation Introduction

a)

Interpretation:

How to convert 1-butyne in to butanone is to be shown.

Concept introduction:

Terminal alkynes when hydrated with dilute H₂SO₄ in the presence of HgSO₄ are converted in to enols. The addition of water takes place following Markovnikov regiochemistry. The enols upon tautomerization yield ketones as the product.

To show:

How to convert 1-butyne in to butanone.

Interpretation Introduction

b)

Interpretation:

How to convert 1-butyne in to butanal is to be shown.

Concept introduction:

Terminal alkynes when hydrated using hydroboration-oxidation reaction yield an enol with OH group attached to the terminal carbon as the reaction follows anti-Markovnikov regiochemistry. The enol obtained then tautomerizes to an aldehyde.

To show:

How to convert 1-butyne in to butanal is to be shown.

Interpretation Introduction

c)

Interpretation:

How to convert ethynylbenzene in to propynylbenzene is to be shown.

Concept introduction:

Terminal alkynes are converted in to acetylides by treating with NaNH₂ in liquid ammonia. The acetylides can be converted to higher alkynes by treating with alkyl halides having required number of carbon atoms.

To show:

How to convert ethynylbenzene in to propynylbenzene.

Interpretation Introduction

d)

Interpretation:

How to convert propynylbenzene in to cis-1-propenylbenzene is to be shown.

Concept introduction:

Alkynes can be converted in to the corresponding alkenes by treating with H₂ in the presence of Lindlar catalyst. The hydrogenation occurs with syn stereochemistry giving a cis alkene as the product.

To show:

How to convert 1-propynylbenzene in to 1-propenylbenzene.

Interpretation Introduction

e)

Interpretation:

How to convert 1-butyne in to propanoic acid is to be shown.

Concept introduction:

Alkynes gets cleaved when treated with powerful oxidizing agents like KMnO₄. Internal alkynes give carboxylic acids as products. Terminal alkynes give CO₂ also along with a carboxylic acid.

To show:

How to convert 1-butyne in to propanoic acid.

Interpretation Introduction

f)

Interpretation:

How to convert 1-hexene in to 1-hexyne in two steps is to be shown.

Concept introduction:

Alkenes when treated with bromine yield a dibromo alkane which upon dehydrohalogenation with alc.KOH eliminates two molecules of HBr to yield an alkyne as the product.

To show:

How to convert 1-hexene in to 1-hexyne in two steps