Chapter 9.SE, Problem 33AP

Interpretation Introduction

a)

Interpretation:

The product formed when 2-hexyne reacts with 2 equivalents of bromine.

Concept introduction:

In addition reactions, alkynes when treated with two molar equivalents of a reagent yield the corresponding alkane or its derivatives as products. With one molar equivalent of a reagent they yield the corresponding alkene or its derivative as the products. The addition to unsymmetrical alkenes follows Markovnikov regiochemistry. The negative part of the reagent adds on to the more highly substituted carbon in triple bond.

To give:

The product formed when 2-hexyne reacts with two molar equivalents of bromine.

Interpretation Introduction

b)

Interpretation:

The product formed when 2-hexyne reacts with 1 equivalent of HBr is to be predicted.

Concept introduction:

In addition reactions, alkynes when treated with two molar equivalents of a reagent yield the derivatives of the corresponding alkane as the product. With one molar equivalent of a reagent they yield a derivative of the corresponding alkene as the product. The addition to unsymmetrical alkenes follows Markovnikov regiochemistry. The negative part of the reagent adds on to the more highly substituted carbon in triple bond.

To predict:

The product formed when 2-hexyne reacts with 1 equivalent of HBr.

Interpretation Introduction

c)

Interpretation:

The product formed when 2-hexyne reacts with 1 equivalent of HBr is to be predicted.

Concept introduction:

In addition reactions, alkynes when treated with excess amount of a reagent yield the derivatives of the corresponding alkane as the product. The addition to unsymmetrical alkenes follows Markovnikov regiochemistry. The negative part of the reagent adds on to the more highly substituted carbon in triple bond.

To predict:

The product formed when 2-hexyne reacts with excess of HBr.

Interpretation Introduction

d)

Interpretation:

The product formed when 2-hexyne reacts with Li in ammonia.

Concept introduction:

Alkynes can be reduced by treatment with hydrogen in the presence of a catalyst. The hydrogenation occurs with anti stereochemistry to give a trans- alkene as product if Li in ammonia is used.

To predict:

The product formed when 2-hexyne reacts with Li in ammonia.

Interpretation Introduction

e)

Interpretation:

The product formed when 2-hexyne reacts with H₂O, H₂SO₄ in the presence of HgSO₄ is to be given.

Concept introduction:

When treated with H₂O, H₂SO₄ in the presence of HgSO₄ alkynes get hydrated to produce enols. The addition of water to unsymmetrical alkynes follows Markonikov regiochemistry while it cannot be applied in the case of symmetrical alkynes. The enols produced then undergo tautomerization to give a ketone as the product.

To predict:

The product formed when 2-hexyne reacts with H₂O, H₂SO₄ in the presence of HgSO₄.