Chapter 20, Problem 29A

(a)

Interpretation Introduction

Interpretation:

The given chemical equation is to be completed.

  $\mathrm{H}\mathrm{C}\equiv \mathrm{C}-\mathrm{C}{\mathrm{H}}_3+{\mathrm{H}}_2\to$

Concept Introduction:

Alkynes are acyclic unsaturated hydrocarbons containing at least one carbon-carbon triple bond (CC) and the general molecular formula of alkynes is C_nH_2n-2 (where n = number of carbon atoms). Simplest alkene among all is acetylene C₂H₂ (HCCH)which contains one carbon-carbon triple bond.

Answer to Problem 29A

  $\mathrm{H}\mathrm{C}\equiv \mathrm{C}-\mathrm{C}{\mathrm{H}}_3+{\mathrm{H}}_2\to {\mathrm{H}}_2\mathrm{C}=\mathrm{C}\mathrm{H}-\mathrm{C}{\mathrm{H}}_3$

Explanation of Solution

The chemical reaction where two hydrogen atoms are added to an organic molecule in the presence of catalyst is called hydrogenation reaction.When an alkyne is hydrogenated, two hydrogen atoms are added to the saturated alkyne to form an alkene. This is a type of addition reaction.

  $\mathrm{H}\mathrm{C}\equiv \mathrm{C}-\mathrm{C}{\mathrm{H}}_3+{\mathrm{H}}_2\to {\mathrm{H}}_2\mathrm{C}=\mathrm{C}\mathrm{H}-\mathrm{C}{\mathrm{H}}_3$

(b)

Interpretation Introduction

Interpretation:

The given chemical equation is to be completed.

Concept Introduction:

Alkenes are acyclic or cyclic unsaturated hydrocarbons containing at least one carbon-carbon double bond (C=C) and the general molecular formula C_nH_2n (where n = number of carbon atoms). Simplest alkene among all is ethylene C₂H₄ which contains one carbon-carbon double bond.

Answer to Problem 29A

  

Explanation of Solution

This is an addition reaction between bromine and alkene. Saturated dibromo-alkane is formed in this reaction.

When 2-butene is treated with bromine, 2,3-dibomobutane is formed.

  

(c)

Interpretation Introduction

Interpretation:

The given chemical equation is to be completed.

Concept Introduction:

Alkynes are acyclic unsaturated hydrocarbons containing at least one carbon-carbon triple bond (CC) and the general molecular formula of alkynes is C_nH_2n-2 (where n = number of carbon atoms). Simplest alkene among all is acetylene C₂H₂ (HCCH)which contains one carbon-carbon triple bond.

Answer to Problem 29A

  

Explanation of Solution

When oxidation of alkyne is done, there occurs the formation of carbonyl compound. Terminal alkyne is oxidised to aldehydic group and non-terminal alkyne is converted to keto group. So, when but-2-yne is treated with oxygen, butane-2,3-dione is obtained.