Chapter 11, Problem 11.34P

What reagents are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ to each compound?

a. b. c d.

Interpretation Introduction

(a)

Interpretation: The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are to be predicted.

Concept introduction: A terminal alkyne reacts with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ to form a ketone. In this case, hydrogen atom and $\text{OH}$ will get attach to the less substituted carbon atom to form a stable carbocation.

Answer to Problem 11.34P

The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$.

Explanation of Solution

The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are shown as,

Figure 1

The terminal alkyne, $3,3-\text{diethylpent}-1-\text{yne}$ reacts with the reagents ${\text{H}}_{\text{2}}\text{O}$, ${\text{HgSO}}_{\text{4}}$ in the presence of strong acid ${\text{H}}_{\text{2}}{\text{SO}}_4$ to form $3,3-\text{diethylpentan}-2-\text{one}$ as the desired product.

Conclusion

The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$.

Interpretation Introduction

(b)

Interpretation: The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are to be predicted.

Concept introduction: A stepwise procedure of transforming an alkyne into a carbonyl group is known hydroboration-oxidation reaction. In a hydroboration-oxidation reaction, a terminal alkyne reacts with ${\text{R}}_{\text{2}}\text{BH}$ followed by ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$, ${}^{-}\text{OH}$ to form an aldehyde.

Answer to Problem 11.34P

The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are ${\text{R}}_{\text{2}}\text{BH}$ followed by ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$, ${}^{-}\text{OH}$.

Explanation of Solution

The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are shown as,

Figure 2

The terminal alkyne, $3,3-\text{diethylpent}-1-\text{yne}$ reacts with the reagents ${\text{R}}_{\text{2}}\text{BH}$ followed by ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$, ${}^{-}\text{OH}$ to form $3,3-\text{diethylpentanal}$ as the desired product. In this case, hydrogen atom and $\text{OH}$ will get attach to the more substituted carbon atom followed by oxidation to form the desired aldehyde.

Conclusion

The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are ${\text{R}}_{\text{2}}\text{BH}$ followed by ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$, ${}^{-}\text{OH}$..

Interpretation Introduction

(c)

Interpretation: The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are to be predicted.

Concept introduction: The ellectrophillic reaction which involves the reaction of an alkene or alkyne with $\text{HCl}$ or $\text{HBr}$ to form a corresponding haloalkane is known as hydrohalogenation reaction.

Answer to Problem 11.34P

The reagent that is needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound is hydrochloric acid.

Explanation of Solution

The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are shown as,

Figure 3

The terminal alkyne, $3,3-\text{diethylpent}-1-\text{yne}$ reacts with two equivalents of $\text{HCl}$ to form $2,2-\text{dicholoro}-3,3-\text{diethylpentane}$ as the desired product. In this case, two equivalents of $\text{HCl}$ is added to the reactant though Markonikov’s rule to form the desired haloalkane.

Conclusion

The reagent that is needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound is hydrochloric acid.

Interpretation Introduction

(d)

Interpretation: The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are to be predicted.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. The nucleophilic reaction that consists of bimolecular as well as bond-making and bond-breaking steps is termed as ${\text{S}}_{\text{N}}\text{2}$ reactions. This is a one-step reaction in which both nucleophile and substrate participate in the rate determining step.

Answer to Problem 11.34P

The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are ${\text{NaNH}}_{\text{2}}$ and ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{Cl}$.

Explanation of Solution

The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are shown as,

Figure 4

The terminal alkyne, $3,3-\text{diethylpent}-1-\text{yne}$ reacts with the strong base, sodium amide $\left({\text{NaNH}}_{\text{2}}\right)$ followed by ethyl chloride, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{Cl}$ to form $5,5-\text{diethylhept}-3-\text{yne}$ as the desired product. In this case, an alkyne reacts with the strong base ${\text{NaNH}}_{\text{2}}$ which abstracts a hydrogen atom to form a carbanion. Then, this carbanion reacts with ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{Cl}$ to form the desired product.

Conclusion

The reagents that are needed to convert ${\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\right)}_{\text{3}}\text{CC}\equiv \text{CH}$ into the given compound are ${\text{NaNH}}_{\text{2}}$ and ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{Cl}$.