Chapter 11, Problem 11.36P

What alkynes give each of the following ketones as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ and ${\text{HgSO}}_{\text{4}}$.

a. b. c. d.

Interpretation Introduction

(a)

Interpretation: The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ 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 11.36P

The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ are $\text{pent}-1-\text{yne}$ and $\text{pent}-2-\text{yne}$.

Explanation of Solution

The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ are shown as,

Figure 1

The terminal alkynes, $\text{pent}-1-\text{yne}$ and $\text{pent}-2-\text{yne}$ 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 $2-\text{pentanone}$ as the desired product.

Conclusion

The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ are $\text{pent}-1-\text{yne}$ and $\text{pent}-2-\text{yne}$.

Interpretation Introduction

(b)

Interpretation: The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ 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 11.36P

The alkyne that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ is ethynylcyclohexane.

Explanation of Solution

The alkyne that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ is shown as,

Figure 2

The terminal alkyne, ethynylcyclohexane 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 $1-\text{cyclohexylethanone}$ as the desired product.

Conclusion

The alkyne that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ is ethynylcyclohexane.

Interpretation Introduction

(c)

Interpretation: The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ 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 11.36P

The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ are $\text{hex}-2-\text{yne}$ and $\text{hex}-3-\text{yne}$.

Explanation of Solution

The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ are shown as,

Figure 3

The terminal alkynes, $\text{hex}-2-\text{yne}$ and $\text{hex}-3-\text{yne}$ 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 $\text{hexan}-3-\text{one}$ as the desired product.

Conclusion

The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ are $\text{hex}-2-\text{yne}$ and $\text{hex}-3-\text{yne}$.

Interpretation Introduction

(d)

Interpretation: The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ 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 11.36P

The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ are $\text{but}-1-\text{yne}$ and $\text{but}-2-\text{yne}$.

Explanation of Solution

The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ are shown as,

Figure 4

The terminal alkynes, $\text{but}-1-\text{yne}$ and $\text{but}-2-\text{yne}$ 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 $\text{butan}-2-\text{one}$ as the desired product.

Conclusion

The alkynes that forms the given ketone as the only product after hydration with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{2}}{\text{SO}}_4$ (strong acid) and ${\text{HgSO}}_{\text{4}}$ are $\text{but}-1-\text{yne}$ and $\text{but}-2-\text{yne}$.