Chapter 7, Problem 7.54P

Interpretation Introduction

(a)

Interpretation: The given species are to be arranged in order of increasing nucleophilicity.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. In nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking on the electron deficient carbon atom. The good nucleophiles are strong base whose conjugate acids have high $p{K}_a$ value.

Answer to Problem 7.54P

The order of increasing nucleophilicity is ${}^{-}\text{OH}{<}^{-}{\text{NH}}_2<{\text{CH}}_{\text{3}}{}^{-}$

Explanation of Solution

On moving right to left across a row in periodic table, nucleophilicity as well as the basicity increases. Therefore, the order of increasing nucleophilicity is ${}^{-}\text{OH}{<}^{-}{\text{NH}}_2<{\text{CH}}_{\text{3}}{}^{-}$

Conclusion

The order of increasing nucleophilicity is ${}^{-}\text{OH}{<}^{-}{\text{NH}}_2<{\text{CH}}_{\text{3}}{}^{-}$.

Interpretation Introduction

(b)

Interpretation: The given species are to be arranged in order of increasing nucleophilicity.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. In nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking on the electron deficient carbon atom. The good nucleophiles are strong base whose conjugate acids have high $p{K}_a$ value.

Answer to Problem 7.54P

The order of increasing nucleophilicity is ${\text{H}}_{\text{2}}\text{O}{<}^{-}\text{OH}{<}^{-}\text{SH}$

Explanation of Solution

The size of ${}^{-}\text{SH}$ is greater than that of ${}^{-}\text{OH}$. Therefore, it is more nucleophilic because the nucleophilicity increases with increase in the size of the anion. ${}^{-}\text{OH}$ is more nucleophilic than its conjugate acid ${\text{H}}_{\text{2}}\text{O}$. Therefore, the order of increasing nucleophilicity is ${\text{H}}_{\text{2}}\text{O}{<}^{-}\text{OH}{<}^{-}\text{SH}$

Conclusion

The order of increasing nucleophilicity is ${\text{H}}_{\text{2}}\text{O}{<}^{-}\text{OH}{<}^{-}\text{SH}$.

Interpretation Introduction

(c)

Interpretation: The given species are to be arranged in order of increasing nucleophilicity.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. In nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking on the electron deficient carbon atom. The good nucleophiles are strong base whose conjugate acids have high $p{K}_a$ value.

Answer to Problem 7.54P

The order of increasing nucleophilicity is ${\text{CH}}_{\text{3}}{\text{CO}}_{\text{2}}{}^{-}<{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{O}}^{-}<{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{S}}^{-}$

Explanation of Solution

A solvent in which hydrogen atom is bonded to electronegative $\text{O}$ or $\text{N}$ atom is termed as polar protic solvent. Methanol is a polar protic solvent. In polar protic solvent on moving down the group, basicity increases because the size of anion increases. Sulfur lies below oxygen atom in a periodic table. Thus, nucleophilicity of ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{S}}^{-}$ is higher. The conjugate acid of good nucleophile has high $p{K}_a$ value. The $p{K}_a$ value of conjugate acid of ${\text{CH}}_{\text{3}}{\text{CO}}_{\text{2}}{}^{-}$ has higher value than the $p{K}_a$ value of conjugate acid of ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{O}}^{-}$. Therefore, the order of increasing nucleophilicity is ${\text{CH}}_{\text{3}}{\text{CO}}_{\text{2}}{}^{-}<{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{O}}^{-}<{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{S}}^{-}$.

Conclusion

The order of increasing nucleophilicity is ${\text{CH}}_{\text{3}}{\text{CO}}_{\text{2}}{}^{-}<{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{O}}^{-}<{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{S}}^{-}$.

Interpretation Introduction

(d)

Interpretation: The given species are to be arranged in order of increasing nucleophilicity.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. In nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking on the electron deficient carbon atom. The good nucleophiles are strong base whose conjugate acids have high $p{K}_a$ value.

Answer to Problem 7.54P

The order of increasing nucleophilicity is ${\text{CH}}_{\text{3}}\text{SH}<{\text{CH}}_{\text{3}}\text{OH}<{\text{CH}}_{\text{3}}{\text{NH}}_{\text{2}}$.

Explanation of Solution

The nucleophilicity and basicity are directly related to each other in polar aprotic solvent. Acetone is a polar aprotic solvent.

On moving down the group in a periodic table and left to right in a period, basicity decreases and hence, nucleophilicity decreases. Sulfur lies below oxygen atom and nitrogen lies left to oxygen atom in a periodic table. Thus, the order of increasing nucleophilicity is ${\text{CH}}_{\text{3}}\text{SH}<{\text{CH}}_{\text{3}}\text{OH}<{\text{CH}}_{\text{3}}{\text{NH}}_{\text{2}}$.

Conclusion

The order of increasing nucleophilicity is ${\text{CH}}_{\text{3}}\text{SH}<{\text{CH}}_{\text{3}}\text{OH}<{\text{CH}}_{\text{3}}{\text{NH}}_{\text{2}}$.

Interpretation Introduction

(e)

Interpretation: The given species are to be arranged in order of increasing nucleophilicity.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. In nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking on the electron deficient carbon atom. The good nucleophiles are strong base whose conjugate acids have high $p{K}_a$ value.

Answer to Problem 7.54P

The order of increasing nucleophilicity is ${\text{Cl}}^{-}<{\text{F}}^{-}{<}^{-}\text{OH}$.

Explanation of Solution

The nucleophilicity and basicity are directly related to each other in polar aprotic solvent. Acetone is a polar aprotic solvent.

On moving down the group in a periodic table and left to right in a period, basicity decreases and hence, nucleophilicity decreases. Chlorine lies below fluorine atom and nitrogen lies left to fluorine in a periodic table. Thus, the order of increasing nucleophilicity is ${\text{Cl}}^{-}<{\text{F}}^{-}{<}^{-}\text{OH}$.

Conclusion

The order of increasing nucleophilicity is ${\text{Cl}}^{-}<{\text{F}}^{-}{<}^{-}\text{OH}$.

Interpretation Introduction

(f)

Interpretation: The given species are to be arranged in order of increasing nucleophilicity.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. In nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking on the electron deficient carbon atom. The good nucleophiles are strong base whose conjugate acids have high $p{K}_a$ value.

Answer to Problem 7.54P

The order of increasing nucleophilicity is ${\text{F}}^{-}<{\text{HS}}^{-}<{\text{Cl}}^{-}$.

Explanation of Solution

A solvent in which hydrogen atom is bonded to electronegative $\text{O}$ or $\text{N}$ atom is termed as polar protic solvent. Methanol is a polar protic solvent. In polar protic solvent, on moving down the group and right to left in a periodic table, basicity increases because the size of anion increases. Thus, the order of increasing nucleophilicity is ${\text{F}}^{-}<{\text{HS}}^{-}<{\text{Cl}}^{-}$.

Conclusion

The order of increasing nucleophilicity is ${\text{F}}^{-}<{\text{HS}}^{-}<{\text{Cl}}^{-}$.