Chapter 11, Problem 11.1P

Interpretation Introduction

(a)

Interpretation:

For the given reaction, a complete, detailed mechanism is to be drawn, and the major product, ignoring stereochemistry, is to be predicted.

Concept introduction:

An electrophilic addition reaction is an addition reaction where a $\text{π}$ bond is broken and two new $\text{σ}$ bonds are formed. This reaction takes place via a two-step mechanism. Step 1 is an electrophilic addition step, in which the pair of electrons from the electron-rich $\text{π}$ bond forms a bond to the acid’s electron-poor atom. One of the originally double-bonded carbon atoms develops a +1 formal charge, making it a carbocation. Step 2 is a coordination step, whereby the halide forms a bond to the carbocation. In an electrophilic addition of a Bronsted acid to an alkene, the rate-determining step is Step $\text{1}$, the addition of the ${\text{H}}^{\text{+}}$ electrophile. It is identical to the second step of the ${\text{S}}_{\text{N}}\text{1}$ reaction mechanism.

Answer to Problem 11.1P

The complete mechanism for the given reaction is

The major product of the reaction is

Explanation of Solution

The given reaction is

The given reaction occurs in two steps. The electrophilic addition is the first elementary step. The $\text{π}$ electrons of the C=C is an electron-rich species, and the H atom of the acid HCl is an electron-poor species (electrophile). The $\text{π}$ bond breaks heterolytically, and the electron pair forms a bond with the proton of the acid. A carbocation forms as a result. The second elementary step is one of coordination. The conjugate base ${\text{Cl}}^{-}$ acts as a nucleophile to form a bond with the carbocation.

Conclusion

The product of an electrophilic addition reaction is formed as a result of the addition of the two parts of a Bronsted acid across a double bond, replacing one $\text{π}$ bond with two $\text{σ}$ bonds.

Interpretation Introduction

(b)

Interpretation:

For the given reaction, the complete, detailed mechanism is to be drawn, and the major product is to be predicted.

Concept introduction:

An electrophilic addition reaction is an addition reaction where a $\text{π}$ bond is broken and two new $\text{σ}$ bonds are formed. This reaction occurs in two-step mechanism. Step 1 is an electrophilic addition step, in which the pair of electrons from the electron-rich $\text{π}$ bond forms a bond to the acid’s electron-poor atom. One of the originally double-bonded carbon atoms develops a +1 formal charge, making it a carbocation. Step 2 is a coordination step, whereby the halide forms a bond to the carbocation. In an electrophilic addition of a Bronsted acid to an alkene, the rate-determining step is Step $\text{1}$, the addition of the ${\text{H}}^{\text{+}}$ electrophile. It is identical to the second step of the ${\text{S}}_{\text{N}}\text{1}$ reaction mechanism.

Answer to Problem 11.1P

The complete mechanism of the given reaction is

The major product of the reaction is

Explanation of Solution

The given reaction is

The given reaction occurs in two steps. The first elementary step is an electrophilic addition, where the $\text{π}$ electrons of the C=C act as the electron-rich species, and the H atom of the acid HI acts as the electron-poor species (electrophile). A carbocation forms in the first step. The second elementary step is one of coordination, where the conjugate base ${\text{I}}^{-}$ acts as the nucleophile and forms a bond with the carbocation.

Conclusion

The product of an electrophilic addition reaction is formed as a result of the addition of the two parts of a Bronsted acid across a double bond, replacing one $\text{π}$ bond with two $\text{σ}$ bonds.

Interpretation Introduction

(c)

Interpretation:

For the given reaction, the complete, detailed mechanism is to be drawn, and the major product is to be predicted.

Concept introduction:

An electrophilic addition reaction is an addition reaction where a $\text{π}$ bond is broken and two new $\text{σ}$ bonds are formed. This reaction occurs in two-step mechanism. Step 1 is an electrophilic addition step, in which the pair of electrons from the electron-rich $\text{π}$ bond forms a bond to the acid’s electron-poor atom. One of the originally double-bonded carbon atoms develops a +1 formal charge, making it a carbocation. Step 2 is a coordination step, whereby the halide forms a bond to the carbocation. In an electrophilic addition of a Bronsted acid to an alkene, the rate-determining step is Step $\text{1}$, the addition of the ${\text{H}}^{\text{+}}$ electrophile. It is identical to the second step of the ${\text{S}}_{\text{N}}\text{1}$ reaction mechanism.

Answer to Problem 11.1P

The complete mechanism of the given addition reaction is

The major product of the reaction is

Explanation of Solution

The given addition reaction is

The given reaction occurs in two steps. The electrophilic addition is the first elementary step. The $\text{π}$ electrons of the C=C act as the electron-rich species, and the H atom of the ${\text{H-OSO}}_{\text{3}}\text{H}$ of the acid acts as the electron-poor species (electrophile). A carbocation forms in the first step. The second elementary step is one of coordination, where the conjugate base ${}^{-}{\text{OSO}}_{\text{3}}\text{H}$ acts as the nucleophile and adds to the carbocation.

Conclusion

The product of an electrophilic addition reaction is formed as a result of the addition of the two parts of a Bronsted acid across a double bond, replacing one $\text{π}$ bond with two $\text{σ}$ bonds.

Interpretation Introduction

(d)

Interpretation:

For the given reaction, the complete, detailed mechanism is to be drawn, and the major product is to be predicted.

Concept introduction:

An electrophilic addition reaction is an addition reaction where a $\text{π}$ bond is broken and two new $\text{σ}$ bonds are formed. This reaction occurs in two-step mechanism. Step 1 is an electrophilic addition step, in which the pair of electrons from the electron-rich $\text{π}$ bond forms a bond to the acid’s electron-poor atom. One of the originally double-bonded carbon atoms develops a +1 formal charge, making it a carbocation. Step 2 is a coordination step, whereby the halide forms a bond to the carbocation. In an electrophilic addition of a Bronsted acid to an alkene, the rate-determining step is Step $\text{1}$, the addition of the ${\text{H}}^{\text{+}}$ electrophile. It is identical to the second step of the ${\text{S}}_{\text{N}}\text{1}$ reaction mechanism.

Answer to Problem 11.1P

The complete mechanism of the given addition reaction is

The major product of the reaction is

Explanation of Solution

The given addition reaction is

The given reaction occurs in two steps. The electrophilic addition is the first elementary step. The $\text{π}$ electrons of the C=C act as the electron-rich species, and the H atom of the acid HBr acts as the electron-poor species (electrophile). A carbocation forms in the first step. The second elementary step is one of coordination, where the conjugate base ${\text{Br}}^{-}$ acts as the nucleophile and adds to the carbocation.

Conclusion

The product of an electrophilic addition reaction is formed as a result of the addition of the two parts of a Bronsted acid across a double bond, replacing one $\text{π}$ bond with two $\text{σ}$ bonds.