Chapter 6, Problem 6.30SP

(a)

Interpretation Introduction

To determine: The method of conversion of $1$-phenylpropane to $1$-bromo-$1$-phenylpropane and unwanted products that might produce undesirable impurities in the product.

Interpretation: The method of conversion of $1$-phenylpropane to $1$-bromo-$1$-phenylpropane and unwanted products that might produce undesirable impurities in the product is to be stated.

Concept introduction: NBS is N-bromosuccinimide. It is used as an alternative for ${\text{Br}}_{\text{2}}$. The chemical reaction involved in the replacement of an allylic carbon by bromine is known as allylic bromination. NBS provides low concentration of ${\text{Br}}_{\text{2}}$.

Answer to Problem 6.30SP

The conversion of $1$-phenylpropane to $1$-bromo-$1$-phenylpropane is shown in Figure 1.

Explanation of Solution

The conversion of $1$-phenylpropane to $1$-bromo-$1$-phenylpropane is shown below.

Figure 1

In the above reaction, $1$-phenylpropane reacts with NBS to form $1$-bromo-$1$-phenylpropane, NBS is N-bromosuccinimide. In benzylic bromination, it acts as bromine source. Benzylic position is next to aromatic ring. NBS provides a consistently low concentration of ${\text{Br}}_{\text{2}}$ which is essential to avoid undesirable products. If concentration of bromine is high, then it will add to the double bonds of aromatic ring to form unwanted products.

(b)

Interpretation Introduction

To determine: The method of conversion of $1$-phenylpropane to $1$-methoxy-$1$-phenylpropane and unwanted products that might produce undesirable impurities in the product.

Interpretation: The method of conversion of $1$-phenylpropane to $1$-methoxy-$1$-phenylpropane and unwanted products that might produce undesirable impurities in the product is to be stated.

Concept introduction: NBS is N-bromosuccinimide. It is used as an alternative for ${\text{Br}}_{\text{2}}$. The chemical reaction involved in the replacement of an allylic carbon by bromine is known as allylic bromination. NBS provides low concentration of ${\text{Br}}_{\text{2}}$.

Answer to Problem 6.30SP

The conversion of $1$-phenylpropane to $1$-methoxy-$1$-phenylpropane is shown in Figure 2 and Figure 3.

Explanation of Solution

In first step, $1$-phenylpropane reacts with NBS to form $1$-bromo-$1$-phenylpropane as shown below. The mechanism will be predominantly second order (${\text{S}}_{\text{N}}\text{2}$).

Figure 2

In the second step, $1$-bromo-$1$-phenylpropane reacts with ethoxide ion to form $1$-methoxy-$1$-phenylpropane. The mechanism will be predominantly first order (${\text{S}}_{\text{N}}1$). $1$-bromo-$1$-phenylpropane is a secondary halide. Undesirable products are formed in ${\text{S}}_{\text{N}}1$ mechanism.

Figure 3

(c)

Interpretation Introduction

To determine: The method of conversion of $1$-phenylpropane to $2$-phenylbutanenitrile and unwanted products that might produce undesirable impurities in the product.

Interpretation: The method of conversion of $1$-phenylpropane to $2$-phenylbutanenitrile and unwanted products that might produce undesirable impurities in the product is to be stated.

Concept introduction: NBS is N-bromosuccinimide. It is used as an alternative for ${\text{Br}}_{\text{2}}$. The chemical reaction involved in the replacement of an allylic carbon by bromine is known as allylic bromination. NBS provides low concentration of ${\text{Br}}_{\text{2}}$.

Answer to Problem 6.30SP

The conversion of $1$-phenylpropane to $2$-phenylbutanenitrile is shown in Figure 2 and Figure 4.

Explanation of Solution

In first step, $1$-phenylpropane reacts with NBS to form $1$-bromo-$1$-phenylpropane as shown below. The mechanism will be predominantly second order (${\text{S}}_{\text{N}}\text{2}$).

In the second step, $1$-bromo-$1$-phenylpropane reacts with potassium cyanide to form $2$-phenylbutanenitrile. The mechanism will be predominantly first order (${\text{S}}_{\text{N}}1$). $1$-bromo-$1$-phenylpropane is a secondary halide. Undesirable products are formed in ${\text{S}}_{\text{N}}1$ mechanism.

Figure 4