Chapter 7, Problem 45P

(a)

Interpretation Introduction

Interpretation: The major organic products that would result from the reaction of $\text{1-bromobutane}$ with $\text{KCl}$ in DMF along with the dominant pathway adopted among $\text{E1}$ , $\text{E}2$ , ${\text{S}}_{\text{N}}1$ or ${\text{S}}_{\text{N}}2$ should be predicted.

Concept introduction: Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene. Stronger the base more is the probability of elimination over substitution over elimination. Further, if the still higher concentration is employed reaction proceeds via bimolecular elimination. On the other hand, the weak base waits until the carbocation is formed and the type of elimination with a relatively weak base is two-step elimination or $\text{E1}$ .

Three principal factors that affect the competition between substitution and elimination: basicity of the nucleophile, steric hindrance in the alkyl halide, and steric bulk around the nucleophilic atom. The bases such as hydroxide ion, alkoxide ion, amide ion, tertiary amines are highly strong bases that favor elimination over substitution. On the other hand bases such as methanol, halides, alkyl phosphines, azides, cyanides, acetates are regarded as weak bases and they form substitution products in greater ratios than elimination products.

Analogous to the case that strong nucleophiles are more favored to react via ${\text{S}}_{\text{N}}2$ the pathway, the greater concentration of strong bases are more favored for single-step elimination $\text{E}2$ pathway. Such strong bases include hydroxide ion or alkoxide ions. The reason of predominance of $\text{E}2$ elimination is that strong bases have high probabilities and high rates to abstract hydrogen from carbon adjacent to the carbocation.

(b)

Interpretation Introduction

Interpretation: The major organic products that would result from the reaction of $\text{1-bromobutane}$ with $\text{KI}$ in DMF along with the dominant pathway adopted among $\text{E1}$ , $\text{E}2$ , ${\text{S}}_{\text{N}}1$ or ${\text{S}}_{\text{N}}2$ should be predicted.

Concept introduction: Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene. Stronger the base more is the probability of elimination over substitution over elimination. Further, if the still higher concentration is employed reaction proceeds via bimolecular elimination. On the other hand, the weak base waits until the carbocation is formed and the type of elimination with a relatively weak base is two-step elimination or $\text{E1}$ .

Analogous to the case that strong nucleophiles are more favored to react via ${\text{S}}_{\text{N}}2$ the pathway, the greater concentration of strong bases are more favored for single-step elimination $\text{E}2$ pathway. Such strong bases include hydroxide ion or alkoxide ions. The reason of predominance of $\text{E}2$ elimination is that strong bases have high probabilities and high rates to abstract hydrogen from carbon adjacent to the carbocation.

(c)

Interpretation Introduction

Interpretation: The major organic products that would result from the reaction of $\text{1-bromobutane}$ with $\text{KCl}$ in ${\text{CH}}_{\text{3}}{\text{NO}}_{\text{2}}$ along with the dominant pathway adopted among $\text{E1}$ , $\text{E}2$ , ${\text{S}}_{\text{N}}1$ or ${\text{S}}_{\text{N}}2$ should be predicted.

Concept introduction: Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene. Stronger the base more is the probability of elimination over substitution over elimination. Further, if the still higher concentration is employed reaction proceeds via bimolecular elimination. On the other hand, the weak base waits until the carbocation is formed and the type of elimination with a relatively weak base is two-step elimination or $\text{E1}$ .

Analogous to the case that strong nucleophiles are more favored to react via ${\text{S}}_{\text{N}}2$ the pathway, the greater concentration of strong bases are more favored for single-step elimination $\text{E}2$ pathway. Such strong bases include hydroxide ion or alkoxide ions. The reason of predominance of $\text{E}2$ elimination is that strong bases have high probabilities and high rates to abstract hydrogen from carbon adjacent to the carbocation.

(d)

Interpretation Introduction

Interpretation: The major organic products that would result from the reaction of $\text{1-bromobutane}$ with ammonia and ethanol along with the dominant pathway adopted among $\text{E1}$ , $\text{E}2$ , ${\text{S}}_{\text{N}}1$ or ${\text{S}}_{\text{N}}2$ should be predicted.

Concept introduction: Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene. Stronger the base more is the probability of elimination over substitution over elimination. Further, if the still higher concentration is employed reaction proceeds via bimolecular elimination. On the other hand, the weak base waits until the carbocation is formed and the type of elimination with a relatively weak base is two-step elimination or $\text{E1}$ .

Analogous to the case that strong nucleophiles are more favored to react via ${\text{S}}_{\text{N}}2$ the pathway, the greater concentration of strong bases are more favored for single-step elimination $\text{E}2$ pathway. Such strong bases include hydroxide ion or alkoxide ions. The reason of predominance of $\text{E}2$ elimination is that strong bases have high probabilities and high rates to abstract hydrogen from carbon adjacent to the carbocation.

(e)

Interpretation Introduction

Interpretation: The major organic products that would result from the reaction of $\text{1-bromobutane}$ with ${\text{NaOCH}}_2{\text{CH}}_{\text{3}}$ in ${\text{CH}}_{\text{3}}{\text{CH}}_2\text{OH}$ along with the dominant pathway adopted among $\text{E1}$ , $\text{E}2$ , ${\text{S}}_{\text{N}}1$ or ${\text{S}}_{\text{N}}2$ should be predicted.

Concept introduction: Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene. Stronger the base more is the probability of elimination over substitution over elimination. Further, if the still higher concentration is employed reaction proceeds via bimolecular elimination. On the other hand, the weak base waits until the carbocation is formed and the type of elimination with a relatively weak base is two-step elimination or $\text{E1}$ .

Analogous to the case that strong nucleophiles are more favored to react via ${\text{S}}_{\text{N}}2$ the pathway, the greater concentration of strong bases are more favored for single-step elimination $\text{E}2$ pathway. Such strong bases include hydroxide ion or alkoxide ions. The reason of predominance of $\text{E}2$ elimination is that strong bases have high probabilities and high rates to abstract hydrogen from carbon adjacent to the carbocation.

(f)

Interpretation Introduction

Interpretation: The major organic products that would result from the reaction of $\text{1-bromobutane}$ in ${\text{CH}}_{\text{3}}{\text{CH}}_2\text{OH}$ along with the dominant pathway adopted among $\text{E1}$ , $\text{E}2$ , ${\text{S}}_{\text{N}}1$ or ${\text{S}}_{\text{N}}2$ should be predicted.

Concept introduction: Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene. Stronger the base more is the probability of elimination over substitution over elimination. Further, if the still higher concentration is employed reaction proceeds via bimolecular elimination. On the other hand, the weak base waits until the carbocation is formed and the type of elimination with a relatively weak base is two-step elimination or $\text{E1}$ .

Analogous to the case that strong nucleophiles are more favored to react via ${\text{S}}_{\text{N}}2$ the pathway, the greater concentration of strong bases are more favored for single-step elimination $\text{E}2$ pathway. Such strong bases include hydroxide ion or alkoxide ions. The reason of predominance of $\text{E}2$ elimination is that strong bases have high probabilities and high rates to abstract hydrogen from carbon adjacent to the carbocation.

(g)

Interpretation Introduction

Interpretation: The major organic products that would result from the reaction of $\text{1-bromobutane}$ in ${\text{CH}}_{\text{3}}{\text{CH}}_2\text{OH}$ along with the dominant pathway adopted among $\text{E1}$ , $\text{E}2$ , ${\text{S}}_{\text{N}}1$ or ${\text{S}}_{\text{N}}2$ should be predicted.

Concept introduction: Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene. Stronger the base more is the probability of elimination over substitution over elimination. Further, if the still higher concentration is employed reaction proceeds via bimolecular elimination. On the other hand, the weak base waits until the carbocation is formed and the type of elimination with a relatively weak base is two-step elimination or $\text{E1}$ .

Analogous to the case that strong nucleophiles are more favored to react via ${\text{S}}_{\text{N}}2$ the pathway, the greater concentration of strong bases are more favored for single-step elimination $\text{E}2$ pathway. Such strong bases include hydroxide ion or alkoxide ions. The reason of predominance of $\text{E}2$ elimination is that strong bases have high probabilities and high rates to abstract hydrogen from carbon adjacent to the carbocation.

(h)

Interpretation Introduction

Interpretation: The major organic products that would result from the reaction of $\text{1-bromobutane}$ with ${\left({\text{CH}}_{\text{3}}\right)}_3\text{P}$ in ${\text{CH}}_{\text{3}}\text{OH}$ along with the dominant pathway adopted among $\text{E1}$ , $\text{E}2$ , ${\text{S}}_{\text{N}}1$ or ${\text{S}}_{\text{N}}2$ should be predicted.

Concept introduction: Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene. Stronger the base more is the probability of elimination over substitution over elimination. Further, if the still higher concentration is employed reaction proceeds via bimolecular elimination. On the other hand, the weak base waits until the carbocation is formed and the type of elimination with a relatively weak base is two-step elimination or $\text{E1}$ .

Analogous to the case that strong nucleophiles are more favored to react via ${\text{S}}_{\text{N}}2$ the pathway, the greater concentration of strong bases are more favored for single-step elimination $\text{E}2$ pathway. Such strong bases include hydroxide ion or alkoxide ions. The reason of predominance of $\text{E}2$ elimination is that strong bases have high probabilities and high rates to abstract hydrogen from carbon adjacent to the carbocation.

(i)

Interpretation Introduction

Interpretation: The major organic products that would result from the reaction of $\text{1-bromobutane}$ in ${\text{CH}}_{\text{3}}\text{COOH}$ along with the dominant pathway adopted among $\text{E1}$ , $\text{E}2$ , ${\text{S}}_{\text{N}}1$ or ${\text{S}}_{\text{N}}2$ should be predicted.

Concept introduction: Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene. Stronger the base more is the probability of elimination over substitution over elimination. Further, if the still higher concentration is employed reaction proceeds via bimolecular elimination. On the other hand, the weak base waits until the carbocation is formed and the type of elimination with a relatively weak base is two-step elimination or $\text{E1}$ .

Analogous to the case that strong nucleophiles are more favored to react via ${\text{S}}_{\text{N}}2$ the pathway, the greater concentration of strong bases are more favored for single-step elimination $\text{E}2$ pathway. Such strong bases include hydroxide ion or alkoxide ions. The reason forthe predominance of $\text{E}2$ elimination is that strong bases have high probabilities and high rates to abstract hydrogen from carbon adjacent to the carbocation.