Question

Predict the organic product(s) of the reaction of 2 -butene with each reagent. (a) \(\mathrm{H}_{2} \mathrm{O}\left(\mathrm{H}_{2} \mathrm{SO}_{4}\right)\) (b) \(\mathrm{Br}_{2}\) (c) \(\mathrm{Cl}_{2}\) (d) \(\mathrm{Br}_{2}\) in \(\mathrm{H}_{2} \mathrm{O}\) (e) \(\mathrm{HI}\) (f) \(\mathrm{Cl}_{2}\) in \(\mathrm{H}_{2} \mathrm{O}\) (g) \(\mathrm{Hg}(\mathrm{OAc})_{2}, \mathrm{H}_{2} \mathrm{O}\) (h) product (g) \(+\mathrm{NaBH}_{4}\)

Short answer

Question: Predict the organic product(s) of the reaction of 2-butene with the following reagents: (a) \(\mathrm{H}_{2} \mathrm{O}\left(\mathrm{H}_{2} \mathrm{SO}_{4}\right)\) (b) \(\mathrm{Br}_{2}\) (c) \(\mathrm{Cl}_{2}\) (d) \(\mathrm{Br}_{2}\) in \(\mathrm{H}_{2} \mathrm{O}\) (e) \(\mathrm{HI}\) (f) \(\mathrm{Cl}_{2}\) in \(\mathrm{H}_{2} \mathrm{O}\) (g) \(\mathrm{Hg}(\mathrm{OAc})_{2}, \mathrm{H}_{2} \mathrm{O}\) (h) Product (g) \(+\mathrm{NaBH}_{4}\) Answer: (a) 2-butanol: \(\text{CH}_{3}\text{CHCH}_{2}\text{CH}_{2}\text{OH}\) (b) 2,3-dibromobutane: \(\text{CH}_{3}\text{CHBrCHBrCH}_{3}\) (c) 2,3-dichlorobutane: \(\text{CH}_{3}\text{CHClCHClCH}_{3}\) (d) 2-bromo-2-butanol: \(\text{CH}_{3}\text{CHBrCH}_{2}\text{CH}_{2}\text{OH}\) (e) 2-iodobutane: \(\text{CH}_{3}\text{CHICH}_{2}\text{CH}_{3}\) (f) 2-chloro-2-butanol: \(\text{CH}_{3}\text{CHClCH}_{2}\text{CH}_{2}\text{OH}\) (g) Mercurinium ion intermediate: \(\text{CH}_{3}\text{CH}\left[ \text{CH}_{2}\text{CH}_{2}\text{HgOAc} \right]\) (h) 2-butanol: \(\text{CH}_{3}\text{CHCH}_{2}\text{CH}_{2}\text{OH\)

Step-by-step solution

Identify the reaction type

This reagent is an acid-catalyzed hydration, which converts alkenes to alcohols. Specifically, 2-butene will undergo an electrophilic addition reaction.

Write the product

The reaction will produce 2-butanol. The product is: (\text{CH}_{3}\text{CHCH}_{2}\text{CH}_{2}\text{OH}$) (b) Reaction with \(\mathrm{Br}_{2}\)

Identify the reaction type

This reagent is a halogenation of the double bond, resulting in the addition of bromine atoms across the double bond in a stereoselective and anti addition manner.

Write the product

The reaction will produce 2,3-dibromobutane. The product is: (\text{CH}_{3}\text{CHBrCHBrCH}_{3}$) (c) Reaction with \(\mathrm{Cl}_{2}\)

Identify the reaction type

This reagent is similar to the previous one, but with chlorine instead of bromine. It is a halogenation reaction involving electrophilic addition.

Write the product

The reaction will produce 2,3-dichlorobutane. The product is: (\text{CH}_{3}\text{CHClCHClCH}_{3}$) (d) Reaction with \(\mathrm{Br}_{2}\) in \(\mathrm{H}_{2} \mathrm{O}\)

Identify the reaction type

This reaction is a halohydrin formation, which results from electrophilic addition of bromine and water across the double bond.

Write the product

The reaction will produce 2-bromo-2-butanol. The product is: (\text{CH}_{3}\text{CHBrCH}_{2}\text{CH}_{2}\text{OH}$) (e) Reaction with \(\mathrm{HI}\)

Identify the reaction type

This reagent is a hydrogen halide, which will undergo an electrophilic addition reaction with the 2-butene.

Write the product

The reaction will produce 2-iodobutane. The product is: (\text{CH}_{3}\text{CHICH}_{2}\text{CH}_{3}$) (f) Reaction with \(\mathrm{Cl}_{2}\) in \(\mathrm{H}_{2} \mathrm{O}\)

Identify the reaction type

This reaction is a halohydrin formation, which results from electrophilic addition of chlorine and water across the double bond.

Write the product

The reaction will produce 2-chloro-2-butanol. The product is: (\text{CH}_{3}\text{CHClCH}_{2}\text{CH}_{2}\text{OH}$) (g) Reaction with \(\mathrm{Hg}(\mathrm{OAc})_{2}, \mathrm{H}_{2} \mathrm{O}\)

Identify the reaction type

This reagent is used in oxymercuration-demercuration reactions as the first step, which converts alkenes to alcohols. It is an electrophilic addition reaction.

Write the product

The reaction will produce a mercurinium ion intermediate. The intermediate product is: \left(\text{CH}_{3}\text{CH}\left[ \text{CH}_{2}\text{CH}_{2}\text{HgOAc} \right]\right) (h) Product (g) \(+\mathrm{NaBH}_{4}\)

Identify the reaction type

This reaction is the second step in the oxymercuration-demercuration reaction. Sodium borohydride (\(\mathrm{NaBH}_{4}\)) is the reducing agent that removes the mercury from the intermediate formed in step (g).

Write the product

The final product after the reduction is 2-butanol. The product is: (\text{CH}_{3}\text{CHCH}_{2}\text{CH}_{2}\text{OH$)