Because bromocyclohexane is a secondary alkyl halide, both...

Name: Problem 53, Chapter 15: Organic Chemistry
Uploaded: 2020-10-30T04:13:06-08:00
Duration: 3 min 32 s
Channel: Arun Bana
Description: Because bromocyclohexane is a secondary alkyl halide, both cyclohexanol and cyclohexene are formed when the alkyl halide reacts with hydroxide ion. Suggest a method to synthesize cyclohexanol from bromocyclohexane that forms little or no cyclohexene.

Because bromocyclohexane is a secondary alkyl halide, both cyclohexanol and cyclohexene are formed when the alkyl halide reacts with hydroxide ion. Suggest a method to synthesize cyclohexanol from bromocyclohexane that forms little or no cyclohexene.

Key Concepts

Reaction Mechanisms in Alkyl Halide Reactions

Secondary alkyl halides can react via multiple pathways when exposed to bases or nucleophiles. In one pathway, a nucleophilic substitution (SN1 or SN2) replaces the halide with a nucleophile to form a new bond, whereas in another, an elimination (E1 or E2) removes a proton adjacent to the carbon bearing the leaving group, resulting in alkene formation. The selectivity between these competing pathways depends on factors such as the nature of the substrate, the strength and sterics of the nucleophile or base, the solvent, and the temperature. Understanding these factors is crucial for designing a synthesis that favors substitution over elimination.

Organometallic Reagents (Grignard Reagents)

Grignard reagents are formed by reacting an alkyl halide with magnesium metal in an anhydrous ether solvent. These reagents are highly nucleophilic and allow for the formation of carbon–carbon and carbon–oxygen bonds when they react with electrophiles. In synthesizing alcohols, a Grignard reagent can be generated from an alkyl halide, then reacted with an oxygen source (such as O2 or a carbonyl compound), and finally quenched with acid to yield the corresponding alcohol. This method avoids the direct base-induced elimination that often accompanies the reaction of secondary alkyl halides with hydroxide ions.

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