Key Terms

  • alkyl halide
  • allylic
  • carbanion
  • delocalized
  • Grignard reagent (RMgX)
  • organohalide
  • organometallic

Summary of Reactions 6

No stereochemistry is implied unless specifically indicated with wedged, solid, and dashed lines.

  1. Preparation of alkyl halides from Alcohols

Reaction with HX

The reaction of tertiary alcohol with HX in the presence of ether forms an alkyl halide. The reactivity of alcohols in decreasing order is tertiary, secondary, and primary.

 

 

 

Reaction of 1° and 2° alcohols with SOCl2

The reaction of secondary alcohol with thionyl chloride in the presence of pyridine forms alkyl chloride where the OH in the reactant is replaced by Cl in the product.

 

 

Reaction of 1° and 2° alcohols with PBr3

The reaction of secondary alcohol with phosphorus tribromide in the presence of ether forms an alkyl bromide where the OH in the reactant is replaced by Br in the product.

 

 

Reaction of 1° and 2° alcohols with HF–pyridine

The reaction of cyclohexanol with HF in the presence of pyridine forms fluorocyclohexane. Pyridine is shown as a six-membered aromatic ring containing five carbon atoms and one nitrogen.

 

 

 

2. Reactions of alkyl halides

Formation of Grignard (organomagnesium) reagents

The reaction of RX with magnesium in the presence of ether forms a Grignard reagent having formula R-Mg-X.

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