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A Gilman reagent refers to the copper and lithium reagent containing two R groups (alkyl or aryl). It is a type of organometallic reagent, expressed as R₂CuLi. Unlike Grignard reagents, when reacted with organic halides, these compounds replace the halide group with an R group.

The most common example of Gilman reagent is lithium dimethylcuprate.

(CH₃)₂ CuLi

Bromination is the chemical reaction involving the reaction of a compound, and bromine results in bromine being added to the compound.The new product formed has different properties than the initial one.

(a) The initial reaction of methanol with PBr₃ in the presence of catalyst pyridine turns the OH into a good leaving group, which is then expelled out by bromine in the S_N2 reaction to produce methyl bromide. It is then treated with Li in the presence of CuI, producing lithium dimethylcuprate (Gilman reagent), which undergoes a reaction with formaldehyde (HCHO) in the presence of acid HCl to produce ethanol.

The complete reaction with all the reagents is shown below.

Reaction (a)

(b) The initial reaction of methane molecule on treatment with Br₂ in the presence of sunlight produce bromomethane. This is a substitution reaction because one of the hydrogen atoms of methane is replaced by a bromine atom in the mixture.

It is then treated with Li in the presence of CuI, producing lithium dimethylcuprate (Gilman reagent), which undergoes a reaction with ethylene dioxide in the presence of acid HCl to produce propanol, which is our final product of the reaction.

The complete reaction with all the reagents is shown below.

Reaction (b)