Nucleophilic reactions halides, lithium cuprate

A key step in the reaction mechanism appears to be nucleophilic attack on the alkyl halide by the negatively charged copper atom but the details of the mechanism are not well understood Indeed there is probably more than one mechanism by which cuprates react with organic halogen compounds Vinyl halides and aryl halides are known to be very unreactive toward nucleophilic attack yet react with lithium dialkylcuprates... 

Answer We are starting with an acid halide. So, in order to predict the major product of this reaction, we will have to determine if the nucleophile attacks once or twice. The reagent is a lithium diaUcyl cuprate. This reagent is a carbon nucleophile, but it is not like a Grignard reagent—it does not attack twice. Instead, it will only attack once, because it is a very tame carbon nucleophile, as we saw earlier in this section. And the product is expected to be a ketone ... 

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