Question

Alkyl halides reacts with dialkyl copper reagent to give:
A) Alkanes
B) Alkenes
C) Alkenyl Halides
E) Alkyl copper halides

Answer 1

Hint: The method of a coupling of alkyl halides with dialkyl copper reagent is called the Corey-House synthesis reaction. It involves the coupling of alkyl halides to generate higher hydrocarbons.

Complete step by step answer: Organic reactions involve the chemical reaction of organic molecules. The basic type of organic reactions are addition reaction, elimination reaction, pericyclic reaction, rearrangement reaction, etc.
- The dialkyl copper reagent is also called as Gilman reagent. It is also shown \[{{\text{R}}_{\text{2}}}\text{CuLi}\]where R is an alkyl or aryl group.
- The Corey-house synthesis is an organic reaction which involves the reaction of dialkyl copper \[{{\text{R}}_{\text{2}}}\text{CuLi}\]with the alkyl halide $\text{(R }\!\!'\!\!\text{ X)}$to form a hydrocarbon and metal halide as the by-product. It is a coupling of alkyl halides with the organometallic compound. The general reaction is given as follows,
- Step1)The alkyl halide is treated with lithium to give alkyl lithium. The alkyl halide can be primary, secondary, or tertiary:
\[\text{R-X+2Li}\to \text{R-Li+LiX}\]
- Step 2) An alkyl lithium is treated with cuprous iodide$\text{CuI}$to form the Gilman reagent that is lithium dialkyl cuprates: 
\[\text{2RLi + CuI }\to \text{ L}{{\text{i}}^{\text{+}}}{{\left[ \text{R-Cu-R} \right]}^{\text{-}}}\text{ }\!\!~\!\!\text{ + LiI}\]
Where, \[\text{L}{{\text{i}}^{\text{+}}}{{\left[ \text{R-Cu-R} \right]}^{\text{-}}}\]or \[{{\text{R}}_{\text{2}}}\text{CuLi}\] is lithium dialkyl cuprates
-Step3) In the last step of Corey-house synthesis, the lithium dialkyl cuprates react with the alkyl halide $\text{(R }\!\!'\!\!\text{ X)}$to give the alkane
\[{{\text{R}}_{\text{2}}}\text{CuLi+R }\!\!'\!\!\text{ -X}\to \text{R-R }\!\!'\!\!\text{ +R-Cu+LiX}\]
In this reaction $\text{(R }\!\!'\!\!\text{ X)}$ can be primary, secondary, or tertiary halide.
Thus the Alkyl halides react with dialkyl copper reagents to give alkane.
Hence, (A) is the correct option.

Additional information:
Importance of Corey–house synthesis:
- Corey-house synthesis is a better method than the Wurtz reaction. Here alkyl halide and lithium dialkyl copper reacts to give higher alkane.
- This method is a better method than the Wurtz reaction. An alkyl halide and a lithium dialkyl copper are reacted to give a higher hydrocarbon.
For example,
\[\text{C}{{\text{H}}_{\text{3}}}\text{C}{{\text{H}}_{\text{2}}}\text{C}{{\text{H}}_{\text{2}}}\text{Br+(C}{{\text{H}}_{\text{3}}}{{\text{)}}_{\text{2}}}\text{CuLi}\to \text{C}{{\text{H}}_{\text{3}}}\text{C}{{\text{H}}_{\text{2}}}\text{C}{{\text{H}}_{\text{3}}}\text{+C}{{\text{H}}_{\text{3}}}\text{Cu+LiBr}\]
- One of the noticeable features of this reaction is that it is used for the preparation of symmetrical, unsymmetrical, straight, or branched alkane.
- To get the better yield, use primary alkyl halide and primary, secondary or tertiary lithium dialkyl copper.

Note: For better yield the $\text{(R }\!\!'\!\!\text{ X)}$ must be methyl halide, benzyl halide, primary alkyl halide, or secondary cycloalkyl halide. That is if the $\text{(R }\!\!'\!\!\text{ X)}$is ${{3}^{0}}$ then due to steric hindrance the reaction may result in by-product and alkane becomes a minor product. It is useful for the synthesis of alkane with an odd number of carbon atoms that are difficult to be obtained from the Wurtz reaction.