Question

Methyl vinyl ketone on reaction with ${\text{LiCuM}}{{\text{e}}_{\text{2}}}$ ​gives a major product, whose structure is:
A.

         ![](https://www.vedantu.com/question-sets/f894da2d-e8a4-42b6-af7f-7f257b4e9a537253384830347496603.png)

B.

                        ![](https://www.vedantu.com/question-sets/f395c76a-d522-48d7-a028-9c83664749b52695127951445090058.png)   

C.

                   ![](https://www.vedantu.com/question-sets/38a63000-fbeb-43d0-8d75-2709c52841325822292173932031270.png)  

D.

Answer 1

When methyl vinyl ketone (Butenone) react with Lithium dimethyl copper (diorganocopper), and during this reaction methylation occur (addition of methyl group to the compound) and it produces a compound with ketone group i.e. Pentan-2-one.

Complete step by step answer:
Butenone is IUPAC name for Methyl vinyl ketone which is an organic compound having molecular formula $C{H_3}C\left( O \right)CH = C{H_2}$. This compound classified under an enone and is very reactive. It is colourless in appearance, flammable in nature with pungent odour and is highly toxic. It shows high affinity towards solvents and pure water and acts as an important intermediate in the formation of other compounds.
A lithium copper (diorganocopper) reagent compound is a Gilman reagent. ${R_2}CuLi$ where $R$is an alkyl or aryl. These reagents are more useful because, unlike other related Grignard reagents and organolithium reagents, these reagent reacts with organic halides to replace the halide group with a $R$ group (the Corey–House reaction). Such displacement reactions help for the production of complex products from simple building blocks.
These reagents were discovered by Henry Gilman and his team. Lithium dimethyl copper ${\left( {C{H_3}} \right)_2}CuLi$ can be prepared by addition of copper (I) iodide to methyl lithium in tetrahydrofuran at$- 78\;^\circ C$. In the following reaction the Gilman reagent is a methylating reagent reacting with an alkyne as a conjugate addition, and the negative charge gets trapped in a nucleophilic acyl substitution with the ester group producing a cyclic enone.
In the given question, the following reaction happens

Thus, option A is the correct answer.

Note: Methyl vinyl ketone is extremely hazardous for human beings, once inhaled it causes coughing, wheezing and shortness of breath even at very low concentrations. It also results in irritation of the skin, eyes, and other respiratory membranes.