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Question: What is Z in the following reaction? \(BC{l_3} + {H_2}\xrightarrow[{450}]{{Cu,Al}}X + HCl\) \(X\...

What is Z in the following reaction?
BCl3+H2→450Cu,AlX+HClBC{l_3} + {H_2}\xrightarrow[{450}]{{Cu,Al}}X + HCl
X→MethylationZX\xrightarrow{{Methylation}}Z
A. (CH3)BH2(C{H_3})B{H_2}
B. (CH3)4B2H2{(C{H_3})_4}{B_2}{H_2}
C. (CH3)3B2H3{(C{H_3})_3}{B_2}{H_3}
D. (CH3)6B2{(C{H_3})_6}{B_2}

Explanation

Solution

A process which either involves the addition of a methyl group in a substrate or substitution of an atom or a group by the methyl group is called methylation, while the removal or detachment of the methyl group from a compound is called demethylation. The process of methylation can be either electrophilic or nucleophilic depending upon the source of the methyl group.

Complete answer:
Boron trichloride is when treated with hydrogen in presence of copper and aluminum at low pressure and hence subjected to silent electric discharge results in the formation of diborane, a chemical compound that is composed of boron and hydrogen with chemical formula B2H6. Therefore, the compound X is diborane.
BCl3+H2→Cu,AlB2H6+HClBC{l_3} + {H_2}\xrightarrow{{Cu,Al}}{B_2}{H_6} + HCl
Now, according to the question when diborane is subjected to methylation which leads to the formation of the chemical compound Z. Diborane consists of two types of bond with hydrogen i.e. four-terminal B-H bond and two bridged B-H-B bonds. So, during methylation, all the four-terminal hydrogen atoms are replaced with methyl group leading to the formation of tetramethyl diborane with chemical formula (CH3)4B2H2{(C{H_3})_4}{B_2}{H_2}. Therefore, the compound Z formed by the methylation of compound X which was diborane is tetramethyl diborane.
B2H6→Methylation(CH3)4B2H2{B_2}{H_6}\xrightarrow{{Methylation}}{(C{H_3})_4}{B_2}{H_2}
So the correct answer is option B.

Note:
Diborane consists of four hydrides as its terminal and two bridges between the boron centres. Diborane can be prepared either by the reaction of iodine with sodium borohydride in presence of diglyme or by heating magnesium boride with hydrogen chloride, which results in the formation of a mixture of volatile diborane. Diborane is a common rocket propellant.