Question

Choose the correct reagent required to carry out the transformation:

• A. $Zn+conc.HCl$
• B. $conc.H_{2}S{O}_4$
• C. $Li,then{H}_{2}O$
• D. $H_2/Pt$

Answer 1

Answer: (D)

$H_2/Pt$

Dihydrogen gas adds to alkenes and alkynes in the presence of finely divided catalysts like platinum, palladium or nickel to form alkanes. This process is called hydrogenation. These metals adsorb dihydrogen gas on their surfaces and activate the hydrogen – hydrogen bond. Platinum and palladium catalyse the reaction at room temperature but relatively higher temperature and pressure are required with nickel catalysts.

The given Compound will convert to alkane on hydrogenation with hydrogen gas and platinum as a catalyst.

Concentrated sulphuric acid is used for hydrolysis of alkenes and cannot be used in the above reaction.

$Zn/HCl$ is used in Clemmensen reduction to convert aldehydes or ketones to alkanes and cannot be used in the above reaction.