Catalytic hydrogenation is a best way to convert unsaturated hydrocarbons alkenes & alkynes into alkanes. Reactants passed over surface of the metals like Pd, Pt, Ni and a transition state develops between the reactants from same side and that is why it is a syn addition. Mechanism in case of other metals H2 molecule will be adsorbed on the surface of metal Imp. To compare rate : (i) More the stable alkene less will be the rate of hydrogenation. (ii) Steric hindrance will decrease the rate of hydrogenation. If Pd / BaSO4 is used alkenes are not reduced to alkanes and major product of alkyne reduction is cis alkene.

Catalytic hydrogenation is a best way to convert unsaturated hydrocarbons alkenes & alkynes into alkanes. Reactants passed over surface of the metals like Pd, Pt, Ni and a transition state develops between the reactants from same side and that is why it is a syn addition.

Mechanism in case of other metals H₂ molecule will be adsorbed on the surface of metal

Imp. To compare rate :
(i) More the stable alkene less will be the rate of hydrogenation.
(ii) Steric hindrance will decrease the rate of hydrogenation.
If Pd / BaSO₄ is used alkenes are not reduced to alkanes and major product of alkyne reduction is cis alkene.

Linked Question 1

Select correct statement :

None of these

C is optically active

B is optically active

A is optically inactive

Linked Question 2

How many alkene on catalytic hydrogenation give iso-pentane as a product.

Linked Question 3

Select incorrect statement :

All isomers of the formula C₅H₁₂ can be prepared by catalytic hydrogenation of alkene

All isomers of the formula C₆H₁₄ can be prepared by catalytic hydrogenation of alkene

Methane cannot be prepared by catalytic hydrogenation of alkene

Methane can not prepared by catalytic hydrogenation of alkene
${CH}_{3} - {CH}_{2} - {CH}_{2} - {CH}_{2} - CH = C H_{2} \underset{Ni}{\overset{H_{2}}{\to}} {CH}_{3} - {CH}_{2} - {CH}_{2} - {CH}_{2} - {CH}_{2} - {CH}_{3}$