Question

Question #a1805

Answer 1

Your premise is incorrect. Substitution and hydrogenation do not both involve the removal of hydrogen atoms from alkanes.

Substitution

Substitution in an alkane involves the removal of a hydrogen atom and its replacement with something else.

An example is the chlorination of methane.

H₃C-H + Cl-Cl → H₃C-Cl + H-Cl

Hydrogenation

Alkanes do not undergo hydrogenation. Hydrogenation is the addition of hydrogen to an alkene.

Hydrogenation does not remove H atoms from the alkene. Instead, it adds H atoms to the alkene.

An example is the hydrogenation of ethene.

H₂C=CH₂ + H-H → H-CH₂-CH₂-H