Explaining C-H bond strengths

The increased substitution of an alkane will make the C-H bonds weaker and and make the molecule's corresponding radical more stable. C-H bonds are weakened by the steric strain between two atoms or alkyl groups that are attached to the same carbon atom. When C-H bond is broken, the release of the strain leads to lower bond dissociation energies. The variation in instabilities of C-H bonds in alkanes invokes repulsive forces between atoms attached to the same atom.