# What are alkyl substituents?

${C}_{n} {H}_{2 n + 1}$ residues.
The general formula for all alkanes is ${C}_{n} {H}_{2 n + 2}$. This formula describes ALL alkanes, and we say the molecule is $\text{saturated}$, that is $C - H$ are at a maximum. Each time we substitute the carbon chain with another functional group, we replace 1 hydrogen with that functional group; cf. $C {H}_{4}$ versus $C {H}_{3} X$, $2 n + 1$ as req'd........