Question

Will a primary-substituted leaving group always follow an SN2 pathway?

Answer 1

In general, SN2 will predominate if there is a strong nucleophile and a primary substrate.

However, E2 will beat out SN2 if there is a strong base only as a reagent (e.g. `NaH`), or if there is a bulky base (e.g. `t"ButO"^-`).

In the latter case, the "nucleophile" is too bulky to attack from the back in the concerted way an SN2 takes place. So a Hofmann product will be produced for E2.

If the reagent is a weak base/nucleophile, no reaction will appreciably occur for the purposes of this question.

Chemistry is never this simple! "Always"...