How do we know which factor is most important to evaluate whether a reaction will proceed through SN1/SN2/E1/E2?

Question

Lucy Alessi · Accepted Answer

I see this question has not been addressed for some time....so I will stick my neck out...

The point is that YOU DON'T KNOW. And for this we apply #"a posteriori"# reasoning, argument AFTER the fact, rather than #"a priori"# reasoning, argument BEFORE the fact. Chemistry is therefore an experimental science. You do the experiment, note the results, and THEN try to rationalize the results; i.e. to see if the rationale has any validity. When two organic molecules are mixed under different conditions, with different reagents, anything can happen, and in fact you are likely to get SEVERAL products. We perform the experiment first, so we can't really say for sure, but as a generalization, we might assume that bulkier electrophiles, like methyl and primary alkyl halides, would be more likely to undergo dissociative reactions while less sterically encumbered electrophiles would tend to undergo associative reactions.

Isabella Acosta · Answer

undefined The key factors to consider when determining whether a reaction will proceed through SN1, SN2, E1, or E2 mechanisms include the nature of the substrate, the strength of the nucleophile/base, the solvent, and the leaving group. Additionally, the steric hindrance around the reacting center and the stability of the carbocation intermediate (for SN1 and E1 reactions) also play significant roles in determining the reaction mechanism.