Question

For which mechanisms — sn1, sn2, e1, or e2 — is the mechanism concerted? Select all that apply.

1) sn1
2) sn2
3) e1
4) e2

Answer 1

The SN2 and E2 mechanisms are concerted processes without any intermediates, while SN1 and E1 are not concerted as they involve the formation of a carbocation intermediate. The choice of mechanism is influenced by factors like solvent, nucleophile strength, steric hindrance, and the stability of potential intermediates.

Therefore , 2) and 3) are correct .

Step-by-step explanation:

In the context of organic reaction mechanisms, SN2 (bimolecular nucleophilic substitution) and E2 (bimolecular elimination) mechanisms are concerted processes. This means that all bonds are broken and formed in a single step without any intermediate.

On the other hand, SN1 (unimolecular nucleophilic substitution) and E1 (unimolecular elimination) mechanisms are not concerted. In these mechanisms, a carbocation intermediate is formed during the first, rate-determining step.

The solvent and the structure of the substrate are key factors in determining whether a reaction will follow an SN1, SN2, E1, or E2 mechanism. Strong bases and less steric hindrance favor an E2 mechanism, while stable carbocations and good leaving groups make SN1 and E1 mechanisms more likely. Secondary and tertiary substrates are more prone to undergo SN1 and E1 reactions due to steric hindrance that prevents SN2 reactions.