# Which mechanism would be followed by a certain reaction with good leaving group?

In my class test, I was asked this question:

Which mechanism would be followed by a certain reaction with good leaving group?

1. E1 reaction

2. E2 reaction

3. No reaction

4. both E1 and E2

I answered 4 because they both occur simultaneously the main difference comes in the amount of product formed by them. But, I was awarded with negative marks.

Can anyone please tell if I was wrong on my part or my teacher?

• One point is: Your comparison of E1, E2 and E1cb should equally consider if there is synchronicity (e.g., the approach of a base and leaving of an other group across a transition state) or one after the other (passing intermediates, e.g. a base deprotonates the substrate, the carbanion then expels an other group) to yield e.g., an alkene. Which is not the same as letting $\ce{X-}$ leave to generate an intermediate carbocation eventually loosing H to yield an uncharged alkene. Dec 13 '20 at 15:05
• the reaction can follow any pathway just the conitions make one case or the other more probable
– user99515
Dec 13 '20 at 17:34
• Yes there are reactions which possibly could proceed by more than one pathway, already because on occasion it may be easier to reject a suggested mechanism than to collect supporting experimental evidence. Thus the suggest that you add to your question the reaction in question, to set it in specific context to your question. Dec 13 '20 at 18:44
• Take note also of the temperature at which the reaction is allowed to move— E1 reactions usually perform under high temeperatures (based from my Org Chem class in first year). Dec 14 '20 at 10:53
• IMO this question is nonsensical because you can't generally make a strong statement on ideas in organic chemistry. There are no hard and fast rules. Dec 15 '20 at 3:53