Difference Between SN2 and Addition Elimination.

[MedicalMan14]

Can anyone explain this to me and how I was to tell the difference if an MCAT question asked "Is this Addition Elimination or Substitution?".

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[bxadook]

Nucleophillic addition-elimination occurs whenever you have carbonyl compound with a good leaving group attached at the alpha position to the carbonyl carbon.

An SN2 reaction occurs mainly on primary alkyl halides in which the nucleophile attacks from the opposite side of the leaving group. A 5-bond transition state (thank you joshto) is formed, and degrades immediately donating a pair of electrons to the leaving group.

 

[MedicalMan14]

Thank you for the clarification!!

 

[joshto]

A 5-bond intermediate is formed, and degrades immediately donating a pair of electrons to the leaving group.

SN2 reactions do NOT have intermediates. they have transition states.

 

[NuttyEngDude]

Do addition-elimination reactions only occur in carboxylic acid and derivatives? ie. where there is a double bond oxygen that becomes a positively charged water molecule that wants to leave?

edit: i am not expecting the original people in this thread to respond, but replying so as to not just make new threads 😛