Which reagent?

[ziggy1104]

In O-chem odyssey, one of the questions is asking which reagent would be best for a particular elimination rxn. I was going to post a picture of the question, but I know Dr. Jim is strict about copyright laws. Since you obviously can't see the reaction, can anyone just give me a basic rundown of how I can figure out which reagent would work best for either an E2 or E1 rxn? Thanks

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[matty675]

For E2 you need a strong base (-OR, -OH, etc.) which will most often be in a polar aprotic solvent. A strong base can be different from a strong Nu- in some cases so be careful when deciding whether SN2 or E2 will occur. SN2 does not require a strong base, but rather a strong Nu-. The Electrophile favorability is 3>2>1 for E2 reactions. You cannot limit a reaction to only E1. SN1 will always compete with E1 and therefore the best reagents for E1 are the same as for SN1- weak base/Nu- in a polar protic solvent. Common reagents include water and alcohols. Often times the solvent acts as the base/Nu- in these reactions

 

[ziggy1104]

Thank you!!