Why strong acid and high temp for E1 reaction?

[zoner]

I never learned this before and TBR doesn't explain why...

Thanks in advance.

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[bkprodigy]

I never learned this before and TBR doesn't explain why...

Thanks in advance.

Strong acid protonates the leaving group, making it even better leaving group. Higher temp scews the rxn toward E1 from S1.

 

[zoner]

but protonation could also lead to SN1 making the leaving group easier to leave

 

[justhanging]

but protonation could also lead to SN1 making the leaving group easier to leave

Two quick rule of thumbs about Sub and elim. reactions. Wen you have SN1 there is ALWAYS E1. More heat or energy always favors elimination reactions over substitution reactions because of entropy reasons. Your right that protonation in both leads to better leaving groups.

 

[zoner]

Two quick rule of thumbs about Sub and elim. reactions. Wen you have SN1 there is ALWAYS E1. More heat or energy always favors elimination reactions over substitution reactions because of entropy reasons. Your right that protonation in both leads to better leaving groups.

but what if you had answer choices where it said

a) temp and pH both low
b) temp high and pH low

E1? or SN1?

 

[justhanging]

but what if you had answer choices where it said

a) temp and pH both low
b) temp high and pH low

E1? or SN1?

For high temp, E1 for sure. For low temp am not sure. If you think about it the first step of both of those reactions would be the same, protonation and water leaving forming a carbocation. The difference comes in what the nucleophile does. If it behaves as a base than its elimination otherwise substitution. My best take would be that at low temperatures you would have both reactions competing.

 

[zoner]

ok, the answer was E1 though

 

[BerkReviewTeach]

ok, the answer was E1 though

Which question are you talking about exactly, because as mentioned above (great insights BTW), there are a couple details about the presence of a nucleophile that will influence your answer.

I want to jump in, but I've been through every passage in orgo book 1 and can't find the exact answer choices you've listed. There are some passages that have corresponding tables, which is what you should be using to determine whether it went by E1 or SN1. Those passages are trying to emphasize using the data they give you to determine what transpired.

Is it something like that?

 

[lolarogers]

A single reactant undergoes reorganization of its chemical bonds, producing an isomer of the reactant.