Are you saying this reaction will only undergo SN1?
Why wouldn't Br- (weak base) with tertiary substrate be able to undergo E1?
Can you clarify your explanation?
My thoughts are that it is a tertiary substrate.
It won't go SN2 since there is no strong Nucleophile and substrate is too hindered. It won't go E2 because we don't have a strong base.
The only options left are SN1 & E1
Tertiary substrate + Br- (weak base) = E1 (Cis/trans Alkene product)
In SN1, strength of nucleophile is not important. Only substrate is important and the solvent. Although a weak nucleophile will favor SN1. In this case our substrate is favorable to SN1 rxn (racemic products).
okay ppl, "
A base cannot go under substitution reaction."
I was just trying to explain the difference b/w a base and a nu here. I explained this previously, simply scroll up a little!
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To RSD2014,
"My thoughts are that it is a tertiary substrate.
It won't go SN2 since there is no strong Nucleophile and substrate is too hindered. It won't go E2 because we don't have a strong base.
The
only options left are SN1 & E1"
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My comment: You are absolutely right till here. and this is the best way to eliminate wrong answer choices.
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"Tertiary substrate + Br- (weak base) = E1 (Cis/trans Alkene product)
In SN1, strength of nucleophile is not important. Only substrate is important and the solvent. Although a weak nucleophile will favor SN1. In this case our substrate is favorable to SN1 rxn (racemic products)."
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My comment: The better way to ask the question is:
tertiary substrate + Br- (weak base/moderate nucleophile) = E1 (b/c of the weak base) and Sn1 (b/c of the moderate nucleophile)
then why do we get Sn1 as a major reaction here and not E1?
we should not forget that Br- is a moderate nucleophile and a very weak base (cause HBr is one of the strongest acids, and it's conjugate base Br- is a very weak base). And yes, sn1 does not depend on the strength of nucleophiles. But most importantly, Br- is quite stable as a base. Instead of accepting a proton like a base, it'll tend to attack the electrophilic carbon like a nucleophile, and that way Substitution wins over Elimination.
weak base but strong nucleophile (e.g. CN-) with a tertiary carbon substrate will also undergo Sn1 and not E1.
I can't remember of any weak base that is also a strong nucleophile reacting with a tertiary carbon that could undergo both E1 and Sn1. [ROH is both weak base and weak nucleophile, so it CAN undergo both E1 and Sn1 if it reacts with a tertiary carbon substrate, but then we'll have to look at the solvent]
Like I mentioned before, F-, Cl-, Br-, I-, CN-, RS-, RSH nucleophiles do not act as base. [reference: o.chem as a second language, pg#259]. These are moderate to strong nucleophiles and very weak bases, but they do not "act" as base and accept proton. Instead they act as nice nucleophiles and attack the tertiary carbon.
lol jk.
