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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: JoeyBob on December 03, 2019, 09:38:20 PM

Title: E1 reaction on primary halides
Post by: JoeyBob on December 03, 2019, 09:38:20 PM

Was wondering if E1 reactions occur on primary halides if the resulting carbocation can be rearranged to a tertiary position.

Neopentyl, for instance, undergoes E1 despite a primary halide being present.

Title: Re: E1 reaction on primary halides
Post by: spirochete on December 03, 2019, 11:32:25 PM

Yes, although it is thought that the rearrangement happens concerted with the methyl shift. Neopentyl can also do Sn2 in cases that strongly favor Sn2 over ionization, such as PBr3 in aprotic solvent.

Title: Re: E1 reaction on primary halides
Post by: JoeyBob on December 04, 2019, 04:53:08 PM

Quote from: spirochete on December 03, 2019, 11:32:25 PM

Yes, although it is thought that the rearrangement happens concerted with the methyl shift. Neopentyl can also do Sn2 in cases that strongly favor Sn2 over ionization, such as PBr3 in aprotic solvent.

Really? Because our textbook claims that neopentyl doesn't actually go through Sn2 reactions because of steric hindrance. With its rate being 10^-5 (so essentially 0) for Sn2 compared to 30 for a methyl halide.