hoffman vs zaitsev

[1800RAW]

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ok I just wanna get this cleared up

in chads videos he mentions several times that the only way to get appreciable hoffman product (assuming all other proper E2 conditions) is to use a bulky base on a substrate with a tertiary LG. He says that even if a bulky base is used on a substrate with a secondary LG, you will still get almost all zaitsev product.

However, in the destroyer, question #133 shows 2-chlorobutane undergoing E2 elimination w/ t-butoxide to get 1-butene, not 2-butene as chad said would occur.

So basically what im asking is, does the substrate absolutely need to have a tertiary LG in order to get the hoffman product or will a secondary LG give a mix of zaitsev/hoffman products and not purely zaitsev under appropriate conditions?

 

[Kahr]

Whenever I see bulky base (LDA, t-butoxide), I go with the hoffman product (major), otherwise go zaitsev if not bulky.

I think if you've got a secondary, i.e. the H on the beta carbon isn't too sterically hindered (as in your example), then you'll probably get some zaitsev as well, but I'd still go with the hoffman as the major product, whereas if both the base and the beta carbon are "bulky", there's no question it's hoffman.

 

[Dotoday]

The halide does not need to be tertiary. Secondary halide with T-butoxide will also yield Hoffman elimination product.