[alis88]

Please could someone explain why it is not possible to synthesise but-1-yne from butanone?

This reaction is able to occur:

Ar-CO-CH3 --> Ar-CCl2-CH3 --> Ar-CCH

Produced by elimination of 2 moles of HCl from a geminal dihalide, which is in turn produced from an aromatic ketone and PCl5.

Why could a similar reaction not occur for but-1-yne from butanone?

Thanks

Alis

[sjb]

You probably can do similar chemistry, but I think that but-2-yne might be the more stable isomer, look into stability of olefins etc?

[alis88]

I've drawn both reactions out, with the two possible products, i.e. but-1-yne and but-2-yne. I understand how the elimination would commence, but what do you mean when you say that but-2-yne is more substitued?

[alis88]

Oh no, I see! But-2-yne is an internal alkyne so it is more stable than but-1-yne, which is a terminal alkyne.

Thank you so much both of you.

[aldoxime_amine]

just asking, but in the sequence posted by the poster regarding acetophenone, will the second reaction take place through E1CB or E2?

[macman104]

Can you not just use a sufficiently bulky base to produce the hoffman elimination product?

[kiwi]

Can you not just use a sufficiently bulky base to produce the hoffman elimination product?

alternatively, you could use a base like KAPA and get elimination and a zipper reaction occurring to give the desired terminal alkyne