# Reaction of 1 equivalent of Mg in ether with 1,4-dibromobut-2-yne

What will be the product formed the if the reaction of Mg in ether with 1,4-dibromobut-2-yne occurs? At first, I thought the answer would be cyclobutyne, but the correct answer is buta-1,2,3-triene.

• Cyclobutyne cannot exist. – orthocresol May 18 '19 at 17:46

$$\ce{Br\overset{+}{Mg}\overset{-}{C}H2-C#C-CH2Br <-> Br\overset{+}{Mg}CH2=C=\overset{-}{C}-CH2Br}$$
• Sorry, I've noticed you've been struggling with formatting for a while and IMO it's visually better to put charges above with \overset{<above>}{<below>} command so that the skeletal structure is preserved – it's then arguably easier to visually compare both structures, like so (you can right-click on the formula and select Show Math As → TeX Commands): $$\ce{Br\overset{\large +}{Mg}-\overset{\large -}{C}H2-C#C-CH2Br <-> Br\overset{\large +}{Mg}-CH2=C=\overset{\large -}{C}-CH2Br}$$ Just a suggestion:) – andselisk May 18 '19 at 19:23