[Study on the distribution and structure of polyhalides by gas chromatography-mass spectrometry]

A series of unexpected products were obtained when 1,4-dichloro-2-butyne reacted with allyl bromide with the catalyst PdCl2 (PhCN)2. It is difficult to separate these products from each other and to identify the structure of each one due to their similar properties. In order to solve this problem, gas chromatography-mass spectrometry (GC-MS) was chosen to analyse the above products because of its good sensitivity and selectivity. The analytical results showed that (A) the 8 compounds were 5,6-dichloro-4-chloromethyl-1, (E) 4-hexadiene (III), 5,6-dichloro-4-chloromethyl-1, (Z) 4-hexadiene (IV), 5-bromo-6-chloro-4-chloromethyl-1, (E) 4-hexadiene (V), 5-bromo-6-chloro-4-chloromethyl-1, (Z) 4-hexadiene (VI), 5-bromo-6-chloro-4-bromomethyl-1, (E) 4-hexadiene (VII), 5-bromo-6-chloro-4-bromomethyl-1, (Z) 4-hexadiene (VIII), 5,6-dibromo-4-bromomethyl-1, (E) 4-hexadiene (IX) and 5,6-dibromo-4-bromomethyl-1, (E) 4-hexadiene (X). Most compounds, except (V) and (VI), were the results of exchange reaction between chloride and bromide anion; each pair of the products are geometrical isomers. (B) in the four pairs of geometrical isomers, the ratio of Z-isomer/E-isomer decreased from 95:5 to 53:47 as molecular weight increased from compounds (III) and (IV) to compounds (IX) and (X).