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RESEARCH PRODUCT

Mass spectra of halogenated esters. Part IX—methyl esters of 2-butenoic acids containing chlorine and/or bromine atom(s)

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The electron impact mass spectra of methyl esters of chloro-, bromo-, dichloro-, bromochloro- and dibromo-2-butenoic acids (13 esters at all) have been investigated. Generally, the peaks due to the following fragments are abundant: M+·, [M OCH3]+, [M CH3OH]+·, [M X]+, [M OCH3 CO]+ or [M COOCH3]+, [M X CH3OH]+ or [M OCH3 HX]+, [M OCH3 CO HX]+, [M OCH3 X X]+ and [M OCH3 CO X X]+. Characteristic for the 2- and 4-halo isomers are the primary losses of a methyl radical and methanol, and for the 3-halo isomers the loss of X· from M+·. Disparities between the spectra of the E and Z isomers are shown, the effect of position of halogen substitution being much more pronounced, as reported previously with the halogenated propenoic acid esters.