2-(4′-正烷基苯)-4,6-二羟基-5-烷基嘧啶类液晶的EI质谱研究

Mass Spectra of Liquid Crystals of 2-(4′-alkylbenzyl)-5-alkyl-4,6-dihydroxyl-pyrimidine Derivatives

报道了2-(4′-正烷基苯)-4,6-二羟基-5-烷基嘧啶类衍生物的电子轰击源(EI)的质谱行为,通过对10种不同取代基嘧啶类衍生物的质谱研究,推测了该类化合物的质谱裂解机理。该类化合物离子的主要特征是均有较强的分子离子;其基峰离子是由于嘧啶环烷基的β位处断裂,形成基峰离子[R2C6H4C4N2(OH)2CH2]+;碎裂离子主要是由于嘧啶环断裂所致,从而形成[R2C6H4C2N2OH]+、[R2C6H4CN]+·、[R2C6H4C]+等一系列特征离子。

The 2-（4＇-alkylbenzyl）-5-alkyl-4,6-dihydroxyl-pyrimidines are a series of important liquid crystals of TN. They have been used widely in physics, chemistry, electronics fields and so on. Due to its particular characters, more and more chemists and physicists have been interested in it. In the paper, the EI mass spectra of 10 classes of 2-（4＇-alkylbenzyl）-5-alkyl-4,6-dihydroxyl-pyrimidine derivatives are presented. According to the ten kinds of the spectra, the intensities of molecular ions of the compounds are very strong. The basic peaks are caused by 2-（4＇-alkylbenzyl）-5-alkyl-4,6-dihydroxylpyrimidine derivatives cleaved from β position of 5-alkyl, and other main fragment ions are caused due to the cyclo-pyrimidine cleavage. Simultaneously, the substituted R1 and R2 can be rationalized according to the value of molecular ion and the value of base peak of this kinds of compounds.