1位置換シクロヘキサン-3,5-ジオン類の電子衝撃イオン化におけるフラグメンテーション機構の研究

概要

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EI mass spectral fragmentation of 1-X-cyclohexane-3,5-diones (X=CH2, O, S) has been investigated by using MO calculation. It has been revealed that the first bond cleavage occurs at either 2-3 or 5-6 bond corresponding to α-cleavage with respect to carbonyl group and 1-X, followed by two competitive bond cleavage giving [M-CO]+· or [M-CH2X]+·, respectively.The potential energies of CO or CH2X elimination from the acyclic molecular ion have been determined by MNDO. In 1-oxa compounds, the CO elimination process is energetically more favorable than the CH2X elimination process, while the CH2X elimination process is more favorable in 1-thia compounds.This result is in good agreement with the relative intensities of fragment ions [M-CO]+· and [M-CH2X]+·.In addition to the above description, the effect of 1-X on ring-bond cleavage has been discussed.
日本質量分析学会の論文