Collision-induced dissociations of carboxylate negative ions from 2-ethylbutanoic, 2-methylpropanoic, and pivalic acids. An isotopic labelling study
作者:Michael B. Stringer、John H. Bowie、Peter C. H. Eichinger、Graeme J. Currie
DOI:10.1039/p29870000385
日期:——
Deprotonation of Et2CHCO2H yields Et2CHCO2–. On collisional activation this ion forms CO2–˙, CH2CH–, and MeCHCH–. In addition, elimination of H˙ and Et˙ yield Et(R)CCO2–˙(R = Et and H, respectively). The elimination of Et˙ is not a simple cleavage but occurs by loss of H˙ from a methyl group followed by loss of ethene. The carboxylate ion also rearranges to Et2CCO2H; this species decomposes to HO–, EtCCH2
Et 2 CHCO 2 H去质子化生成Et 2 CHCO 2 –。上碰撞活化该离子形成CO 2 - ˙,CH 2 CH - ,和机甲CH - 。此外,消除H +和Et-会产生Et(R)C CO 2 –(分别为R = Et和H)。Et 3的消除不是简单的裂解,而是通过甲基中H 3的损失然后乙烯的损失而发生的。羧酸根离子也重排为Et 2 CCO 2 H;该物种分解为HO –,EtC CH 2,并且也消除了C 3 H 8和CH 4的元素。已使用2 H和13 C标记研究了所有片段化:例如,建议通过六步法逐步进行Et 2 CCO 2 H中CH 4的损失,其中第一步(形成起始甲基阴离子)决定利率。的Et的碰撞活化质谱2 CHCO 2 -中,Me 2 CHCO 2 - ,和Me 3 CCO 2 -不同,都表现出特征分解。例如,所有三个离子都消除了甲烷。每种情况下的机制都不相同。