Electron ionization mass spectra, ionization, and appearance energies and bond energies (as dissociation energies) are reported for benzoic acid-1-methyl-ethyl ester (BAIPE), benzoic acid-1-deutero-1-methyl-ethyl ester (BAIPED1), benzoic acid-2,2,2-trideutero-1-trideuteromethyl-ethyl ester (BAIPED6) as well as nicotinic acid-1-methyl-ethyl ester (NAIPE), nicotinic acid-1-deutero-1-methyl-ethyl ester (NAIPED1), and nicotinic acid-2,2,2-trideutero-1-trideuteromethyl-ethyl ester (NAIPED6). Ionization energies of 9.39 eV for BAIPE, 9.40 eV for BAIPED1, 9.26 eV for BAIPED6 as well as 9.70 eV for NAIPE, 9.79 eV for NAIPED1, and 9.65 eV for NAIPED6 were determined. A gas-phase formation enthalpy of Δ H f 0 = (−4.10 ± 0.1) eV for BAIPE is calculated as well as Δ H f 0 = (−3.35 ± 0.1) eV for NAIPE. Molecular ions show two main fragmentation pathways. The first is a classical McLafferty rearrangement, characterized by the transfer of one γ-hydrogen atom from the isopropyl ester chain leading to the ions of the corresponding acid and neutral propene. The second is the double hydrogen transfer from the ester chain leading to the formation of the protonated acid and a C3H5√ allyl radical. For BAIPE, both hydrogen atoms originate from the methyl groups of the aliphatic chain with a probability of ≥98%, whereas the C-1-hydrogen is transferred with a probability of ≤2%. For NAIPE, both hydrogen atoms originate from the methyl groups of the aliphatic chain with a probability of 90%. Experimental proton affinities of PA = (8.75 ± 0.2) eV for benzoic acid and PA = (8.43 ± 0.2) eV for nicotinic acid are derived. For the protonation of the carbonyl group, B3LYP DFT calculations yielded PA = 8.66 eV for benzoic acid and PA = 8.41 eV for nicotinic acid. The overall fragmentation mechanism is explained with the initial formation of a 1,5-distonic ion by transfer of the first hydrogen. For the transfer of the second hydrogen, an intermediate ion/neutral complex is formulated.

中文翻译：

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未氘化和氘化苯甲酸异丙酯和烟酸异丙酯的电子诱导电离：对麦克拉弗蒂重排机制的一些影响

报告了苯甲酸-1-甲基-乙酯 (BAIPE)、苯甲酸-1-氘代-1-甲基-乙酯 (BAIPED1) 的电子电离质谱、电离、出现能和键能（作为解离能） , 苯甲酸-2,2,2-trideutero-1-trideuteromethyl-ethylester (BAIPED6) 以及 nicotinic acid-1-methyl-ethylester (NAIPE), nicotinic acid-1-deutero-1-methyl-ethylester (NAIPED1) 和烟酸-2,2,2-trideutero-1-trideuteromethyl-乙酯 (NAIPED6)。确定了 BAIPE 的电离能为 9.39 eV、BAIPED1 的 9.40 eV、BAIPED6 的 9.26 eV 以及 NAIPE 的 9.70 eV、NAIPED1 的 9.79 eV 和 NAIPED6 的 9.65 eV。计算出 BAIPE 的气相形成焓 Δ H f 0 = (-4.10 ± 0.1) eV 以及 NAIPE 的 Δ H f 0 = (-3.35 ± 0.1) eV。分子离子显示出两种主要的碎裂途径。第一个是经典的麦克拉弗蒂重排，其特征是从异丙酯链转移一个 γ-氢原子，导致相应的酸和中性丙烯的离子。第二个是酯链的双氢转移导致质子化酸和 C3H5√ 烯丙基的形成。对于BAIPE，两个氢原子均以≥98%的概率来源于脂肪链的甲基，而C-1-氢以≤2%的概率转移。对于 NAIPE，两个氢原子均来自脂肪链的甲基，概率为 90%。实验质子亲和力 PA = (8.75 ± 0.2) eV 苯甲酸和 PA = (8.43 ± 0.2) eV 烟酸。对于羰基的质子化，B3LYP DFT 计算得出 PA = 8。苯甲酸为 66 eV，烟酸为 PA = 8.41 eV。通过第一个氢的转移最初形成 1,5-不等离子离子来解释整个碎裂机制。为了转移第二个氢，配制中间离子/中性复合物。