The Surprising Dynamics of the McLafferty Rearrangement
The Surprising Dynamics of the McLafferty Rearrangement
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麦克拉弗蒂重排的惊人动态
DOI：
10.1021/acs.jpclett.3c02102
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Sun, Liangliang
中科院分区：
文献类型：
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作者：
Stamm, Jacob;Kwon, Sung;Sandhu, Shawn;Shaik, Moaid;Das, Rituparna;Sandhu, Jesse;Curenton, Bradley;Wicka, Clayton;Levine, Benjamin G.;Sun, Liangliang
我们报告飞秒时间分辨测量的McLaffe重排后的强场隧道电离的2-戊酮，4-甲基-2-戊酮，和4，4-二甲基-2-戊酮。McLaffe产物离子的泵浦-探测依赖的产率拟合为具有快（~ 100 fs）和慢（~ 10 ps）时间常数的双指数函数，其中后者对于后两种化合物更快。在几乎瞬时电离后，快速时间尺度与分子旋转成六元环状中间体有关，这有助于γ-氢的转移，而250 -100倍长的时间尺度与π-键重排和α-和β-碳之间的键断裂有关，以产生烯醇阳离子。这些实验测量支持的从头算分子动力学轨迹，进一步证实了这一重要的逐步反应在质谱的时间尺度。
We report femtosecond time-resolved measurements of the McLafferty rearrangement following the strong-field tunnel ionization of 2-pentanone, 4-methyl-2-pentanone, and 4,4-dimethyl-2-pentanone. The pump–probe-dependent yields of the McLafferty product ion are fit to a biexponential function with fast (∼100 fs) and slow (∼10 ps) time constants, the latter of which is faster for the latter two compounds. Following nearly instantaneous ionization, the fast time scale is associated with rotation of the molecule to a six-membered cyclic intermediate that facilitates transfer of the γ-hydrogen, while the ∼50–100 times longer time scale is associated with a π-bond rearrangement and bond cleavage between the α- and β-carbons to produce the enol cation. These experimental measurements are supported byab initiomolecular dynamics trajectories, which further confirm the time scale of this important stepwise reaction in mass spectrometry.