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The Acidity of Chloro-Substitured Benzenes:A Comparison of Gas Phase,Ab Initio,and Kinetic Data

机译:氯取代苯的酸度:气相,Ab从头算和动力学数据的比较

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The deprotonation energies of benzene,chlorobenzene,all di-,tri-,tetrachlorobenzenes,and pentachlorobenzene have been determined in the gas phase using a Fourier transform ion cyclotron resonance mass spectrometer.The values measured differ only slightly,though significantly,from the corresponding data for oligofluorobenzenes.The heavier halogen acidifies orthopositions slightly less and meta-positions slightly more than fluorine does.Moreover,the contributions of three or more chloro substituents are not perfectly additive.In fact the accmulation attenuates the contributions somewhat.Quantum chemical calculations at the MP2/6-311+G~* level reproduce the gasphase acidities fairly well,but revealspecial effects when extended to experimentally not observable benzenides carrying the halogens at anion-remote positions.Competition experiments have been performed to assess the relative reactivity of nine oligochloro-benzenes towards sec-butyllithium in tetrahydrofuran at -100 deg C.An almost exact linear correlation between logarithmic rates and gaw-phase acidities haw been found.
机译:使用傅立叶变换离子回旋共振质谱仪在气相中测定了苯,氯苯,所有二,三,四氯苯和五氯苯的去质子能。所测得的值与相应数据仅略有不同,尽管有很大差异。与低氟相比,重卤素酸化的原位略少,间位酸化的程度略多于氟。此外,三个或更多氯取代基的贡献也不是完全累加的。事实上,积累会在一定程度上减弱该贡献.MP2上的量子化学计算/ 6-311 + G〜*水平可以很好地再现气相酸度,但是当扩展到实验上无法观察到的在阴离子远程位置带有卤素的苯甲醚时,则显示出特殊的效果。已经进行竞争实验以评估9种低氯氯苯的相对反应性于-100°C下在四氢呋喃中向仲丁基锂已经发现对数速率和gaw相酸度之间存在精确的线性相关性。

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