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首页> 外文期刊>Bulletin of the Chemical Society of Japan >Gas-Phase Lithium Cation Basicities of Acetophenones:A Linear Relationship between Lithium Cation and Proton Basicities
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Gas-Phase Lithium Cation Basicities of Acetophenones:A Linear Relationship between Lithium Cation and Proton Basicities

机译：苯乙酮的气相锂阳离子碱性：锂阳离子与质子碱性之间的线性关系

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摘要

The free energy changes(AG)for the reaction B2Li+=Li+ + 2B were obtained in the gas phase for m-and p-substituted acetophenones based on the measurement of ligand-exchange equilibria of the type LiA2+ + 2B=LiB2+ + 2A using a FT-ICR spectrometer.A plot of AG(relative lithium cation basicity,ALCB[B2Li+])values against the AGB(proton basicity)showed a limited linear correlation for meta substituents and para electron-withdrawing groups with a slope of 1.06.Negative deviations observed for strong pi-donor susbstituents suggested that the resonance effect of these substituents is reduced in the Li+ complex compared to that in the protonated ion.Based on the correlation analysis using the Yukawa-Tsuno equation,ALCB=rho(sigma deg + r+(DELTA sigma_R)+),the substituent effect on DELTA LCB[B2Li+]of acetophenone was characterized by a p value of -12.5 and an r+ value of 0.49.A p value of -8.3 was determined for DELTA LCB[BLi+]based on the reaction LiB+=Li+ + B from a rho value for DELTA LCB[B2Li+]by using a factor of 1.5 that was obtained from a linear relationship between calculated ALCB[B2Li+]and DELTA LCB[BLi+].In comparison with the corresponding results for other Lewis cation basicities,it was shown that the p value decreases in the order of H+(-11.6)> Me3Si+(-11.0)> Me3Ge+(-9.7)> Li+(-8.3).The decrease in the p value indicates that the positive charges at the Lewis cation moiety of the adduct ion increases in this order.The small p value for the Li+ basicity is consistent with largely ionic(ion-dipole interaction)nature of the bonding interaction between Li+ and the carbonyl oxygen atom.The r+ value that indicates the degree of charge-delocalization into the aromatic pi-system also decreases in the same order.In spite of a small charge transfer from Li+ to acetophenone ligand,the moderate r+ value of 0.49 observed for the Li+ complex is interpreted to be due to the redistribution of the induced positive charge in the acetophenone moiety by binding with Li+.
机译：基于LiA2 + + 2B = LiB2 + + 2A型配体交换平衡的测量，在m和p取代的苯乙酮的气相中获得了反应B2Li + = Li + + 2B的自由能变化（AG）。 FT-ICR光谱仪.AG（相对锂阳离子碱度，ALCB [B2Li +]）值与AGB（质子碱度）值的关系图显示，亚取代基和对位吸电子基团的线性相关性有限，斜率为1.06。观察到的强pi供体替代物表明，与质子化离子相比，Li +络合物中这些取代基的共振效应有所降低。基于Yukawa-Tsuno方程的相关分析，ALCB = rho（sigma deg + r +（ DELTA sigma_R）+），其对苯乙酮对DELTA LCB [B2Li +]的取代作用的p值为-12.5，r +值为0.49。基于反应，对于DELTA LCB [BLi +]，p值为-8.3。 LiB + = Li + + B从DELTA LCB [B2Li +通过使用从计算的ALCB [B2Li +]和DELTA LCB [BLi +]之间的线性关系获得的1.5因子。与其他Lewis阳离子碱度的相应结果相比，表明p值按顺序降低H +（-11.6）> Me 3 Si +（-11.0）> Me 3 Ge +（-9.7）> Li +（-8.3）.p值的降低表明加合物离子的Lewis阳离子部分的正电荷按此顺序增加。 Li +碱度的小p值与Li +和羰基氧原子之间键合相互作用的大部分离子性质（离子-偶极相互作用）相符.r +值也表示电荷离域到芳香族pi系统中的程度尽管从Li +到苯乙酮配体有少量电荷转移，但Li +配合物观察到的中等r +值为0.49，这被解释为归因于苯乙酮与苯甲酸酯键合后诱导的正电荷在苯乙酮部分中的重新分布。李+。

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