Salt Effects on the Rates and Mechanisms of Solvolysis Reaction of Organic Halides and Water Structure Distortion in N,N-Dimethylformamide- and N,N-Dimethylacetamide-Water Mixed Solvents
Salt Effects on the Rates and Mechanisms of Solvolysis Reaction of Organic Halides and Water Structure Distortion in N,N-Dimethylformamide- and N,N-Dimethylacetamide-Water Mixed Solvents
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DOI：
10.1246/bcsj.20090329
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发表时间：
2010-04-15
影响因子：
4
通讯作者：
Nakano, Toshiyuki
中科院分区：
文献类型：
--
作者：
Hojo, Masashi;Ueda, Tadaharu;Nakano, Toshiyuki
在50% (v/v) DMF-和DMA-H2O的混合溶剂中，考察了盐对脂肪族卤化物及其相关化合物（RX）溶解反应速率的影响。在50% (v/v) DMF-和DMA-H2O混合溶剂中，加入碱金属和碱土金属高氯酸盐或多种四烷基铵盐后，所有典型的s - n(1)和s - n(2)底物的“伪”一阶速率常数（k/s(-1)）与以往在其他有机溶剂体系（如50% （v/v）丙酮-、1,4-二氧六环-或亚砜- h2o）中得到的结果相比，均无异常行为。对1-金刚烷酰溴的δ对数(k/s(-1))/ δ [LiClO4]与有机溶剂（CH3CN、DMA和DMSO）含量的详细考察表明，所观察到的不同盐效应是由溶剂对离去基阴离子和金属阳离子的不同溶剂化能力引起的。作为本文的一个新亮点，我们能够证明LiClO4对溶剂溶解速率的影响与气相中RX的吉布斯自由能值（δ G度）表示的碳正离子稳定性之间的比例或相关性。基于DMA-H2O和DMA-D2O以及DMF-D2O混合溶剂的拉曼光谱，讨论了体水结构的畸变。
In 50% (v/v) DMF- and DMA-H2O mixed solvents, salt effects on the solvolysis reaction rates of aliphatic halides and related compounds (RX) have been examined for further exploring. Compared with previous results obtained in other organic solvent systems, such as 50% (v/v) acetone-, 1,4-dioxane-, or sulfolane-H2O, no exceptional behavior was observed in the "pseudo" first-order rate constants (k/s(-1)) of all the typical S-N(1) and S-N(2) substrates by the addition of alkali metal and alkaline earth metal perchlorates or many kinds of tetraalkylammonium salts in 50% (v/v) DMF- and DMA-H2O mixed solvents. The detailed examination of Delta log(k/s(-1))/Delta[LiClO4] for 1-adamantyl bromide vs. the contents of organic solvents (CH3CN, DMA, and DMSO) suggested that the observed different salt effects were caused by the different solvation abilities of the solvents toward the leaving-group anion as well as the metal cation. As a new highlight in the present paper, we were able to demonstrate a proportionality or correlation between the LiClO4 effects in the solvolysis rates and the carbocation stabilities expressed by the Gibbs free energy values (Delta G degrees) of RX in the gas phase. Based on the Raman spectra of DMA-H2O and DMA-D2O as well as DMF-D2O mixed solvents, we discuss the distortion of the bulk water structure.