Department of Chemistry, Wright State University, Dayton, Ohio 45435, United States.
J Phys Chem A. 2020 Mar 19;124(11):2152-2159. doi: 10.1021/acs.jpca.9b11964. Epub 2020 Mar 5.
Carbon acids are compounds which ionize by dissociating along carbon-hydrogen bonds. Although commonly noted for the extremely low acidities of some members of this class, these compounds in fact display a wide range of ps and upon proper substitution can even form strong acids. This study employs density functional theory to estimate the gas-phase acidities (Δ°s) of these compounds and applies a quantitative structure-activity relationship (QSAR) method at the B3LYP/6-31+G** level with the CPCM aqueous solvent model to estimate their aqueous ps. For the latter study, the energy difference Δ(HO) in water between the parent compounds and their dissociation products was used as a single parameter. Good quality QSAR regression equations were obtained for both the gas-phase ( = 0.9905) and aqueous ( = 0.9647) dissociations. These equations should be useful for the estimation of missing ps for compounds in this class. A general discussion of the features affecting the ps of these compounds is also given.
碳氢酸是通过沿碳氢键解离而电离的化合物。尽管这类化合物的某些成员的酸度极低是众所周知的，但实际上它们显示出广泛的酸度范围，并且经过适当取代，甚至可以形成强酸。本研究采用密度泛函理论估算这些化合物的气相酸度（Δ°s），并应用 B3LYP/6-31+G**水平的定量结构-活性关系（QSAR）方法和 CPCM 水溶剂模型估算它们的水相酸度。在后一种研究中，将母体化合物与其离解产物之间在水中的能量差Δ(HO)用作单个参数。对于气相（ = 0.9905）和水相（ = 0.9647）离解，都得到了高质量的 QSAR 回归方程。这些方程对于估算该类化合物中缺失的酸度值应该是有用的。还对影响这些化合物酸度的特征进行了一般性讨论。
