Greenstein Paul D, Casabianca Leah B
Department of Chemistry, Clemson University , Clemson, South Carolina 29634, United States.
J Phys Chem B. 2017 May 18;121(19):5086-5093. doi: 10.1021/acs.jpcb.7b01465. Epub 2017 May 10.
Using proton and carbon chemical shifts, we investigated the self-association of three isomers of naphthalenedicarboxylic acid, a model for the aggregation of asphaltenes. Experimental proton chemical shifts of each isomer were measured as a function of concentration in an aprotic solvent. Several potential structures of the monomer and dimer of each naphthalenedicarboxylic acid were considered, and calculated proton chemical shifts for the potential monomer and dimer structures were compared to the experimental chemical shifts to find the weighted average structure that best fit the experimental shifts. Calculated carbon chemical shifts were also compared to experimental values. The chemical shift comparison and calculated energies indicate that π-stacked dimers are not likely to contribute significantly to the dimer structure of any of the three naphthalenedicarboxylic acid isomers studied.
利用质子和碳化学位移，我们研究了萘二甲酸三种异构体的自缔合，这是沥青质聚集的一个模型。在非质子溶剂中，测量了每种异构体的实验质子化学位移随浓度的变化。考虑了每种萘二甲酸单体和二聚体的几种可能结构，并将潜在单体和二聚体结构的计算质子化学位移与实验化学位移进行比较，以找到最符合实验位移的加权平均结构。计算得到的碳化学位移也与实验值进行了比较。化学位移比较和计算能量表明，π堆积二聚体不太可能对所研究的三种萘二甲酸异构体中任何一种的二聚体结构有显著贡献。
