Blackburn A C, Fitzgerald L J, Gerkin R E
Department of Chemistry, Ohio State University, Columbus 43210, USA.
Acta Crystallogr C. 1996 Nov 15;52 ( Pt 11):2862-4. doi: 10.1107/s0108270196008876.
The structure of 2-naphthoic acid, C11H8O2, has been investigated at 153 K in order to determine the degree of disorder of the carboxylic acid group for comparison with that of the room-temperature structure. Analysis of the anisotropic displacement ellipsoids of the carboxyl-O atoms demonstrated that these parameters are wholly consistent with thermal motion of the O atoms. A model with ordered carboxyl-O atoms, but with the acid-H atom refined at two sites with 0.5 occupancy at each, was found to be statistically significantly better than a model with ordered carboxyl-O atoms and an ordered acid-H atom. Thus, as in the room-temperature study, the best structural description is that the O atoms are ordered and the acid-H atom is disordered. Nonetheless, comparisons of the geometric parameters of the carboxyl groups at 296 and 153 K suggest progress toward a fully ordered structure at the lower temperature. Except for the expected slight overall contraction and the slightly altered geometry of the carboxyl group, the structure is virtually the same as at room temperature.
为了确定羧酸基团的无序程度以便与室温结构进行比较，在153 K下对2-萘甲酸（C11H8O2）的结构进行了研究。对羧基-O原子的各向异性位移椭球体的分析表明，这些参数与O原子的热运动完全一致。发现一个羧基-O原子有序，但酸-H原子在两个位置上各以0.5占有率精修的模型，在统计学上比一个羧基-O原子有序且酸-H原子有序的模型要好得多。因此，如同在室温研究中一样，最佳的结构描述是O原子有序而酸-H原子无序。尽管如此，296 K和153 K下羧基基团几何参数的比较表明，在较低温度下朝着完全有序的结构迈进。除了预期的轻微整体收缩和羧基基团几何形状的轻微改变外，该结构实际上与室温下的结构相同。
