Symmetry Bias in H-Bonded Crystals
Abstract
The Cambridge Crystallographic Data Base (CCDB) was searched for all examples of small molecules with nitroaniline groups. This data set was divided into primary and secondary nitroanilines (32 compounds), tertiary nitroanilines (36 compounds). For the primary and secondary nitroanilines, which can form nitroaniline hydrogen bonds, 41% of the crystals were acentric. For each set we determined what percent of the crystal structures were acentric. For the tertiary nitroanilines, without-NH sub 2--O sub 2 N hydrogen bonds, 17% were acentric. These numbers are to be compared to the frequency of occurrence of acentricity in the CCDB for the total population of all organic molecules. This number was determined several years ago when the data base container about 40, 000 structures. At that time 25% of the structures were acentric. Within that set it is estimated that most of the acentric structures contain resolved chiral compounds. Thus, a better, yet generous, estimate for our purposes would be that only about 10% of all racemic or achiral compounds pack in acentric crystal structures. Thus, there appears to be a significant bias towards crystallographic acentricity for the primary and secondary nitroaniline structures. Further work is in progress to determine if the hydrogen-bond patterns in the primary and secondary nitroaniline class are themselves acentric. (Author) (KR)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 23, 1990
- Accession Number
- ADA225620
Entities
People
- K. S. Huang
- M. C. Etter
Organizations
- University of Minnesota