Stable conformations of 12‐crown‐O₃N and its Li⁺ complex in aqueous solution

Abstract

Stable conformations of 12-crown-O3N and its Li complexes in aqueous solution were investigated. To calculate the free energy differences of conformers of 12-crown-O3N and its Li+ complex, our procedure was to make use of two programs, CONFLEX and BOSS. The former generates conformers, and the latter calculates the differences in free energy of solvation between two conformers in aqueous solution. It was confirmed that the present procedure is applicable in solving the question of what is the most stable conformation of 12-crown-O3N in aqueous solution. Results of the calculations suggest that the order of stability for conformers in a vacuum is different from that in aqueous solution. It was also confirmed that the coordination geometry of solvent waters to Li+ changes depending on the distance between the cation and the crown ring.

Molecular Structure Determination Using Chiroptical Spectroscopy: Where We May Go Wrong?

“…). This deficiency in the CONFLEX program has been previously noted . One might wonder why one would want to work with salts of carboxylic acids for determining the absolute configurations when the common practice is to convert the acids to corresponding esters.…”

“…This deficiency in the CONFLEX program has been previously noted. 36 One might wonder why one would want to work with salts of carboxylic acids for determining the absolute configurations when the common practice is to convert the acids to corresponding esters. However, salts provide important sources of scientific enquiry: (a) It is easier to convert an acid to its corresponding base form (by titration).…”

Chiroptical Spectroscopy of Natural Products: Avoiding the Aggregation Effects of Chiral Carboxylic Acids

“…However, the conformational search yielded unrealistic geometries with Na + ions far removed from the rest of the molecule. Following communications with CONFLEX technical support we decided that the CONFLEX program is not suitable for conformational search of ionic species, and this deficiency in the CONFLEX program has been noted previously …”

“…Following communications with CONFLEX technical support we decided that the CONFLEX program is not suitable for conformational search of ionic species, and this deficiency in the CONFLEX program has been noted previously. 40 The two lowest energy conformers of HADNa are shown in Figure 1. One would normally expect each sodium cation to be near a carboxylate group, perhaps symmetrically placed between the two oxygen atoms of the carboxylate anion.…”

First Room Temperature Chiral Anionic Liquid Forming Micelles and Reverse Micelles

“…The conformation of T12M was generated utilizing the conformational search with CONFLEX program as follows. Since CONFLEX program does not handle the ionic species properly, 52 a molecular model of diacetyl-L-tartaric acid was input into the CONFLEX program and conformational search was undertaken using MMFF94S molecular mechanics force field. The 115 conformers obtained within 7 kcal/mol are further optimized at B3LYP/aug-cc-pVDZ/PCM level.…”