THE STRUCTURE AND THERMODYNAMICS OF HYDROGEN BONDING INTERACTIONS OF OCN- WITH METHANOL, FORMAMIDE, AND N-METHYLFORMAMIDE

摘要

The primary solvation sphere surrounding the cyanate anion in nonaqueous protic solvents contains intimate hydrogen bonds with this anion. These interactions perturb the electron density and vibrational modes in OCN-, as revealed experimentally by NMR and infrared spectroscopies. In neat methanol solutions of 0.1 M tetrabutylammonium cyanate, the anion participates in three distinct-complexes: OCN-... HOMe, OCN-...(HOMe)(2), and MeOH ... OCN-... HOMe. At the same concentration in formamide solutions, only one is observed, the OCN-...(FA)(2) species, whereas in N-methylformamide solutions two solvates are present: OCN-... NMF and OCN-...(NMF)(2). The thermodynamics for the formation of these complexes have been studied in nitromethane solutions in order to understand the factors involved in anion solvation. The differences observed in the extent of solvation of the cyanate anion by these protic solvents have been related to the self-association of the neat solvents. [References: 26]