Infrared Study of the Association Between Phenol and 1‐Azabicyclo(4,4,0)Decane (Quinolizidine) Derivatives

Abstract

The following values of the thermodynamic functions for the association by H bonding of phenol with I-azabicyclo(4,4,0)decane (quinolizidine) derivatives in tetrachlorethylene solution, have been determined from infrared measurements: I-azabicyclo(4,4,0)decane (I): -AH": 9.8 1 0 . 5 kcal/mole, -AGO: 2.5 1 0 . 5 kcal/ mole, -AS": 24.612 e. In connection with the spectroscopic determination of the stereochemistry of l-azabicyclo(4,4,0)decane (quinolizidine) [2] derivatives, the 1,3 non bonded interactions with the nitrogen lone pair have been correlated by infrared spectroscopy measurements with the association constant of the lone pair and the proton donor Phenol was chosen as proton donor. Although phenol is self-associated, and dimerization at low concentrations occurs, the error due to this association is small. The donor properties of phenol are almost optimal as the bonding is strong enough to be measured accurately.Finally, T. Gramstad [3] has shown that steric effects are enhanced when phenol is used as donor instead of methanol. For these reasons we expected an optimal differenciation of the measured effects.( fig. 1). DETERMINATION OF THE ASSOCIATION CONSTANTSThe association constants were measured using the free vOt, band at 3610 cm-' in a dilute solution of phenol (6 m Mole/l max. to prevent self-association) in the presence of a large excess of acceptor.