ASSOCIATIVE BEHAVIOR OF BENZYL ALCOHOL IN CARBON-TETRACHLORIDE SOLUTIONS

Self-association of benzyl alcohol in carbon tetrachloride has been st udied by infrared absorption spectroscopic measurements in the fundame ntal OH-stretching vibration region. Infrared spectra were acquired at 30, 40, and 50 degrees C for varying alcohol molalities, the highest concentration bring 0.2 mol/kg. The spectra were collected in a data m atrix and analyzed by multivariate resolution methods in order to dete rmine the numbers of different components present in the solution and to find the spectra and concentration profiles of each component. The result indicates that the spectral variance can be described by three components, free alcohol monomers, open chain oligomers, and cyclic ol igomers. The resolved spectra show one sharp band at 3620 (-1) for the component representing the hydroxyl group of free alcohol molecules a nd one broad band at cm 3300 cm-' for the component representing the h ydroxyl groups of cyclic alcohol aggregates. The component representin g the hydroxyl groups of open chain aggregates appears with two absorp tion bands, one broad and asymmetric band at 3500 cm(-1) and a smaller band at 3600 cm(-1). The small band at 3600 cm(-1) is connected to th e hydroxyl group situated at the ''free-end'' of the chain, while a br oad and asymmetric band at 3500 (-1) is connected to the hydroxyl grou ps situated inside and at the ''bound-end'' of the chain. The average cm number of alcohol monomers in the H-bonded aggregates decreases wit h increasing temperature in the solution, It was equal to 4 for open c hain aggregates at 30 degrees C and equal to 3 at 40 and 50 degrees C. The corresponding numbers for the cyclic aggregates were 7 at 30 degr ees C and 6 at 40 and 50 degrees C. The calculated concentration profi les show that the alcohol monomers are the dominating component throug hout the concentration range investigated and that there are more open chain oligomers than cyclic aggregates present.