Journal of Physical Chemistry B, Vol.113, No.35, 11950-11958, 2009
Hydration Modes of an Amphiphilic Molecule: NMR, FTIR, and Theoretical Study of the Interactions in the Water-Lutidine System
Using H-1 and C-13 NMR spectra and relaxations, PFG NMR diffusion measurements, FTIR spectra, and quantum-chemical structure predictions and optimizations on the MP2/6-31G(d) level, we have studied interactions between water (W) and lutidine (2,6-dimethylpyridine, Q in a wide range of ratios. At low W content up to 35%, W was found to bind to 1, by an O-H center dot center dot center dot N hydrogen bond and form transient L-W aggregates containing two to four L molecules in cooperation with two to three other W molecules. At higher W content, these aggregates are gradually cleaved to single L molecules enwrapped by a hydration shell anchored in an O-H center dot center dot center dot N hydrogen bond, At all compositions of the mixture, the various hydrate forms are in fast mutual exchange with a correlation time on the order of 1 x 10(-5) s.