The methyl C-H blueshift in N,N-dimethylformamide-water mixtures probed by two-dimensional Fourier-transform infrared spectroscopy.
Two-dimensional correlation spectroscopy was used to study the composition-dependent spectral variations of the CH-stretching bands of N,N-dimethylformamide (DMF)-water mixtures with X(DMF) ranging from 0.98 to 0.60. By a detailed correlation analysis of the spectral changes of the CH- and OH-stretching bands, it is found that the intensities of the CH and OH bands change in different ways when the water content is increased. It is also found that two different regions of the water content can be distinguished, in which the intensity changes have different signatures. A tentative explanation for how these phenomena might be related to structural changes in the mixture is proposed. The structural change of DMF induced by the water hydrogen bonded on the carbonyl group is supposed to be the possible origin of the methyl C-H blueshift instead of the direct C-H...O interactions before the hydrophobic hydration takes place.
Xu
Zheng
Z
Department of Chemistry, Zhejiang University, Hangzhou 310027, People's Republic of China.
Li
Haoran
H
Wang
Congmin
C
Pan
Haihua
H
Han
Shijun
S
D000465:Algorithms; D002244:Carbon / Q000737:chemistry; D002627:Chemistry, Physical / Q000379:methods*; D004126:Dimethylformamide; D005559:Formamides / Q000737:chemistry*; D005583:Fourier Analysis; D006859:Hydrogen / Q000737:chemistry; D006860:Hydrogen Bonding; D008745:Methylation; D015233:Models, Statistical; D010100:Oxygen / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods*; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013696:Temperature; D014867:Water / Q000737:chemistry*
D005559:Formamides; D014867:Water; D002244:Carbon; D006859:Hydrogen; D004126:Dimethylformamide; D010100:Oxygen