Effects of ethanol and dimethyl sulfoxide on the molecular organization of H2O as probed by 1-propanol.
We characterized the effects of ethanol (ET) and dimethyl sulfoxide (DMSO) on H(2)O within a limited H(2)O-rich region by the 1-propanol (1P)-probing methodology developed by us earlier. The results are displayed on a two-dimensional map with twin coordinates: one pertaining to hydrophobicity and the other to hydrophilicity. The locus of ET on this map was at a point in between methanol (ME) and 2-propanol (2P) as expected from our earlier findings by thermodynamic studies. That for DMSO, however, was surprisingly more hydrophilic than ME. Similar to N-methyl groups discussed recently (J. Phys. Chem. B 2011, 115, 2995), it was argued that the methyl groups attached to the S atom are made susceptible for direct hydrogen bonding to the surrounding H(2)O molecules due possibly to the electronegativity of the S atom. In view of these findings, we suggest caution to be exercised for the conventional general trend of taking any methyl groups to be "hydrophobic."
Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522 Japan.
Takeshi
T
Morita
Peter
P
Westh
Keiko
K
Nishikawa
Yoshikata
Y
Koga
D000433:1-Propanol / Q000737:chemistry*; D019840:2-Propanol / Q000737:chemistry; D004121:Dimethyl Sulfoxide / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D014867:Water; D000431:Ethanol; D000433:1-Propanol; D019840:2-Propanol; D004121:Dimethyl Sulfoxide