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Reorientation dynamics in liquid alcohols from Raman spectroscopy
Author(s) -
Lin Ke,
Hu Naiyin,
Zhou Xiaoguo,
Liu Shilin,
Luo Yi
Publication year - 2012
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2997
Subject(s) - chemistry , alcohol , raman spectroscopy , methanol , relaxation (psychology) , picosecond , molecule , spectroscopy , aqueous solution , chemical physics , translational motion , hydrogen bond , molecular dynamics , computational chemistry , organic chemistry , physics , optics , social psychology , laser , classical mechanics , quantum mechanics , psychology
Polarized Raman spectroscopy has been employed to study the reorientational, or more specifically the translational relaxation dynamics, of alcohol molecules in pure liquids and aqueous solutions. It is found from the spectral width measurements that alcohol molecules in pure liquids have typically translational relaxation times on the order of picoseconds, following the order methanol < ethanol < i ‐propanol < n ‐propanol. Temperature‐dependent measurements show that hydrogen‐bonding (HB) and hydrophobic interactions control the translational motion. The hydrophobic interaction reduces the relaxation time more apparently in view of the CH 3 group than the skeleton motion. For alcohol–water mixtures, the increase of water concentration generally slows down the relaxation process in a non‐monotonic behavior. However, the trend stops at a certain point and the motion of alcohol molecules becomes faster when the alcohol concentration further drops. Different mechanisms have been proposed to interpret these observations, which might be helpful to gain deeper insight into the HB networks of alcohols with water. Our study strongly illustrates that Raman spectroscopy can be applied to the study of fast translational motion of molecules in HB systems. Copyright © 2011 John Wiley & Sons, Ltd.