Reorientation dynamics in liquid alcohols from Raman spectroscopy

QC 20120228
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 –CH3 group than the skeleton motion. For alcohol–water mixtures, the increaseofwater 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.

Hu, NaiyinUniversity of Science and Technology of China (author)
Zhou, XiaoguoUniversity of Science and Technology of China (author)
Liu, ShilinUniversity of Science and Technology of China (author)
Luo, Yi,1965-KTH,Teoretisk kemi och biologi(Swepub:kth)u126eitw (author)
University of Science and Technology of ChinaTeoretisk kemi och biologi (creator_code:org_t)

By the author/editor: Lin, Ke; Hu, Naiyin; Zhou, Xiaoguo; Liu, Shilin; Luo, Yi, 1965-

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NATURAL SCIENCES: NATURAL SCIENCES; and Chemical Science ...; and Physical Chemist ...

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