Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
 
Pressure Effect on the Reorientational Correlation Time of Water in Formamide–Water Mixtures at 25 °C
Masaki OkadaKazuyasu IbukiMasakatsu Ueno
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2013 Volume 86 Issue 4 Pages 452-463

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Abstract

NMR spin–lattice relaxation times (T1) for nucleus D of D2O in deuterated formamide (FA-d3)–D2O mixtures were measured up to 80 mol % of FA-d3 at 25 °C under pressure up to 196.1 MPa. To discuss the pressure effect on the dynamic behavior of water molecules in the mixtures, the reorientational correlation times (τc) of D2O molecules were estimated from the quadrupole coupling equation. τc monotonously increased with increasing FA-d3 content at all pressures studied. However, τc apparently decreased with increasing pressure until 20 mol % of FA-d3, while over 40 mol % of FA-d3 the pressure coefficient of τc (∂τc/∂P) became positive and larger with increasing FA-d3 content. A negative pressure coefficient would indicate the existence of three-dimensional hydrogen-bonded network structure of water, and a positive one would be ascribed to the strengthening of dipole interactions and hydrogen bonds between FA-d3 and D2O by compression. In order to investigate the pressure effect on the reorientational dynamics of water molecules in detail, we performed molecular dynamics (MD) simulations paying attention to the pressure effect on hydrogen-bonding and dipole interactions.

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© 2013 The Chemical Society of Japan
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