Chemistry

THF Up Close

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Science  14 Apr 2006:
Vol. 312, Issue 5771, pp. 161
DOI: 10.1126/science.312.5771.161c

Although molecules in the liquid state are in constant random motion, they appear to adopt specific average configurations that account for such properties as heat capacity and solvation. Insight into these configurations has come mainly from theoretical simulations, whose accuracy is gauged by the extent to which bulk properties are correctly predicted. The pentagonal (CH2)4O tetrahydrofuran (THF) is a widely used solvent in organic synthesis because of its relatively high polarity in the absence of hydrogen bonding capacity.

Bowron et al. have taken advantage of progress in neutron scattering technology to probe the molecular structure of liquid THF at room temperature directly. Because neutrons are scattered preferentially by protons, the authors refined their analysis by comparing spectra of protiated and deuterated THF, as well as a 1:1 mixture of the isotopomers. Computer modeling of the data revealed a propensity for T-shaped interaction geometries, in which adjacent molecules were oriented edge to face. This arrangement leads to 2.5-Å diameter void spaces, which may account for the solvent's capacity to harbor free electrons. — JSY

J. Am. Chem. Soc. 128, 10.1021/ja0583057 (2006).

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