Acta Crystallographica Section B

Structural Science

Volume 62, Part 4 (August 2006)

research papers

Acta Cryst. (2006). B62, 599-605 [ doi:10.1107/S0108768106015424 ]

Hexamer formation in tertiary butyl alcohol (2-methyl-2-propanol, C₄H₁₀O)

P. A. McGregor, D. R. Allan, S. Parsons and S. J. Clark

Abstract: The crystal structure of phase II of tertiary butyl alcohol (2-methyl-2-propanol, C₄H₁₀O) has been solved using a combination of single-crystal X-ray diffraction techniques and ab initio density functional calculations. This trigonal P $\overline 3$ phase, which is stable at both low temperature and high pressure, and the triclinic P $\overline 1$ phase (phase IV) have very similar enthalpies, the calculations revealing only a 3.859 kJ mol^-1 enthalpy difference at ambient pressure, despite the substantial change of the intermolecular bonding motif from helical catemer to hexamer with an increase in pressure or reduction in temperature. The hexamers in the trigonal phase adopt a chair conformation. There are two unique hexamers: at low temperature these are centred at (0, 0, $1\over2$ ) and ( $2\over3$ , $1\over3$ , 0.961 (13)), and at high pressure the centres are (0, 0, $1\over2$ ) and ( $2\over3$ , $1\over3$ , 0.958 (14)). A slight flattening of the hexamers is observed at high pressure and the calculations confirm that phase II becomes more stable relative to phase IV on pressure increase.

Keywords: hexamer formation; 2-methyl-2-propanol.


	Structure factor file (CIF format) (59.5 kbytes) [ doi:10.1107/S0108768106015424/ws5038Isup2.fcf ] Contains datablock I

	Structure factor file (CIF format) (138.4 kbytes) [ doi:10.1107/S0108768106015424/ws5038thuoh1sup3.fcf ] Contains datablock tbuoh1

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