ISSN:
0894-3230
Keywords:
Organic Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The title compounds (1 and 3, respectively) were studied by X-ray crystal structure analysis. Both are trigonal, space group R3, with lattice parameters a = 27.718(6), c = 8.161(2) Å, Z = 3 and a = 31.267(7), c = 6.560(2), Z = 18, respectively. The dodecamethyl compound 1 is isomorphous with its parent hexakis(4-benzylphenoxy)benzene (2), a known host. However, ‘collapse’ along the c-axial direction has occurred such that the appreciable clathrate cavity of 2 has been replaced by only a very small residual void for 1. Phenol 3 does not pack in discrete [OH]6 hydrogenbonded hexamers; instead, molecules are assembled in infinite chains, linked by OH…O hydrogen bonds of length 2.735(3) Å, which are propagated along threefold screw axes. A variable-temperature CPMAS NMR study of sidechain aryl group rotation in 1 gives a value ΔG≠ of 14.0 ± 0.7 kcal mol-1 (at 42 °C) for the (crystallographically unique) para -disubstituted ring, a similar 14 kcal mol-1 free energy barrier being found hindering rotation of this ring, and of the outer phenyl ring of 1, at 9°C.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/poc.610051003
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