ISSN:
0894-3230
Keywords:
Organic Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The conformational properties of diethyl disulphide, a model compound for the disulphide bridges in peptides and proteins, were studied with ab initio methods. Stationary point structures were optimized at the HF/6-31G* level with consideration of electron correlation in subsequent single-point MP2 calculations. The six energy minima were also optimized at the MP2/6-31G* level with calculation of zero-point vibrational frequencies and thermal corrections. Additional single-point MP2 energy calculations employed larger basis sets up to 6-311G(2d, p). With positive disulphide chirality, the global energy minimum is a ‘spiral’ conformation with gauche + C-C-S-S torsion angles. The further stability order for energy minima deviates from previous ab initio results. In particular, the extended trans,trans conformer is subject to a significant relative destabilization on inclusion of electron correlation in the calculations and is only the fifth most stable energy minimum with estimated ab initio ΔH298 = 5·13 kJ mol-1. The results presented are relevant for the discussion of conformational properties for the structurally equivalent disulphide bridges in polypeptides and calculations of relative energies with molecular mechanics methods.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/poc.610070508
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