The complete basis set method CBS-QB3 was used in conjunction with the CPCM solvation model to predict both the absolute and relative pKa's of 12 nucleophilic carbenes in dimethyl sulfoxide (DMSO), acetonitrile (MeCN), and water. Average absolute pKa values in DMSO ranged from 14.4 ± 0.16 for 3-methylthiazol-2-ylidene (12) to 27.9 ± 0.23 in the case of bis(dimethylamino)carbene (11), while values in MeCN were determined to be between 25.7 ± 0.16 (12) and 39.1 ± 0.25 (11). Relative pK a calculations yielded similar results. Calculations in aqueous solution gave pKa's between 21.2 ± 0.2 (12) and 34.0 ± 0.3 (11). Excellent agreement between calculated and experimental pK a's was obtained for the few cases where experimental numbers are available, confirming that this theoretical approach may be used to calculate highly accurate pKa values.

Item Type:	Refereed Article
Research Division:	Chemical Sciences
Research Group:	Organic Chemistry
Research Field:	Physical Organic Chemistry
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Chemical Sciences
Author:	Magill, AM (Miss Alison Magill)
Author:	Cavell, KJ (Professor Kingsley Cavell)
Author:	Yates, BF (Professor Brian Yates)
ID Code:	31988
Year Published:	2004
Web of Science® Times Cited:	310
Deposited By:	Chemistry
Deposited On:	2004-08-01
Last Modified:	2005-05-30
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