Formation and stability of organic zwitterions The carbon acid pKas of the trimethylsulfonium and tetramethylphosphonium cations in water
Keyword(s):
We report second-order rate constants of kDO = 7.5 × 104 and 9.9 × 105 (mol/L)1 s1 for exchange for deuterium of the first methyl proton of the trimethylsulfonium and tetramethylphosphonium cations, respectively, in D2O at 25 °C and I = 1.0 (KCl). The data were analyzed to give the following carbon acidities for these cationic carbon acids in water: (CH3)3S+, pKa = 28.5; (CH3)4P+, pKa = 29.4. These acidities are close to those of the neutral carbon acids acetonitrile and dimethylacetamide. This provides evidence that a portion of the stabilization of the cyanomethyl carbanion is due to resonance delocalization of negative charge from carbon to cyano nitrogen.Key words: carbon acids, carbanions, ylides, proton transfer.
1988 ◽
Vol 60
(02)
◽
pp. 247-250
◽
1999 ◽
Vol 64
(11)
◽
pp. 1770-1779
◽
Keyword(s):
1987 ◽
Vol 42
(9)
◽
pp. 1009-1013
◽
Keyword(s):
1998 ◽
Vol 269
(2)
◽
pp. 260-268
◽
Keyword(s):
Keyword(s):
1972 ◽
Vol 27
(9)
◽
pp. 1016-1020
◽
Keyword(s):
Keyword(s):
Keyword(s):