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The effect of solvent on the -effect: the MeCN-H2O solvent system
Ik-Hwan Um, Young-Min Park, and Erwin Buncel†
Department of Chemistry, Ewha Womans University, Seoul 120-750, Korea
†Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
Tel: 613-533-2635. Fax: 613-533-6669. E-mail: buncele@chem.queensu.ca
Table 1. Summary of second-order rate constants for the reaction of p-nitrophenyl acetate
with butane-2,3-dione monoximate (Ox-) and p-chlorophenoxide (ClPhO-) in MeCN-H2O
mixtures at 25.0 ± oC.a
--------------------------------------------------------------------------------------------------mole % MeCN
kOx-, M-1s-1
kClPhO-, M-1s-1
kOx- / kClPhO---------------------------------------------------------------------------------------------------0
65.8 (65.8)b
0.685 (0.685)
96 (96)
10
37.2 (77.8)
0.385 (0.653)
97 (119)
20
29.5 (139)
0.255 (0.760)
116 (183)
30
29.2 (309)
0.197 (1.35)
148 (229)
40
35.6 (740)
0.198 (2.80)
180 (264)
50
45.6 (1,680)
0.217 (5.90)
210 (285)
60
67.5 (3,850)
0.266 (13.6)
254 (283)
70
122 (8,200)
0.391 (34.7)
312 (236)
80
263 (17,200)
0.712 (94.8)
369 (181)
90
1,070 (40,500)
2.12 (334)
505 (121)
--------------------------------------------------------------------------------------------------aThe uncertainty in the rate constants is estimated to be less than ±3 % based on replicate
runs.
bThe data in the parentheses are obtained from ref. 7c for the corresponding reaction run in
DMSO-H2O mixtures.