1370
Can. J. Chem. Vol. 83, 2005
spectroscopic data such as IR and NMR spectra. Other mate-
rials were of the highest quality available and were generally
recrystallized before use. Glass-distilled water was further
boiled and cooled under nitrogen just before use.
References
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Kinet. 5, 1 (1973).
Kinetics
Kinetic studies were performed using a Scinco S-3100
2. H. Morales-Rojas and R.A. Moss. Chem. Rev. 102, 2497
(2002).
PDA UV–vis spectrophotometer for slow reactions (t1/2
≥
10 s) or an Applied Photophysics SX-17MV stopped-flow
spectrophotometer for fast reactions (t1/2 < 10 s) equipped
with a constant-temperature circulating bath. The reactions
were followed by monitoring the appearance of 4-nitro-
phenoxide (or 4-nitrothiophenoxide for the reaction of 2).
Each reaction was monitored up to 10 half-lives.
Typically, a reaction was initiated by adding 5 µL of a ca.
0.01 mol/L solution of substrates in MeCN by a gas-tight sy-
ringe to a 10 mm quartz UV cell containing 2.50 mL of a
thermostatted reaction mixture made of an aliquot of nucleo-
phile solution. The stock solutions (ca. 0.2 mol/L) of 4-ClPhO–,
Ox–, and HOO– were prepared by dissolving 2 equiv. of 4-
ClPhOH, OxH, and HOOH and 1 equiv. of standardized
NaOH solution to keep the pH constant by making self-
buffered solutions. However, owing to the low solubility of
4-ClPhSH in water, the concentration of 4-ClPhS– stock so-
lution was prepared by mixing ca. 0.011 mol/L of 4-ClPhSH
and 0.010 mol/L of NaOH. The kinetic conditions and re-
sults are summarized in the Supporting information.4 Other
detailed kinetic methods were reported previously (8b, 8c).
3. (a) J.S. Tsang, A.A. Neverov, and R.S. Brown. J. Am. Chem.
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Product analysis
One of the reaction products, 4-nitrophenoxide (or 4-
nitrothiophenoxide for the reactions of substrate 2), was de-
termined quantitatively by measuring the optical density us-
ing a UV–vis spectrophotometer in all cases. Other products
(e.g., S-4-chlorophenyl thioacetate, S-4-chlorophenyl thio-
benzoate, and 4-chlorophenyl dithiobenzoate for the
reactions of substrates 1–4 with 4-chlorothiophenoxide, re-
spectively) were analyzed by a GC technique. The quantita-
tive analysis was performed using the authentic samples by a
Varian 3800 Model GC with a DB 624 column (30 m ×
0.32 mm × 1.8 µm) for S-4-chlorophenyl acetate (retention
time 13.50 min at the injector temperature of 250 °C, the
column temperature starting at 50 °C and increased by
15 °C/min) and with a DB 5 column (30 m × 0.32 mm ×
0.25 µm) for S-4-chlorophenyl thiobenzoate and 4-
chlorophenyl dithiobenzoate (retention time 11.23 and
10.43 min, respectively, at the injector temperature of
250 °C, the column temperature starting at 50 °C and in-
creased by 20 °C/min).
9. (a) I.H. Um, Y.M. Park, and E. Buncel. Chem. Commun. 1917
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Acknowledgments
I.H.U. is grateful for the financial support from the Korea
Research Foundation (KRF-2002-070-C00061) and to Sang-
Eun Jeon for analysis of the reaction products by GC. E.B.
thanks the Natural Sciences and Engineering Research
Council of Canada (NSERC) for a research grant. The au-
thors also acknowledge helpful discussions with Professors
J.M. Dust, S. Hoz, and J.F. King (29).
14. I.H. Um, J.S. Lee, and S.M. Yuk. J. Org. Chem. 63, 9152
(1998).
15. I.H. Um, E.J. Lee, J.A. Seok, and K.H. Kim. J. Org. Chem. 70,
7530 (2005).
16. D.J. Hupe and W.P. Jencks. J. Am. Chem. Soc. 99, 451 (1977).
17. W.J. Middleton, E.G. Howard, and W.H. Sharkey. J. Org.
Chem. 30, 1375 (1965).
© 2005 NRC Canada