1010 J. Chin. Chem. Soc., Vol. 51, No. 5A, 2004
Wu et al.
1
CONCLUSION
intensity): 80 (M+2+, 14), 78 (M+, 41), 43 (100). H NMR
(CDCl3): 5.99-5.94 (m, 1H), 5.40-5.20 (m, 2H), 4.05 (CH2Cl)
< 4%. The deuterium purity of compound 8 was greater than
96%. GCMS: m/z (relative intensity): 94 (M+2+, 8), 92 (M+,
24), 57 (100). 1H NMR (CDCl3): 5.05 (s, 1H), 4.92 (s, 1H),
3.90 (CH2Cl) < 4%, 1.83 (s, 3H).
The values of the intramolecular and intermolecular
leaving groups effects are both greater than unity in the free
radical SH2¢ reactions, and the values of secondary a-deute-
rium kinetic isotope effects are 1.20 to 1.22. All data favor
the SH2¢ reactions to proceed with the concerted mechanism
rather than the stepwise mechanism. The magnitude of the
secondary a-deuterium kinetic isotope effect, in general, is a
measure of the nucleophile-leaving group distance in the SN2
reaction transition state. However, Westaway et al. pointed
out that the magnitude of the secondary a-deuterium kinetic
isotope effect was dependent upon the length of only the
shorter reacting bond if the SN2 transition state were unsym-
metrical. Therefore, the magnitude of the secondary a-deute-
rium kinetic isotope effect in an SH2¢ reaction might indicate
the looseness between the reaction center and the leaving
group in the transition state rather than the distance between
the alkyl radical and the leaving group.
General Procedure for Competitive Photostimulated Re-
actions of 2-Substitutedallyl Halides with t-Butylmercury
Chloride8
A pair of 2-substitutedallyl halides (1.0 mmol), t-
BuHgCl (0.1 mmol) and internal standard (0.05 mmol of
biphenyl) were dissolved in 1 mL of nitrogen-purged dry
dimethylsulfoxide. The solution was divided into dry and ni-
trogen-purged four quartz tubes (0.25 mL in each tube) each
equipped with a rubber septum. The tubes were irradiated at
35-40 °C with a 100 W UV lamp placed about 20 cm from the
reaction tubes. Reaction tubes were removed at various times
and the yields of the substitution products were determined
by Gas Chromatography. Identification of substitution prod-
ucts was confirmed by comparison of their GCMS data with
those of the authentic compounds synthesized by the method
described in our previous reports.8,11 GLC yields were deter-
mined by using an internal standard (biphenyl) and were cor-
rected with predetermined response factors. The relative rate
ratios of the competitive reactions are shown in Table 1.
EXPERIMENTAL SECTION
Analytical gas chromatography was performed using a
Perkin-Elmer Autosystem with a DB-5 column (0.25 mM, 60
M) and a flame ionization detector. 1H NMR spectra were re-
corded on a 300 MHz VXR FT-NMR spectrometer with tetra-
methylsilane as the internal standard. GCMS were recorded
on a Quattro GCMS 5022 spectrometer or HP 5890 Series II
Gas Chromatograph with HP 5972A MSD. Melting points
were determined on a Thomas-Hoover capillary melting
point apparatus and were uncorrected.
ACKNOWLEDGEMENT
This research was supported by a grant from the Na-
tional Science Council of the R.O.C. to Yuh-Wern Wu (NSC
88-2113-M-214-003).
Materials
Solvents were purchased from Riedel-de Haen and
Mallinckrodt. Dimethyl sulfoxide (DMSO) was distilled
from calcium hydride and stored over 4A molecular sieves
under nitrogen; diethyl ether, and tetrahydrofuran were dis-
tilled from sodium metal. Other solvents were purchased and
used without purification. Allyl chloride, 2-methylallyl chlo-
ride, allyl bromide, 2-methylallyl bromide, t-butyl chloride,
and biphenyl were purchased from Aldrich Chemical Com-
pany. In most cases, the reagents were used without further
purification. Organomercurials were synthesized by the stan-
dard Grignard procedure.19 3,3-d2-3-chloro-1-propene (7)20
and 3,3-d2-3-chloro-2-methyl-1-propene (8)21 were synthe-
sized by the methods reported in the literature. The 96% pure
deuterium of compound 7 was obtained. GCMS: m/z (relative
Received December 9, 2003.
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