Svenson et al.
765
hydroxide (5 wt%) or sulfuric acid (5 wt%) to achieve a de-
sired final pH and mixed for one minute prior to injection of
an aqueous solution of the soluble model compound. Sam-
ples of the reaction were taken with a syringe through a rub-
ber septum. In the kinetic experiments sampling was done
every 15 s over the first few minutes, then at 2–5 min inter-
vals over the next 30–60 min. The reaction was monitored
until all of the model compound or chlorine dioxide was
consumed.
dimethylsulfone content was determined by GC using
cyclohexanol as an internal standard.
Reaction product characterization
3,4-Dimethoxyacetophenone (4)
1H NMR: d: 2.58 (s, 3H), 3.89 (s, 3H), 4.00 (s, 3H), 6.89
(d, 1H), 7.50 (d, 1H), 7.62 (m, 1H). MS m/z (%): 180 (M+,
46), 165 (100), 137 (9), 122 (8), 107 (5), 77 (12), 43 (9).
(2-Methyl-6-oxo-6H-pyran-3-ylidene) acetic acid methyl
ester (5)
Work-up procedures for the reaction mixtures
Organic compound concentrations were determined by
gas chromatography. Samples (20 L) of the reaction mix-
ture were quenched either by adding ascorbic acid (0.5 mL,
0.4 M) or a saturated aqueous sodium thiosulfate solution
(500 L). The quenched samples were extracted with
ethylacetate (0.5 mL) containing p-dibromobenzene or
biphenyl (0.6 mg L–1) as an internal standard. Thereafter, the
samples were dried over anhydrous sodium sulfate and made
up to 2 mL prior to GC analysis.
1H NMR d: 1.57 (d, 3H), 3.76 (s, 3H), 5.21 (m, 1H), 5.89
(m, 1H), 6.21 (m, 1H), 8.2 (m, 1H). MS m/z (%): 182 (M+,
1), 167 (8), 151 (7), 150 (8), 139 (57), 138 (79), 108 (43),
95 (17), 80 (24), 79 (47), 51 (46), 43 (100).
2-Methoxy-[1,4]-benzoquinone (6)
1H NMR: d: 3.56 (s, 3H), 5.71 (d, 1H), 6.78 (m, 2H). MS
m/z (%): 138 (M+, 44), 123 (8), 110 (33), 108 (47), 85 (27),
82 (28), 79 (13), 69 (100), 54 (42), 53 (43), 39 (23), 18 (17).
All compound analyses were carried out with a HP 5890
(splitless injection) instrument equipped with a flame ioniza-
tion detector, using He as the carrier gas. Injector and detec-
tor temperatures were 240 and 280°C, respectively.
Separations were achieved on a J&W DB-5 fused silica cap-
illary column (30 m × 0.32 mm × 0.25 m). Typical temper-
ature programs were from 45 to 250°C at a rate of
10°C min–1 with an initial time delay of 1 min, and from
100 to 270°C at 10–20°C min–1. In quantitative studies,
p-dibromobenzene or biphenyl was used as an internal stan-
dard and the relative peak areas and corresponding response
factors were used to calculate model-compound concentra-
tions.
4-Chloro-1,2-dimethoxy-benzene (7)
1H NMR d: 3.89 (s, 3H), 4.00 (s, 3H), 6.60 (d, 1H), 6.67
(d, 1H), 6.72 (m, 1H). MS m/z (%): 174 ([M + 2]+, 28), 172
(M+, 100), 159 (19), 157 (55), 129 (29), 111 (19), 107 (8),
93 (35), 79 (29), 65 (36), 51 (25), 43 (10).
1-(2-Chloro-4,5-dimethoxy-phenyl) ethanol (8)
1H NMR d: 1.47 (d, 3H), 3.76 (d, 6H), 4.68 (q, 1H), 6.51
(s, 1H), 6.58 (s, 1H). MS m/z (%): 218 ([M + 2]+, 14), 216
(M+, 51), 203 (35), 201 (100), 173 (19), 158 (12), 138 (81),
100 (9), 77 (22), 43 (54).
All GC–MS analyses were conducted as per GC analysis
on a HP 5985B GC–MS, equipped with a DB-5 capillary
column and using the same temperature program as per GC-
analysis. In the EI mode, the electron energy used was
70 eV.
1H NMR spectra were determined using a GE 300 MHz
instrument. Samples were dissolved in CDCl3. Chemical
shifts are given in ppm downfield from TMS (tetramethyl-
silane).
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© 2002 NRC Canada