A.B. McKague, D.R. Taylor / Chemosphere 45 .2001) 261±267
263
2.1.2. 3,4,5-Trichlorocatechol .5)
from hexane gave 15 as pale yellow crystals 030 g, 39%
yield), m.p. 63±64°C 0Lit. 64±65°C; Brown and McCall,
1955).
1 M Boron tribromide in CH2Cl2 048 ml, 0.048 mol)
was added over 10 min to a stirred solution of 4,5,6-
trichloroguaiacol 09.0 g, 0 04 mol) in dichloroethane 035
ml). The mixture was re¯uxed 4 h then cooled, water
added cautiously with stirring and the product extracted
with ether. The extracts were washed with water, dried
and concentrated to give the crude product 08 g).
Crystallization from toluene 025 ml) gave colourless
crystals of 5 06 g, 71% yield), m.p. 131±134°C 0Lit. 134±
135°C; Cousin, 1898).
2.1.6. 3,4,5-Trichloroguaiacol .8)
Three drops of H2SO4 were added to a stirred so-
lution of 4,5-dichloroguaiacol 0Fig. 6) 0Matell, 1955),
019.2 g, 0.1 mol) in acetic anhydride 050 ml). The so-
lution was stirred at 50°C for 1 h then cooled and
poured into cold water with stirring. After a few
minutes, the product was ®ltered and washed with
water giving 4,5-dichloroguaiacol acetate 023 g, 100 %
yield). m.p. 64±66°C. The dichloroacetate was dis-
solved in acetic acid 0140 ml) in a round bottom ¯ask
by warming to 40°C. A solution of chlorine 021 g,
0.3 mol) in acetic acid 0250 ml) was added, the ¯ask
stoppered and the solution stirred at 40±50°C for 6 h.
The product was cooled and poured into cold water
with stirring. Filtration gave crude 3,4,5-trichloro-
guaiacol acetate 023 g) which was crystallized from
hexane 070 ml) to give colourless needles 015 g, 56 %
yield), m.p. 69±70°C. The trichloroacetate was dis-
solved in methanol 0160 ml), 10% KOH in metha-
nol:water, 9:1 0160 ml) added and the solution stirred
at 50°C for 20 min. The product was cooled, water
0700 ml) added and acidi®ed with dilute hydrochloric
acid. After stirring for 20 min, ®ltration gave crude
3,4,5-trichloroguaiacol 8 011 g). Crystallization from
hexane 0120 ml) gave colourless needles of 8 010 g, 74%
2.1.3. 6-Chloroguaiacol .17)
Guaiacol 062 g, 0.5 mol) was dissolved in a solution
of NaOH 026 g, 0.65 mol) in water 0600 ml). Com-
mercial bleach 0700 ml, 0.5 mol) was added with stir-
ring over 20 min keeping the temperature below 25°C.
After stirring another 20 min, the solution was acidi®ed
with hydrochloric acid and the product extracted with
ether. The extracts were washed with water, dried and
concentrated to give the crude product 080 g). Frac-
tional distillation through a 10 cm Vigreux column
gave 6-chloroguaiacol 17 035 g) having 80% purity.
Crystallization from hexane gave colourless needles of
17, 030 g, 38% yield), m.p. 51±52°C 0Lit. 54°C; Brown
and McCall, 1955).
2.1.4. 3,4-Dichloroguaiacol .14)
A mixture of 3,4-dichlorocatechol 13 05.3 g, 0.03
mol), K2CO3 04.1 g, 0.03 mol) and methyl iodide 05.3 g,
0.04 mol) in acetone 050 ml) was re¯uxed 3 h with
stirring. The product was cooled and partitioned be-
tween 5% NaOH and ether. The aqueous layer was
acidi®ed and extracted with ether. The ether extracts
were washed with water, dried and concentrated to give
a yellow oil 04.5 g). Puri®cation on SiO2 0150 g) and
elution with hexane:ethyl acetate, 5:1, gave 3,4-dic-
hloroguaiacol 14 03.8 g) which was crystallized from
hexane to give colourless needles 03 g, 52% yield), m.p.
50±51°C.
yield), m.p. 85±86°C 0Lit. 81±83°C; Lindstrom and
Osterberg, 1980).
2.1.7. 3,4,6-Trichloroguaiacol .9)
Sulfuryl chloride 03.0 g, 0.022 mol) was added to a
solution of 3,4-dichloroguaiacol 14 03.8 g, 0.02 mol) in
acetic acid 040 ml) with stirring. The solution was stirred
1 h at 50°C then cooled and poured into cold water.
Filtration and crystallization from hexane containing a
little acetone gave pale yellow needles of 9 03.2 g, 71%
yield), m.p. 103±104°C 0Lit. 103±104°C; Knuutinen,
1984; Smith et al., 1994).
2.1.5. 4,6-Dichloroguaiacol .15)
4-Chloroguaiacol 0Fig. 7) 0Brown and McCall, 1955),
064 g, 0.4 mol) was dissolved in a solution of NaOH 020
g, 0.5 mol) in water 0500 ml). Commercial bleach 0500
ml, 0.36 mol) was added with stirring over 20 min
keeping the temperature below 25°C. After stirring an-
other 20 min, ether 0400 ml) was added and the mixture
acidi®ed with 10% hydrochloric acid. The ether layer
was separated and the aqueous layer extracted twice
more with ether. The ether extracts were combined,
washed with water, dried and concentrated to give the
crude product 070 g) as a dark oil. Partial puri®cation by
passing through SiO2 0400 g) and elution with hex-
ane:ether 4:1 01200 ml) gave 4,6-dichloroguaiacol 15 040
g) 90% purity. Trituration followed by crystallization
3. Results and discussion
Catechols and guaiacols are interconvertable by
limited methylation/demethylation 0Fig. 3). Mixtures
of isomeric guaiacols may be obtained from catechols
containing substituents R 0unless the symmetry of the
catechol is maintained by the presence of more then
one identical substituent in the appropriate positions,
e.g. 4,5-, 3,4,5,6-, etc). This is the basis of the previ-
ously reported preparation of 3,4-dichloroguaiacol 14
0Knuutinen and Tarhanen, 1981) and 3,4,5-trichloro-
8 0Lindstrom and Osterberg, 1980), two
guaiacol
chlorinated guaiacols of interest in the present study.