however that the relative reactivity of 2- and 4-nitro-1-chloro-
benzenes is similar to that in normal nitronium ion nitration,
which gives an indication that in the reaction the activated site
may provide an incipient nitronium ion for reaction. There is no
reason to suppose the reaction is radical in character.
and then analysed by GC. The total time from taking a sample
to quenching was typically 60 seconds.
The nitrations of 2- and 4-nitro-1-chlorobenzenes in the presence
of zeolite
The procedure was similar except that in most cases samples
(ca. 0.5 cm ) were taken by syringe and quenched immediately
3
Experimental
Materials
by injection into saturated sodium hydrogen carbonate solution
3
3
(
20 cm ) with dichloromethane (2 cm ) through a subaseal
Dichloromethane was dried by distillation in silanised vessels
into containers in the glove box. The organic layers were
subsequently separated and analysed by GC. The products
from the nitration of 1-chloro-2-nitrobenzene were 1-chloro-
2,4- and -2,6-dinitrobenzene and these were analysed together
being insufficiently separated on GC. Separate NMR investig-
ation revealed that in all cases the 2,4- to 2,6-ratio exceeded
20:1. It was not more precisely determined.
Where either nitric acid or 1-chloro-2,4-dinitrobenzene were
added, these were introduced 10 minutes after addition of
dinitrogen pentoxide. Stirring was maintained for a further 10
minutes before addition of the substrate.
8
from calcium hydride. Dinitrogen pentoxide and anhydrous
9
nitric acid were prepared as described. 1-Chloro-2-nitro-
benzene, 1-chloro-4-nitrobenzene, 1-chloro-2,4-dinitrobenzene,
3
,5-dichloro-1-nitrobenzene, 2-nitrotoluene, 2,4-dinitrotoluene,
and 2,6-dinitrotoluene were used without further purification.
Zeolites H-ZSM-5, H-Faujasite 720, and H-Faujasite 780
had SiO /Al O ratios of 1000, 30, and 80 respectively and
2
2
3
were obtained from Zeolyst International. H-Mordenite and
Na-Faujasite had SiO /Al O ratios of 2.5 and 9 respectively
2
2
3
and were obtained from LaPorte Inorganics.
Drying zeolites
The nitration of 1-chloro-2-nitrobenzene by mixed acid
3
In all cases zeolites were dried before use by the following
procedure: the zeolite (ca. 0.5 g) was put into a glass boat inside
a tube attached to vacuum (<0.01 mmHg). This assembly was
heated steadily to 350 ЊC using a tube furnace. This temperature
was maintained (± 10 ЊC) for one hour, then the zeolite was
allowed to cool steadily, still under vacuum. When the zeolite
had reached room temperature, the system was sealed under
vacuum and the tube containing the zeolite was transferred to
the dry glove box, ready to use.
Sulfuric acid (100 cm , specific gravity 1.84) was poured into a
3
3
round bottom flask (250 cm ) and stirred. Nitric acid (10 cm ,
70%) was added carefully and a calcium chloride guard tube
was fitted. To this mixture at room temperature was added 1-
chloro-2-nitrobenzene (0.115 g, 0.727 mmol) in acetonitrile
(5 cm ). After 3 hours the mixture was quenched in ice–water
(ca. 500 cm ). The products were extracted with dichloro-
methane (4 × 10 cm ) and combined before being treated with
sodium hydrogen carbonate solution (30 cm , saturated solu-
tion) and separated; then with water (20 cm ) and separated.
3
3
3
3
3
GC conditions and response factors
Dichloromethane was removed from the organic layer and the
residue dissolved in deuterated chloroform and analysed by
H NMR (300 MHz).
The Pye Unicam PU4500 chromatograph was fitted with a
PU4700 autojector. The column was 7 foot long, packed with
Dexsil 400 (10%). Each sample was analysed 4 times. The nitro-
1
3
Ϫ1
gen flow rate was 40 cm min ; injection port was at 230 ЊC,
column was at 200 ЊC; detector was at 250 ЊC. The internal
standard used throughout was 3,5-dichloronitrobenzene.
Compounds (retention times/minutes, response factors) were
as follows: 3,5-dichloro-1-nitrobenzene (3.8, 1), 2-nitrotoluene
Acknowledgements
We thank the Defence Evaluation and Research Agency for
support, and Zeolyst International, Inc for the gift of samples
of zeolites.
(
(
2.2, 1.163), 2,4-dinitrotoluene (9.2, 1.014), 2,6-dinitrotoluene
6.2, 1.065), 1-chloro-2-nitrobenzene (3.1, 0.978), 1-chloro-4-
References
nitrobenzene (3.0, 0.902), 1-chloro-2,4-dinitrobenzene (9.8,
.859), 1-chloro-2,6-dinitrobenzene (10.1, 0.824).
1
2
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In a dry glove box, dried zeolite (0.05 g) and a magnetic
follower were put into the jacketed reaction vessel, through the
jacket of which was pumped cooling fluid from an external
thermostat. Dinitrogen pentoxide (0.1 g, 1 mmol) in dichloro-
4
3
methane (5 cm ) was added and stirred. After 10 minutes,
a solution of 2-nitrotoluene (0.11 g, 0.802 mmol) and 3,5-
dichloro-1-nitrobenzene (0.04 g, 0.208 mmol, GC reference
7
8
3
standard) in dichloromethane (1 cm ) was added.
1315.
3
Samples (ca. 0.5 cm ) were taken by pipette, put into a sample
9 K. A. Hylands and R. B. Moodie, J. Chem. Soc., Perkin Trans. 2,
996, 2073.
1
tube and then removed from the glove box before quenching
3
into saturated sodium hydrogen carbonate solution (20 cm )
3
with dichloromethane (2 cm ). The organic layer was separated
Paper 9/05118J
1
818
J. Chem. Soc., Perkin Trans. 2, 1999, 1815–1818