Molecular rearrangement. 36. Selective α-CH oxidation of alkylarenes by nitrogen dioxide on thermolysis with nitramines

Article abstract of DOI:10.1021/jo040176+

Thermolysis of 2,4,6-trichloro-N-nitroaniline 1 and N-methyl-2,4-dinitro-N- nitroaniline 2 each with primaryl alkylbenzenes led to the formation of acylbenzenes. Similar reactions with secondary alkylbenzenes afforded a mixture of acetophenone and aliphatic aldehydes. Use of tert-butylbenzene in this reaction yielded formaldehyde and 2,3-diphenyl-2,3-dimethylbutane. The mechanisms of the studied reactions are discussed.

Full text of DOI:10.1021/jo040176+

Molecu la r Rea r r a n gem en t. 36. Selective r-CH Oxid a tion of
Alk yla r en es by Nitr ogen Dioxid e on Th er m olysis w ith Nitr a m in es
Mahmoud Z. A. Badr
Chemistry Department, Faculty of Science, Assiut University, Assiut, Egypt
m.z.badr@acc.aun.edu.eg
Received April 16, 2004
Thermolysis of 2,4,6-trichloro-N-nitroaniline 1 and N-methyl-2,4-dinitro-N-nitroaniline 2 each with
primaryl alkylbenzenes led to the formation of acylbenzenes. Similar reactions with secondary
alkylbenzenes afforded a mixture of acetophenone and aliphatic aldehydes. Use of tert-butylbenzene
in this reaction yielded formaldehyde and 2,3-diphenyl-2,3-dimethylbutane. The mechanisms of
the studied reactions are discussed.
In tr od u ction
formaldehyde together with nitrogen and nitric oxide
gases. Thermolysis of the N-methyl-2,4-dinitro-N-nitro-
aniline 2 with N,N-diethylaniline yielded N-ethylaniline,
N-methyl-2,4-dinitroaniline, acetaldehyde, and nitric
oxide. The formation of these products may result via
A literature search reveals that photooxidation of
various organic compounds with nitrogen dioxide has
attracted the interest of several research groups. For
example, photolysis of N,N-dimethylaniline with nitrogen
dioxide was reported to result in photooxidative dealky-
lation and the formation of N-methylformanilide. Alco-
hols were also reported to undergo photooxidation when
photolyzed with nitro compounds. Furthermore, photo-
homolysis of the N-N bond in arylamino and nitrogen
7-9
dioxide radical pairs
which lead to oxidation of the
1
molecules in the medium.
In an earlier paper, it was indicated that production
of carbonyl compounds upon thermolysis of N-alkyl-N-
nitroanilines, proceeds through the intermediate N-
arylimine which suffered hydrolysis on workup or by
2
excited nitro compounds caused R-carbon oxidation of
N-alkylarylamines into the respective N-formanilide and
other oxidiation products.4 The rate of abstraction of
hydrogen from hydrocarbons with nitrogen dioxide was
water byproduct in the course of reaction to produce
parent aniline and aldehyde.7
3
also reported. In addition, dialkyl sulfide and dialkyl
As in the present studied reactions no water was
produced, it is not unreasonable to suggest that nitrogen
dioxide radicals oxidize selectively on the N-alkyl or alkyl
groups of the arene systems to afford the carbonyl
compounds produced.
disulfides were reported to undergo photooxidation upon
photolysis with nitrogen dioxide in air to yield the
respective sulfoxides.5 Photooxidation of alkanes with
nitrogen dioxide resulted in â-oxidation and formation
of aldehydes and ketones.6
Here, we report the results of the study of thermolysis
of primary, secondary, and tertiary alkylbenzenes with
N-nitroarylamines. The main objective of such a study
is to shed some light on the mechanism of thermal
oxidation of alkylbenzenes and to elucidate the effect of
structure on it.
The carbonyl compounds formed by thermolysis of both
of N,N-dimethyl- and N,N-diethylanilines with N-nitroa-
nilines must follow a pathway different from that re-
7
ported before. Both the aryl amino and nitrogen dioxide
radicals as oxidative species abstract R-hydrogen from
N,N-dialkylaniline to give N-alkyl-N-arylalkyl radical,
which couple with nitrogen dioxide to give the intermedi-
ate aryl-N-R-nitroalkane. The latter isomerize to the
respective alkyl nitrite.1
0-13
Resu lts a n d Discu ssion
Alternatively, coupling of the R-alkyl radical with
nitrogen dioxide may give directly the R-alkylnitrite
Thermolysis of 2,4,6-trichloro-N-nitroaniline 1 with
N,N-dimethylaniline gave a mixture of 2,4,6-trichloroa-
niline, N-methyl-N-nitrosoaniline, N-methylaniline, and
(7) Barnes, J .; Hickinbottom, W. J . J . Chem. Soc. 1961, 2616; Naud,
D. L.; J . Chem. Soc., Perkin Trans. 2 1996, 1321.
(
8) (a) Badr, M. Z. A. J . Photochem. Photobiol. 2004, 132, 163. (b)
(
1) D o¨ pp, D.; Heufer, J . Tetrahedron Lett. 1982 33, 1553. Dopp, D.;
Gowenlock, B. B.; Pfab, J .; Young, V. M. J . Chem. Soc., Perkin Trans.
2 1997, 915. (c) Naud, D. L.; Brower, K. R. J . Org. Chem. 1992, 57,
3303.
Heufer, J . J . Photochem. 1986, 32, 243.
(2) Rees, Y.; Williams, G. H. Adv. Free Radical Chem. 1969, 3, 199.
(
3) Denisov, E. T.; Derisova, T. G.; Geletii, V. Yu.; Balavouane, J .
(9) Solovskii, D. Catal. Rev. Sci. Eng. 1990, 32, 1. Cavani, F. C.;
Trifiro, F. Stnd. Sci. Catal. 1997, 110, 19.
(10) Dewar, M. J . S.; Ritchie, J . P. J . Org. Chem. 1985, 50, 1031.
(11) Saito, I.; Takami, M.; Matsuura, T. Tetrahedron Lett. 1975,
36, 3155.
(12) Ioki, Y. J . Chem. Soc., Perkin Trans. 2 1977, 1240.
(13) Chapman, O. L.; Cleveland, P. G.; Hoganson, E. D. J . Chem.
Soc., Chem. Commun. 1966, 101.
Kinet. Catal. 1998, 39 (2), 312.
4) Takami, M.; Matsuura, T.; Saito, I. Tetrahedron Lett. 1974, (8),
61.
5) Martinez, E.; Albuladejo, J .; J imenez, E.; Notario, A.; Aranda,
A. Chem. Phys. Lett. 1999, 308, 37.
6) Otsuka, K.; Takahashi, R.; Yamanaka, I. J . Catal. 1999, 185,
82.
(
6
(
(
1
1
0.1021/jo040176+ CCC: $27.50 © 2004 American Chemical Society
Published on Web 09/08/2004
6
706
J . Org. Chem. 2004, 69, 6706-6710

Selective R-CH Oxidation of Alkylarenes
SCHEME 1
SCHEME 2
troaniline, formaldehyde, and nitric oxide. Thermolysis
of the N-nitroaniline 2 with mesitylene gave 3,5-dimeth-
ylbenzaldehyde, N-methyl-2,4-dinitroaniline, formalde-
hyde, nitrogen dioxide, and nitric oxide. In these cases,
2
the N-nitroamines underwent N-NO homolysis to give
the respective radicals which affect oxidative hydrogen
abstraction from methyl group of the methyl arene to
yield the corresponding benzyl radical. The latter couples
in a consecutive step with nitrogen dioxide to give the
R-arylmethylnitrite,7
,9,16
which undergoes fission into
nitric oxide and arylalkoxy radicals. Disposition of the
latter afforded the aryladehyde.17
An alternative pathway involving one step cyclic
elimination8b of the aralkyl nitrite that results in â-scis-
sion leading to the corresponding arylaldehyde nitrous
acid, N-alkylaniline, and nitric oxide10 (Scheme 1).
The formation of formaldehyde in the above thermoly-
sis may result from the N-methylnitroaniline byproduct
through process of hydrogen abstraction, coupling of the
aryl-N-R-methyl radical with nitrogen dioxide, and fission
of the nitrite product followed by â-scission of N-methoxy
radical to yield formaldehyde and the arylamino radical
SCHEME 3
(Scheme 1).
Next, thermolysis of the N-nitroaniline 1 with tetralin
was examined. In our hands, the reaction grave R-tetral-
one, 2,4,6-trichloroaniline, and nitrogen gas. Similarly,
heating of 2 with ethylbenzene, p-ethyltoluene, n-propyl-
benzene, n-butylbenzene, and isobutylbenzene, respec-
tively, afforded the respective acylarenes together with
N-methyl-2,4-dinitroaniline, nitric oxide, and nitrogen
dioxide (Scheme 2).
which suffers O-N bond homolysis to yield the corre-
1
4
sponding N-alkoxy and nitric oxide radicals. The N-R-
alkoxy radical suffers â-scission1
4,15
into aldehyde (form-
aldehyde, acetaldehyde) and the N-arylamino radical,
which then abstracts hydrogen to produce the arylamine,
These results indicate that nitrogen dioxide radical
abstracts hydrogen selectively from the R-carbon atom
bonded to the benzene ring to generate highly resonance
stabilized substituted R-benzy radical which couple with
nitrogen dioxide to generate R-alkylnitrite. The R-alky-
(Scheme 1).
On the other hand, thermolysis of the N-nitroaniline
2
with p-xylene gave p-tolualdehyde, N-methyl-2,4-dini-
SCHEME 4
J . Org. Chem, Vol. 69, No. 20, 2004 6707

Badr
TABLE 1. Th er m olysis of th e 2,4,6-Tr ich lor o-N-n itr oa n ilin e 1 w ith Alk yla r en es (% Yield )
nitramine
(
mol/T (°C)/
time (h))
2,4,6-trichloro-
aniline (%)
alkylarene
carbonyl product
byproduct
gases
residue
e
tetralin (50 mL)
0.02/140/3
0.02/135/1
R-tetralone (20%)
75
72
N2
oil residue +
alkylarene
tar + alkyl-
arene
N,N-dimethylaniline
formaldehyde
N-methyl- N-nitroso-
aniline (20%) +
N-methylaniline
N2
a
(20 mL)
dodecane (20 mL)
0.01/180/1
81
20
2,4,6-trichloro-
phenol +
N2
(0.50 mol)
tar + alkane
b
2
(
-nitrododecane
5%)c
in silica gel (12 g)
0.01/140/2
2,6-dichloro-4-
N2O
red tar
nitroanilined
a
25
20
nD
1
N-methyl-N-nitrosoaniline: colorless oil, bp 130 °C/12 Torr;
1.5769; H NMR (CDCl3) δ 3.25 (s, 3H, CH3), 7.5-7.8 (m, CH, ArH).
1
b
26
-1
2
,4,6-Trichlorophenol: mp 66 °C (EtOH); IR (cm ) 3570 (OH, shifted in D2O); H NMR (CDCl3) δ 4.8 (s, 1H, OH), 6.8-7.3 (d, 2H,
ArH); MS m/z 196 (M 1, 100), 198 (M+1, 89). 2-Nitrododecane:27 bp 120 °C/1.4Torr; 1.4407; IR (film) (cm ) 1580-1365 (NO2); H NMR
-
c
20
nD
-1
1
d
28
(
CDCl3) δ 1.18 (t, 3H, CH3CH2), 1.51 (d, 3H, CH3-CH), 4.48 (q, 1H, CH), 1.40-1.62 (m, 18H, 9CH2). 2,6-Dichloro-4-nitroaniline: yellow
-
1
1
+
crystals; mp 194 °C (EtOH); IR (cm ) 3790, 3350 (NH2); H NMR (DMSO) δ 2.8 (s, 2H, NH2), 6.9-7.2 (2H, ArH); MS m/z 207 (M , 100).
e
20
nD
-1
1
R-Tetralone: bp 116 °C/6 Torr;
1.5685; IR (cm ) 1680 (CdO); H NMR (CDCl3) δ 2.1, 2.5, 2.9 (t, 3CH2), 7.2-7.9 (m, 4H, ArH).
TABLE 2. Th er m olysis P r od u ct of th e N-Meth yl-2,4-d in itr o-N-n itr oa n ilin e 2 w ith Alk yla r en es
nitramine
2,4- dinitro-
aniline
(% yield)
(mol/T (°C)
carbonyl product
(% yield)
byproduct
(% yield)
alkylarene
p-xylene
/time (h))
gases
residue
a
formaldehydeb
formaldehyde
+
0.02/140/2 p-tolualdehyde (18)
78
95
NO2 , NO
NO2 , NO
tar + arene
tar + arene
+
mesitylene
0.03/170/4 2,5-dimethylbenz-
aldehyde (20)
0.03/140/4 acetophenone (18)
c
d
+
ethylbenzene
p-ethyltoluene
82
85
NO2 , NO
NO2 , NO
tar + arene
tar + arene
+
0.02/160/2 p-methylaceto-
e
phenone (22)
f
+
N,N-diethylaniline 0.02/135/2 acetaldehyde (18)
78
N-ethylaniline (23)
formaldehyde
NO2 , NO
tar +
(DMA)
DMA (10%)
tar + arene
tar + arene
tar + arene
tar + arene
tar + arene
tar + arene
g
+
n-propylbenzene
isoproylbenzene
n-butylbenzene
isobutylbenzene
sec-butylbenzene
tert-butylbenzene
dodecane (50 mL)
0.02/140/4 propiophenone (20)
80
82
79
76
80
79
81
NO2 , NO
NO2 , NO
NO2 , NO
NO2 , NO
NO2 , NO
NO2 , NO
d
+
0.03/140/2 acetophenone (18)
0.02/140/2 n-butyrophenone (21)
0.02/140/3 isobutyrophenone (20)
0.02/140/2 acetophenone (19)
h
+
i
+
d
+
formaldehyde
b
k
+
0.03/140/2 formaldehyde
bicumyl (14)
j
l
0.04/150/2 paraformaldehyde
m-dinitrobenzene (5) + N2, 0.24 mol (73%) tar + alkane
(0.5)
2-nitrododecane (5)m
+ NO (12%)
a
29
b
2
,4-Dinitrophenyl hydrozone (2,4-DNPH), orange-red crystals (benzene), mp 243 °C.
2,4-DNPH (petroleum ether), mp 167 °C,
3
0
c
31
d
30 e
semicarbzone, mp 168 °C.
mp 259 °C.
,4-DNPH, orange crystals (EtOH), mp 163 °C.
mp 167 °C, semicarbazone (petroleum ether), mp 189 °C. 2,3-Dimethyl-2,3-diphenylbutane (bicumyl), white needles (EtOH), mp
15 °C, MS m/z ) 238 (M ), H NMR (CDCl3) δ 1.28 (s, 12H, 4CH3), 7.3-7.8 (m, 10H, ArH). Anal. Calcd for C18H22: C, 90.75; H, 9.25.
Found: C, 90.66; H, 9.30. m-Dinitrobenzene, mp 92 °C (EtOH).
Semicarbazone (EtOH), mp 218 °C.
2,4- DNPH (EtOH), mp 249 °C.
2,4- DNPH, red crystals (EtOH), mp 192 °C.
Paraformaldehyde, white powder, mp 123 °C; 2,4-DNPhH, prisms (petroleum ether),
2,4-DNPH, red crystals (EtOH),
2,4- DNPH (EtOH), mp 192 °C.
3
0
f
30
g
30
h
30,32
2,4- DNPH (EtOH), mp 162 °C.
i
33 j
2
3
0
k
34
+
1
1
l
35
m
20
2-Nitrododecane, bp 120 °C/ 1.4 Torr, nD 1.4407. Anal. Calcd for
C12H25NO2: C, 66.97; H, 11.62; N, 6.51. Found: C, 70.01; H, 11.79; N, 6.46. 2-Nitrododecane + MeOH-KOH 10% + H2O2 (in excess)
2
0
heated at 70 °C for 6 h, collected, mixture extracted with (petroleum ether) to separate 2-dodecanone: bp 100 °C/2.5 Torr, n 1.4332;
D
3
6
semicarbazone (EtOH), mp 124 °C.
SCHEME 5
lnitrite undergoes elimination of HNO molecule to pro-
duce the corresponding carbonyl compound10 (Scheme 3,
route a).
An alternative multistep unimolecular dissociation of
the alkylnitrite and disposition of the intermediate
radicals3 into the aryl alkyl ketone can also be suggested
,8
(route b, Scheme 3).
Thermolysis of N-nitroaniline 2 with isopropylbenzene
and sec-butylbenzene yielded formaldehyde and acetal-
dehyde, respectively, together with acetophenone as
byproduct in both cases. The formation of such products
can be rationalized by the mechanistic pathway depicted
in Scheme 4.
Finally, thermolysis of N-nitroaniline 2 with tert-
butylbenzene was studied. In this case, the reaction gave
2,3-dimethyl-2,3-diphenylbutane (bicumyl), N-methyl-
(14) Furlan, A. Chem. Phys. Lett. 1999, 309, 157. Effrenhauser, C.
S.; Feder, P.; Huber, J . R. J . Phys. Chem. 1990, 94, 296. Untch, A.;
Schinke, R.; Cotting, R.; Huber, J . R. J . Chem. Phys. 1993, 99, 9553.
(15) Wang, J .; Brower, K. R. J . Org. Chem. 1997, 62, 9048.
(16) Grossi, L.; Strazzai, S. J . Org. Chem. 1999, 64, 8076.
(17) Iyima, S.; Yudasaka, M.; Yamada, R.; Bandaw, S.; Suenaga,
S.; Kokai, F.; Takahashi, K. Chem. Phys. Lett. 1999, 309, 165.
6
708 J . Org. Chem., Vol. 69, No. 20, 2004

Selective R-CH Oxidation of Alkylarenes
SCHEME 6
SCHEME 7
2
,4-dinitroaniline, formaldehyde, nitrogen dioxide, and
nitric oxide. Since tert-butylbenzene has no R-CH, the
most plausible rationalization for the products formation
is by hydrogen abstraction from â-CH to separate the
3
R,R-dimethyl benzyl-R-methyl radical, which couples with
nitrogen dioxide to generate the R-methylnitrite. The
latter undergo O-NO bond fission into primary â-alkoxy
radical and nitric oxide. The alkoxy radical suffer â-scis-
sion to generate formaldehyde and the highly stabilized
tertiary cumyl radical,18 which dimerize to bicumyl, as
depicted in Scheme 5.
To study and determine the quantity of gases evolved
during the thermolysis of N-nitroanilines a control
experiment was performed where the N-nitroaniline 1
is heated in dodecane to give the products 2,4,6-trichlo-
roaniline, 2,4,6-trichlorophenol, and 2-nitrododecane, and
the gas evolved was collected and analyzed quantitatively
by GLC and identified to be only nitrogen up to 0.50%
mol.
SCHEME 8
Similarly, thermolysis of N-nitroaniline 2 in dodecane
gave paraformaldehyde (white sublimate at condenser
wall), N-methyl-2,4-dinitroaniline, and m-dinitrobenzene,
and the gases collected were analyzed quantitatively by
GLC and were identified to be nitrogen (75%) and nitric
oxide (12%).
Paraformaldehyde is suggested to be formed from the
N-methyl group of the N-nitroaniline 2, which suffers
abstraction of hydrogen to give the aryl N-methyl radical
which couples with nitrogen dioxide into N-methylnitrite.
The latter undergoes fission into nitric oxide and N-
methoxy radical, which undergoes â-scission into N-
anilino radical and formaldehyde. Polymerization of the
latter forms paraformaldehyde.
of the nitrate radical goes through coupling with alkyl
or aryl radicals followed by fission (Scheme 6).
Production of 1,3-dinitrobenzene on heating the N-
nitroaniline 2 in dodecane seems to be generated from
the aryl radical (Scheme 6), which abstracts hydrogen
to produce the m-dinitrobenzene.
Also, production of 2,4,6-trichlorophenol from heating
the N-nitroaniline 1 in dodecane can be rationalized as
shown in Scheme 7.
Formation of formaldehyde and N-methyl-N-nitrosoa-
niline from thermolysis of the N-nitroaniline 1 with N,N-
dimethylaniline can be rationalized23 as depicted in
Scheme 8.
Formation of nitrogen can be rationalized in terms of
the formation of the intermediate N-nitro-N-nitrsoalkane
(
or arene) which rearranges to the corresponding (aryl)-
1
9,20
alkyldiazonium nitrate.
The diazo compound under-
On the other hand, heating N-nitroaniline 1 alone, in
the absence of oxidizable species, on silica gel gave 2,4,6-
trichloroaniline, 2,6-dichloro-4-nitroaniline, and nitrogen
dioxide. Formation of dichloronitroaniline can be ratio-
goes homolysis to alkyl and nitrate radicals and nitrogen
(Scheme 6).
An alternative pathway involves coupling of the N-
nitro-N-arylamino radical with nitric oxide to generate
aryl-N-nitroso-N-nitrite, which rearranges to aryldiazo-
nium nitrate, which then undergoes homolysis into aryl
8
a,24
nalized to result via an ipso-substitution reaction
of
the 4-chloro substituent by the nitrogen dioxide radical
2
1,22
and nitrate radicals and nitrogen
(Scheme 6). The fate
(
(
22) Bolsman, T. A. B.; Deboer, T. H. J . Tetrahedron 1973, 29, 3579.
23) Chow, Y. L.; Richard, H.; Snyder, R. W.; Lockhart, R. W. Can.
(
18) Tanko, J . M.; Pacut, R. J . Org. Chem. 2001, 123, 5703. Gould,
J . Chem. 1979, 57, 2936.
I. R.; Baretz, B. H.; Turro, N. J . J . Phys. Chem. 1987, 91, 925. Gould,
I. R.; Zimmit, M. B.; Turro, N. J .; Baretz, B. H.; Lehr, G. F. J . Am.
Chem. Soc. 1985, 107 , 4607.
(24) Pryor, W. A.; Echols, Y. T., J r.; Smith, K. J . Am. Chem. Soc.
1966, 88, 1189. Ito, R.; Migita, T.; Morikawa, N.; Simmura, O.
Tetrahedron 1965, 21, 955. Ivanora, G. M.; Voronova, L. K.; Deryagina,
E. N.; Voronkov, M. G. Zh. Org. Khim. 1979, 15 , 1232. Voronkov, M.
G.; Deryagina, E. N.; Ivanova, G. M. Zh. Org. Khim. 1976, 12, 2179.
Voronkov, M. G.; Deryagina, E. N.; Klochkova, L. G.; Ivanova, G. M.
Zh. Org. Khim. 1977, 13, 2575.
(
(
19) Donaruma, L. G.; Carmady, D. J . J . Org. Chem. 1957, 22, 635.
20) Forrest, D.; Gowenlock, B. G.; Pfab, J . J . Chem. Soc., Perkin
Trans. 2 1979, 576.
21) Gowenlock, B. G.; Kresze, G.; Pfab, J . Tetrahedron 1973, 29,
(
3
2
587; Brian, D. F.; Gowenlock, G.; Pfab, J . J . Chem. Soc., Perkin Trans.
1979, 576.
(25) Hartman, W. W.; Roll, L. Organic Syntheses; Wiley: New York,
1943; Collect. Vol. II, p 341.
J . Org. Chem, Vol. 69, No. 20, 2004 6709

Badr
SCHEME 9
were heated together under nitrogen atmosphere in the dark.
The gases evolved were collected from the outlet into cold
traps, ethanol-carbon dioxide, and liquid nitrogen succes-
sively, where nitrogen, nitric oxide, and nitrogen dioxide were
analyzed by GC. Formaldehyde was passed through the
hydrazine solution to produce the corresponding hydrazone.
The dark mixture was steam distilled and part of the aqueous
distilled treated with dinitrophenylhydrozine to precipitate the
hydrazones of the carbonyl products. Extraction of water
extract with ether may separate some of the arylamine
products. Fractionation of the nonaqueous distillate and
separation of the excess arenes gave the corresponding aral-
dehyde or alkylaryl ketones. Extraction of the nonresolvable
resides with glacial acetic acid and evaporation separated the
corresponding arylamine product. Products of the N-nitroa-
niline 1 on heating with silica gel were separated and analyzed
as above. All products were quantitatively analyzed by GC-
MS using reference compounds as internal standards and by
GLC by comparison of their retention times with those of
known concentrations of authentic samples and by their mass
spectra.
through formation of cyclohexadienyl radical intermedi-
ate (A) followed by elimination of chlorine atom as
depicted in Scheme 9.
Exp er im en ta l Section
Melting points were obtained with a hot-stage apparatus
calibrated with known samples. Column chromatography and
TLC were carried out using silica gel (80-120 mesh) or Merck
Kieselgel 60. All products were identified by elemental analy-
sis, TLC, IR, H NMR, MS, and mixed melting point with
authentic samples wherever possible and are summarized in
Tables 1 and 2.
1
Th er m olysis of th e N-Nitr oa n ilin es in Dod eca n e. The
N-nitroaniline and dodecane were heated together under a
nitrogen atmosphere in the dark. The gases evolved were
collected in cold traps, with ethanol-carbon dioxide and liquid
nitrogen successively, where nitrogen and nitric oxide or
nitrogen dioxide were quantitatively analyzed by gas chroma-
tography. Formaldehyde was changed into the corresponding
hydrazone. Praformaldehyde accumulated in the condenser on
N-nitroaniline 2 thermolysis was collected and identified by
hydrazone formation. The pyrolysis products were extracted
with ether, which was extracted with sodium carbonate
solution to extract phenolic products, and ether was evaporated
and the oil residue fractionally distilled at reduced pressure
to collect dodecane, trichlorophenol, trichloroaniline, and 1,3-
dinitrobenzene. The oily residue was fractionated into dode-
cane and 2-nitrododecane, and the black residues were ex-
tracted with petroleum ethers to separate 2,4,6-trichloroaniline
and N-methyl-2-4-dinitroanilines. All products were quanti-
tatively analyzed by GC-MS and or by GLC.
Ch em ica l Com p ou n d s. Unless otherwise stated, the ma-
terials for synthesis and comparisons were used as com-
mercially available: alkylarenes, alkanals, alkanones, aryla-
lkylkanones, N,N-diethylaniline, N,N-dimethylaniline, N-ethyl-
aniline, N-methylaniline, 2,6-dichloro-4-nitroaniline, 1,3-dini-
trobenzene, 2,4,6-trichlorophenol, 2,4,6-trichloroaniline, 2,6-
dichloro-4-nitrophenol. Other chemicals used or produced in
the study are identified and analyzed as in Tables 1 and 2.
8
a
2
,4,6-Tr ich lor o-N-n itr oa n ilin e: white needles (petro-
leum ether); mp 134 °C.
8
a
N-Meth yl-2,4-d in itr o-N-n itr oa n ilin e: yellow crystals
EtOH); mp 115 °C.
(
Th er m olysis of th e N-Nitr oa n ilin es in Ar en e Solven ts.
The N-nitroaniline (0.01-0.02 mol) and the arene (20 mL)
(
(
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(
(
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(
26) Strubell, W. J . Prakt. Chem. 1961, 14, 174.
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Ack n ow led gm en t. This work was carried out with
the financial support of the International bank. Part of
this work was carried out at Boston College, Boston,
MA.
Shipiro, I. O.; Nir, M.; Hoffmann, R. E.; Rabinovitz, M. J . Chem. Soc.,
Perkin Trans. 2 1994, 1519.
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