Nitrogen Dioxide

NO2
(NO2)

[10102-44-0]  · NO2  · Nitrogen Dioxide  · (MW 46.01) (N2O4)

[10544-72-6]  · N2O4  · Nitrogen Dioxide  · (MW 92.02)

(nitration of aromatic1,2 and unsaturated3,4 compounds; conversion of oximes into dinitromethanes;3,5,6 halogenation of arenes;7,8 oxidation of many functional groups.9-11)

Alternate Names: nitrogen tetroxide; dinitrogen tetroxide.

Physical Data: a reddish-brown gas above 21.15 °C and a brown or yellow-brown liquid below 21.15 °C; mp 11.2 °C; bp 21.15 °C; d204 1.448 g cm-3, d21.3(gas) 3.3 g L-1; exists as N2O4 in liquid and solid state; as a mixture of NO2 and N2O4 in the gas phase; and as NO2 above 135 °C.

Solubility: sol CCl4, CH2Cl2, DMF, ether, concd sulfuric and nitric acids.

Form Supplied in: brown liquid under pressure.

Preparative Methods: prepared by thermal decomposition of lead nitrate or from N2O5.12

Handling, Storage, and Precautions: deadly poison! One of the most insidious gases. 100 ppm is dangerous and 200 ppm may be fatal. Decomposes in water or alkaline solutions. Use in a fume hood.

Nitration of Aromatic Compounds.

Examples of arene nitration with nitrogen dioxide at high temperature or in the presence of concentrated acids are numerous, but they are often messy.1 In the best cases, mixtures of o- and p-nitro compounds are formed with predomination of the former (eq 1).13

Activated arenes and even porphyrins can be nitrated directly by nitrogen dioxide in benzene or dichloromethane solution.14,15 Phenols usually give di-o-nitro substituted compounds as well as 4-nitrocyclohexadienones (eq 2).

o-Nitrophenols have been obtained in high yield using pyridinium salts as NO2 transfer agents.16 Anthracene reacts with nitrogen dioxide to give cis- and trans-9,10-dinitro-9,10-dihydroanthracene.17 Compounds of lower reactivity than benzene can be nitrated by nitrogen dioxide in the presence of Ozone even at low temperatures.18,19 Thus, treatment of acetanilides with nitrogen dioxide and ozonized air gives a high proportion of o-nitro derivatives in good yields (eq 3).19 Polynitration of arenes or nitration of strongly deactivated compounds requires the use of catalysts such as Boron Trifluoride Etherate or Methanesulfonic Acid.18

Nitration of Unsaturated Compounds.

Alkenes react with liquid nitrogen dioxide to give a complex mixture of compounds that include mainly 1,2-dinitroalkanes and 1-nitro-2-nitrosooxyalkanes.3,5,9 However, tetrasubstituted or halogenated alkenes usually give good yields of dinitro compounds (eq 4).

Addition of nitrogen dioxide to 1,1-dialkyl substituted alkenes affords good yields of nitroso nitrates.3,9 The same reaction in the presence of halogens leads to 1-nitro-2-haloalkanes which may undergo dehydrohalogenation to nitroalkenes.3,20 Alkynes react with nitrogen dioxide to give moderate yields of 1,2-dinitroalkenes.3,10

Oxidation.

Oxidation of alcohols and ethers with nitrogen dioxide gives aldehydes or ketones (eq 5).9,10,21 Nitrogen dioxide oxidizes primary amines to nitroalkanes, trialkylphosphines to phosphine oxides, and dialkyl sulfides to sulfoxides (without further oxidation to sulfones).9-11,22 Sulfides react with nitrogen dioxide to afford good yields of sulfonic acid anhydrides.9

Ponzio Reaction.

A general method for direct preparation of dinitromethylarenes is the oxidation of oximes with nitrogen dioxide (eq 6).3,5,6,10,11

Halogenation.

Nitrogen dioxide has been used in combination with halogens and metal halogenides for the halogenation of unreactive aromatic compounds and adamantane (eq 7).7,8,23

Related Reagents.

Iodine-Nitrogen Tetroxide.


1. Weaver, W. M. In The Chemistry of the Nitro and Nitroso Groups; Feuer, H., Ed.; Interscience: New York, 1970; Part 2, p 33.
2. Suzuki, H.; Murashima, T.; Shimizu, K.; Tsukamoto, K. CC 1991, 1049.
3. Padeken, H. G.; von Schickh, O.; Segnitz, A. MOC 1971, X/1, 76.
4. Larson, H. O. In The Chemistry of the Nitro and Nitroso Groups; Feuer, H., Ed.; Interscience: New York, 1970; Part 1, p 302.
5. Baumeyer, G. In Methodicum Chimicum; Zymalkowski, F., Ed.; Academic: New York, 1975; Vol 6, p 1.
6. Suzuki, H.; Takaoka, H.; Yamamoto, H.; Ogawa, T. BCJ 1988, 61, 2927.
7. Fieser, M.; Fieser, L. F. FF 1979, 7, 252.
8. Neidlein, R.; Leidholdt, R. CB 1986, 119, 844.
9. Ogata, Y. In Oxidation in Organic Chemistry; Trahanovsky, W. S., Ed.; Academic: New York, 1978; Part C, p 295.
10. Fieser, L. F.; Fieser, M. FF 1967, 1, 324.
11. Addison, C. C. CRV 1980, 80, 21.
12. Handbook of Preparative Inorganic Chemistry; Brauer, G., Ed.; Academic: New York, 1963; Vol. 1, p 488; Hackspill, L.; Benson, D. BSF 1949, 16, 479.
13. Benhaoua, H.; Piet, J. C.; Danion-Bougot, R.; Toupet, L.; Carrie, R. BSF 1987, 325; Radziejewski, C.; Ghosh, S.; Kaiser, E. T. H 1987, 26, 1227; Swindell, C. S.; Duffy, R. H. H 1986, 24, 3373.
14. Hartshorn, M. P.; Judd, M. C.; Vannoort, R. W.; Wright, G. J. AJC 1989, 42, 689.
15. Gong, L.; Dolphin, D. CJC 1985, 63, 401.
16. Pervez, H.; Onyiriuka, S. O.; Rees, L.; Rooney, J. R.; Suckling, C. J. T 1988, 44, 4555.
17. Squadrito, G. L.; Fronczek, F. R.; Watkins, S. F.; Church, D. F.; Pryor, W. A. JOC 1990, 55, 4322.
18. Suzuki, H.; Murashima, T.; Shimizu, K.; Tsukamoto, K. CC 1991, 1049; CI(L) 1991, 547.
19. Suzuki, H.; Ishibashi, T.; Murashima, T.; Tsukamoto, K. TL 1991, 32, 6591.
20. Rall, K. B.; Vil'davskaya, A. I. JOU 1974, 10, 1136.
21. Field, B. O.; Grundy, J. JCS 1955, 1110; Nishiguchi, T.; Okamoto, H. CC 1990, 1607; Nyarady, S. A.; Sievers, R. A. JACS 1985, 107, 3726.
22. Anello, L. G.; Van Der Puy, M. JOC 1982, 47, 377; Barton, D. H. R.; Narang, S. C. JCS(P1) 1977, 1114.
23. Cheprakov, A. V.; Makhon'kov, D. I.; Beletskaya, I. P. BAU 1987, 637; Cheprakov, A. V.; Makhon'kov, D. I.; Rodkin; M. A.; Beletskaya, I. P. JOU 1988, 24, 217.

Vladimir V. Popik

St. Petersburg State University, Russia



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