Benzoyl Nitrate1

[6786-32-9]  · C7H5NO4  · Benzoyl Nitrate  · (MW 167.12)

(nitrating agent for arenes and some other functionalities; benzoylation may also occur; oxidizes thiols to disulfides, thioethers to sulfoxides, and HCl to chlorine)

Physical Data: not known; presumably liquid at room temperature. d 1.3 g cm-3 at 0 °C.2

Solubility: miscible with common organic solvents.

Form Supplied in: not commercially available.

Preparative Methods: a standard approach is to add an equivalent amount of PhCOCl to a solution of freshly dried AgNO3 in MeCN at -20 °C, and to filter off AgCl. The solution may be kept at -40 °C for some time, but develops a precipitate of benzoic acid.3 CCl4 may also be used as a solvent.4 Alternatively, PhCOCl in MeCN is added dropwise to a rapidly stirred solution of AgNO3 in MeCN plus the required substrate, such as PhR, to be nitrated; eventually this is done at reflux temperature.3 This is likely to work satisfactorily only if the target reaction is sufficiently rapid.

Purification: kinetic and product studies (such as in the nitration of toluene4 and also involving substituted analogs of the title reagent) yield an invariant isomer composition of the nitrotoluenes,3 suggesting that the active ingredient may be N2O5, present in equilibrium with benzoic anhydride.

Handling, Storage, and Precautions: unstable above room temperature; stock solution may be stored in the cold,3 but the use of freshly (or in situ) prepared reagents is recommended. This reagent should be handled in a fume hood.

Electrophilic Nitration (and Benzoylation).

Regular nitration of toluene typically gives a 50% yield of MeC6H4NO2, with o:m:p = 62:4:34.3 In the presence of Al-exchanged mordenite a 99% yield has been claimed, the isomer distribution now being 67:1:32;5 with H-ZSM 11, selectivity to para was even 98%. Further examples include PhR with R = Et, n-Pr, i-Pr, t-Bu; p-terphenyl gave a 71% crude yield of p-NO2C6H4C6H4C6H4NO2-p. With o-xylene, 3- and 4-nitro-o-xylene (28% yield, ratio 32:68) and the corresponding benzoyloxy derivatives (16%, ratio 5:95) are formed; the benzoates apparently arise via ipso attack of nitronium ion, p- or o-addition of benzoate ion, and elimination of HNO2.6 Thiophene gives 2- and 3-nitrothiophene, in a ratio of ca. 6.7 Secondary amines can be converted into the N-nitro derivative8 (eq 1). Primary arylamines (ArNH2), however, give ArNHOBz in high yield.8 Indoles with a free 3-position are converted into their 3-nitro derivatives; 3-methylindole leads to 3-methyl-2-nitroindole, but yields in these reactions are modest (<35%).9


Benzenethiol is quantitatively converted into PhSSPh.2 Thiol ethers rapidly give sulfoxides in high yield, without further oxidation to sulfones, even well below 0 °C.10

Other Applications.

The oxidative power of the reagent can be directed to effect chlorination. In MeCN with aq. HCl it liberates Cl2, and when performing the reaction in the presence of e.g. toluene, up to 1.7 mol of chlorotoluene (o:p = 54:46) per mol of benzoyl nitrate could be obtained.11 Alcohols (ROH) are converted into RONO2 and PhCOOH.2


Upon reflux in CCl4 (9 h) PhCl, PhCO2H, some PhNO2, and CO2 are produced.12 In refluxing benzene, biphenyl, benzoic anhydride, PhCO2H, and PhNO2 arise. In both cases radical reactions occur.13 Controlled gas-phase thermolysis at ca. 290 °C of RCO2NO2 can afford RNO2 in ca. 50% yields.14

1. (a) FF 1975, 5, 25. (b) Hoggett, J. G.; Moodie, R. B.; Penton, J. R.; Schofield, K., Nitration and Aromatic Reactivity; Cambridge Univ. Press: Cambridge, 1971; p 76.
2. Francis, F. CB 1906, 39, 3798.
3. Kurz, M. E.; Yang, L. T. A.; Zahora, E. P.; Adams, R. C. JOC 1973, 38, 2271.
4. Gold, V.; Hughes, E. D.; Ingold, C. K. JCS 1950, 2467.
5. Nagy, S. M. J. Mol. Catal. 1991, 64, L31.
6. Kurz, M. E.; Woodby, E. S. JOC 1976, 41, 2443.
7. &OOuml;stman, B. AK 1962, 19, 499.
8. Butler, T. H. CB 1906, 39, 3804.
9. Berti, G.; Da Settimo, A.; Nannipieri, E. JCS(C) 1968, 2145.
10. Louw, R.; Vermeeren, H. P. W.; van Asten, J. J. A.; Ultée, W. J. CC 1976, 496.
11. Kurz, M. E.; Zahora, E. P.; Layman, D. JOC 1973, 38, 2277.
12. Horacek, I.; Hrabak, F. CCC 1974, 39, 2608.
13. Barlow, L. R. T 1968, 24, 4913.
14. Bachman, G. B.; Biermann, T. F. U.S. Patent 3 689 576, 1972.

Robert Louw

Leiden University, The Netherlands

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