Methyl nitrate

Methyl nitrate is the methyl ester of nitric acid and has the chemical formula CH3NO3. It is a colourless volatile liquid that is explosive.

Not to be confused with nitromethane or methyl nitrite.
Methyl nitrate
Names
IUPAC name
Methyl nitrate
Other names
nitric acid, methyl ester, nitrooxymethane
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.009.039
UNII
Properties
CH3NO3
Molar mass 77.04 g/mol
Appearance Liquid
Density 1.203 g/cm3, liquid
Melting point −82.3 °C (−116.1 °F; 190.8 K)[1]
Boiling point 64.6 °C (148.3 °F; 337.8 K) (explodes)[1]
Explosive data
Detonation velocity 7900 m s−1 [2]
Hazards
Main hazards Toxic, High Explosive
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Synthesis

It can be produced by the condensation of nitric acid and methanol:[3]

CH3OH + HNO3 → CH3NO3 + H2O

A newer method uses methyl iodide and silver nitrate:[4]

CH3I + AgNO3 → CH3NO3 + AgI

Methyl nitrate can be produced on a laboratory or industrial scale either through the distillation of a mixture of methanol and nitric acid, or by the nitration of methanol by a mixture of sulfuric and nitric acids. The first procedure is not preferred due to the great explosion danger presented by the methyl nitrate vapour. The second procedure is essentially identical to that of making nitroglycerin. However, the process is usually run at a slightly higher temperature and the mixture is stirred mechanically on an industrial scale instead of with compressed air.

Explosive properties

Methyl nitrate is a sensitive explosive. When ignited it burns extremely fiercely with a gray-blue flame. Methyl nitrate is a very strong explosive, like nitroglycerin, ethylene glycol dinitrate, and other nitrate esters. The sensitivity of methyl nitrate to initiation by detonation is among the greatest known, with even a number one blasting cap, the lowest power available, producing a near full detonation of the explosive.

Despite the superior explosive properties of methyl nitrate, it has not received application as an explosive due mostly to its high volatility, which prevents it from being stored or handled safely.

Safety

As well as being an explosive, methyl nitrate is toxic and causes headaches when inhaled.

History

Methyl nitrate has not received much attention as an explosive, but as a mixture containing 25% methanol it was used as rocket fuel and volumetric explosive under the name Myrol in the Germany in World War II (during the Third Reich). This mixture would evaporate at a constant rate and so its composition would not change over time. It presents a slight explosive danger (it is somewhat difficult to detonate) and does not detonate easily via shock.[5][6]

According to A. Stettbacher, the substance was used as a combustible during the Reichstag fire in 1933.[7] Gartz shows in a recent work that only methyl nitrate with its production and explosion potential can represent the famous and mysterious "shooting water" from the German Feuerwerkbuch (fireworks book) of about 1420[8] (the oldest technical text in German language, handwritten in Dresden and later printed in Augsburg).[9]

The text in the fireworks book of 1420 is in extracts as follows (ancient German):

"Wildu mit wasser schyessen // daß du kein pulfer prauch // est vnd sterker und waiter // mit schewst dann als du daß aller // pest pulfer hast das yemann gehab //

en mag und ye gemacht wurd so ny // salpeter und distillier den mit wasser // vnd nym oleo benedicto dazu auch … // … vnd zunt sie an mit sinnen das du davon kommen magst … //

…mit disem wasser schewst du dreytousent schrit weit … // … es ist gar köstlich…"

Translated:

Do you want to shoot with water // so that you don't need powder // and stronger and further // you shoot than the very // best powder somebody might have had ever // and was made ever //

so take salpetre and distill it with water // and also take oleo benedicto (the oil of Benedicus) // and ignit it with the intention that you may get off

... with this water you will shoot threethousand foot // it is so delicious

Structure

The structure of methyl nitrate has been studied experimentally in the gas phase (combined gas-electron diffraction and microwave spectroscopy, GED/MW) and in the crystalline state (X-ray diffraction, XRD) (see Table 1).[4]

Gas phase structure of methyl nitrate determined by gas electron diffraction
Solid-state structure of methyl nitrate determined by X-ray diffraction

In the solid state there are weak interactions between the O and N atoms of different molecules (see figure).

Table 1: Structural parameters of methyl nitrate Bond lengths in Å , angles in °
Parameter
XRD GED/MW
C–O 1.451(1) 1.425(3)
N–OC 1.388(1) 1.403(2)
N–Oterminal 1.204(1) 1.205(1)
C–O–N 113.3(1) 113.6(3)
Oterminal-N-Oterminal 128.6(1) 131.4(4)

References
  1. CRC Handbook of Chemistry and Physics (64th ed.). 1983. pp. C–376.
  2. Meyer, R.; Köhler, J.; Homberg, A. (2007). Explosives (pdf) (6th ed.). Wiley-VCH. p. 212. ISBN 978-3-527-31656-4.
  3. Black, A. P.; Babers, F. H. (1939). "Methyl nitrate". Organic Syntheses. 19: 64.; Collective Volume, 2, p. 412
  4. Reichel, Marco; Krumm, Burkhard; Vishnevskiy, Yury V.; Blomeyer, Sebastian; Schwabedissen, Jan; Stammler, Hans‐Georg; Karaghiosoff, Konstantin; Mitzel, Norbert W. (2019-12-16). "Solid‐State and Gas‐Phase Structures and Energetic Properties of the Dangerous Methyl and Fluoromethyl Nitrates". Angewandte Chemie International Edition. 58 (51): 18557–18561. doi:10.1002/anie.201911300. ISSN 1433-7851.
  5. Meyer, Rudolf (2008). Explosivstoffe. Köhler, Josef., Homburg, Axel. (10., vollst. überarb. Aufl ed.). Weinheim: Wiley-VCH. ISBN 978-3-527-32009-7. OCLC 244068971.
  6. Koch, Ernst-Christian. Sprengstoffe, Treibmittel, Pyrotechnika. Walter de Gruyter GmbH & Co. KG (2. Auflage ed.). Berlin. ISBN 978-3-11-055784-8. OCLC 1107346317.
  7. Stettbacher, A. (1948). Spreng- und Schießstoffe. Rascher Verlag, Zürich.
  8. Gartz, Jochen (2007). Vom griechischen Feuer zum Dynamit : eine Kulturgeschichte der Explosivstoffe. Hamburg: E.S. Mittler & Sohn. ISBN 978-3-8132-0867-2. OCLC 153884719.
  9. "www.feuerwerkbuch.de". www.feuerwerkbuch.de. Retrieved 2020-06-15.
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