Explosophore

Explosophores are functional groups in organic chemistry that give organic compounds explosive properties.

History

The term was first coined by Russian chemist V. Pletz in 1935.^[1] and originally mistranslated in some articles as "plosophore". Also of note is an auxoexplose concept (similar to chromophore and auxochrome concept), which is a group that modifies the explosive capability of the molecule. The term explosophore has been used more frequently after its use in books such as Organic Chemistry of Explosives by J. Agrawal and R. Hodgson (2007)'.

Properties

Nitrogen-containing explosophores (groups I, II and II below) are particularly strong because in addition to providing oxygen they react to form molecular nitrogen, which is a very stable molecule, and thus the overall reaction is strongly exothermic. The gas formed also expands, causing the shock wave which is observed.

Classification

Pletz grouped the explosophores into eight distinct categories. ^[2][3] It has been suggested that the current list is insufficient and that several other new categories should be added.

I. −NO₂, −ON=O and −ONO₂

These represent

• the nitro group, in which a nitrogen atom bonds to an organic molecule,
• the nitrite group, in which oxygen is bonded to the organic molecule, and
• nitrate esters, in which a nitrogen atom is located between one oxygen bonded to the organic molecule and the other two oxygen atoms.

By far the most commercially used explosives are nitrate and nitrite based.

II. −N=N− and −N⁻=N⁺=N⁻−

The azo and azide groups respectively, connected to organic/inorganic compounds (e.g. AgN₃, Pb(N₃)₂, NH₄N₃)

III. −R_nNX_m

The halogenated nitrogen group X:halogen (for example NI₃ and RNCl₃)

IV. −C=N−O−

The fulminate group (example HONC and Hg(ONC)₂)

V. −OClO₂ and −OClO₃

The chlorate and perchlorate groups respectively, connected to organics/inorganics (e.g. KClO₃, FOClO₃)

VI. −O−O− and −O₃−

The peroxide and ozonide groups respectively, connected to organics/inorganics (e.g. acetone peroxide, butanone peroxide)

VII. −C≡C⁻ M⁺

The acetylide group with its metal derivatives

VIII. A metal atom connected by an unstable bond to the carbon of certain organic radicals

This class contains for instance organic compounds of mercury, thallium, and lead.

Other

Other substances have been characterised as explosophores outside of the eight classes as defined by Pletz.

A functional group that is frequently considered as an explosophore is picrate, the salts or ethers of picric acid (2,4,6-trinitrophenol), which gains its explosive capability from the nitrate groups attached to it.

References