Picryl chloride synthesis

Halogen substituents withdraw electron density from the aromatic nucleus but direct olp-through resonance effects. The result is that halobenzenes undergo nitration with more difficulty relative to benzene. The nitration of chlorobenzene with strong mixed acid gives a mixture of 2,4- and 2,6-isomeric dinitrochlorobenzenes in which the former predominates." The nitration of 2,4-dinitrochlorobenzene to 2,4,6-trinitrochlorobenzene (picryl chloride) requires an excess of fuming nitric acid in oleum at elevated temperature. Both are useful for the synthesis of other polynitroarylene explosives but only 2,4-dinitrochlorobenzene finds industrial importance (Sections 4.8.1.2 and 4.8.1.3). 

The presence of three nitro groups on the aromatic ring of picryl chloride makes the chloro group extremely reactive towards nucleophiles. Picryl chloride (87) is hydrolyzed to picric acid (4) in the presence of hot water or aqueous sodium hydroxide. Aminolysis of picryl chloride in the presence of primary and secondary amines is complete in minutes at room temperature. Picryl chloride is therefore a very useful starting material for the synthesis of a range of other picryl derivatives. The reaction of picryl chloride (87) with ammonia can be used to synthesize 2,4,6-trinitroaniline (53) (picramide). Treatment of picryl chloride with alcohols under reflux forms picric acid and the alkyl chloride of the corresponding alcohol, whereas the same reaction in the presence of alkali metal hydroxides, or the alkoxide anion of... 

The conjugation in 2,2, 4,4, 6,6 -hexanitroazobenzene (HNAB) (90) is also reflected in its thermal stability (m.p. 220 °C). The synthesis of HNAB from picryl chloride and 2,4-dinitrochlorobenzene is discussed in Sections 4.8.1.2 and 4.8.1.3 respectively. 3,3, 5,5 -Tetraamino-2,2, 4,4, 6,6 -hexanitroazobenzene (149) has been synthesized by an unusual but efficient route which involves the nitration-oxidative coupling of 3,5-dichloroaniline (147) on treatment with nitric acid, followed by reaction of the resulting product, 3,3, 5,5 -tetrachloro-2,2, 4,4, 6,6 -hexanitroazobenzene (148), with ammonia. Both the tetrachloro (148) and tetraamino (149) derivatives exhibit high thermal stability. 

Similar routes have been used for the synthesis of other polynitrophenylenes. 1,3,5-Tris(2,4,6-trinitrophenyl)-2,4,6-trinitrobenzene (160) is synthesized from the reaction of 1,3,5-trichloro-2,4,6-trinitrobenzene with three equivalents of picryl chloride in the presence of activated copper powder in refluxing mesitylene. " 2,2",4,4, 4",6,6, 6"-Octanitro-m-terphenyl (161) has been synthesized from picryl chloride and l,3-dichloro-4,6-dinitrobenzene. ... 

Amino-1,2,4-triazole is a useful starting material for the synthesis of many 1,2,4-triazole-based explosives. Jackson and Coburn synthesized a number of picryl- and picrylamino-substituted 1,2,4-triazoles. PATO (99) is synthesized from the reaction of 3-amino-1,2,4-triazole (98) with picryl chloride (67). ° PATO has also been synthesized from the reaction of 3-amino-l,2,4-triazole with A,2,4,6-tetranitromethylaniline (tetryl). PATO has a low sensitivity to impact and is thermally stable up to 310 °C. PATO (VOD 7469 m/s) exhibits lower performance to TATB (VOD 8000 m/s) which is the common benchmark standard for thermal stability and insensitivity in explosives. 

Agrawal and co-workers reported the synthesis of two tetrazole-based explosives, namely, 5-picrylamino-l,2,3,4-tetrazole " (PAT) (149) and 5,5 -styphnylamino-l,2,3,4-tetrazole (SAT) (150) from the reaction of 5-amino-1,2,3,4-tetrazole (148) with picryl chloride and styphnyl chloride respectively. These explosives have been studied for their thermal and explosive properties. The thermal stability of SAT (exotherm peak at 123 °C) is lower than PAT (exotherm peak at 185 °C), which is possibly attributed to the decreased electron-withdrawing power of the picryl group by being attached to two tetrazole units. PAT and SAT have calculated VODs of 8126 m/s and 8602 m/s respectively. ... 

Methylnitramine decomposes explosively in contact with concentrated sulphuric acid. It is evolved when aniline reacts with tetryl, a diphenylamine derivative (p. 51) is produced simultaneously. Methylnitramine reacts with picryl chloride to form tetryl. The structure of tetryl (p. 40) was first proved by this synthesis. 

Methylnitramine is produced when aniline reacts with tetryl in benzene solution, and when ammonia water or barium hydroxide solution acts upon dinitrodimethyloxamide. The structure of tetryl was first proved by its synthesis from picryl chloride and the potassium salt of methylnitramine. 

Thiazolo[3,2-6]isoquinolines.—[CaNS-CsN-Ce]. In continuation of their investigation of cyclizations involving the loss of nitrous acid, Krbhnke et alf have described a synthesis of thiazolo[3,2-Z>]isoquinolines. 2-Methyl-3-phenacylbenzothiazolium bromide (315 R = Ph) is found to react with picryl chloride to form (316). In common with picryl-substituted ylides, this is cyclizable, involving its nitroaryl and A -methylene groups, to yield... 

Pagoria and co-workers synthesized a number of thermally stable explosives from the reaction of the sodium salt of ANTA with chloro-substituted arylenes and A-heterocycles. These include the synthesis of (117) from picryl ehloride, PRAN (118) from 2-chloro-3,5-dinitropyridine, IHNX (119) from 2,4-dichloro-5-nitropyrimidine, (120) from 1,5-dichloro-2,4-dinitrobenzene, and (121) from 4-chloro-6-(3-nitro-l,2,4-triazolyl)-5-nitropyrimidine. Coburn and co-workers " reported the synthesis of the tetrazine (122) and the triazine (123) from the reaction of the sodium salt of ANTA with 3,6-dichlorotetrazine and cyanuric chloride respectively. 

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