S-Trinitroanisole

Structures for these salts were first proposed by Meisenheimer (36) who found that he could obtain the same red salt by treating either s-trinitroanisole with potassium ethoxide or s-trinitrophenetole with potassium methoxide and assigned to it structure III. The product,... 

Spectroscopic evidence confirms the fact that the two Meisen-heimer compounds (36), that formed from s-trinitroanisole and eth-oxide ion and that formed from s-trinitrophenetole and methoxide ion, are identical. The two products give identical infrared t45) and visible spectra (46). The infrared spectrum is characterized by a shift in the N-0 symmetrical stretching frequency from 1343 cm. in s-trinitroanisole to 1291 cm. in the product and a shift in the N-0 asymmetrical stretching frequency from 1552 to 1492 cm. b These differences can be attributed to increased negative chai on the nitro groups and are consistent with the proixtsed structure 111. 

When s-trinitroanisole is added to excess sodium ethoxide in ethanol, two color-producing reactions occur (50). The first is a very rapid, reversible reaction, measurable at —60° to —80°, whose prod uct is probably a charge-transfer complex. This is accompanied by a slower reaction which occurs either concurrently or consecutively. Its forward rate can be measured at temperatures from —20° to - -10°, but its equilibrium lies too far to the right to permit determination of the reverse rate. The product of this reaction is the anion III, since a proton abstraction is improbable in this system and since the absorption spectrum of the product at room temperature is... 

These studies by Caldin et al. thus explain, in a completely satisfactory manner, Foster s originally puzzling observation that the interactions of alkoxides with s-trinitrotoluene, s-trinitroanisole, and s-trinitrobenzene result in products having strikingly different visible absorption spectra. In the first case, XII is formed by abstraction of a proton from the methyl group in the second, the process is one of addition to give III in the third, a charge-transfer complex is formed. These are three distinctly different structural types, and it is to be expected that their visible spectra will differ. 

Tire present paper describes a simple and convenient procedure for the identification of explosives viz Picramide Hexyl 2,4-Dinitrophenetole (DNP) Tetryl s-TNT s-TNB 2,4,6-Trinitroanisole (TNA) 2,4-Dinitroanisole (DNA) 2,4,6-Trinitro-phenetole (TNP) DNCB m-DNB and Picryl Chloride (PC) in ordnance stores as charge-transfer complexes with amines utilizing TLC... 

Giua, AttiAccadLincei 27 I, 379-82 247-52 (1918) CA 13, 1450, 1586 (1919) GazzChem-Ital 49 II, 146-54 (1919) CA 14, 1530 (1920) (Reactions betwn Phenylhydrazine and some aromatic nitrocompds contg a labde N02 group, such as TNT s, Trinitrobenzoic Acid, Trinitroxylene, Trinitrocresol Trinitroanisole were studied. In most cases the formation of nitrohydrazo compds was observed). 3) R.C. Elderfield, Explosives from Hydroxy and Amino... 

Gitis and Glaz [42] also confirmed Meisenheimer s view. They found that the ultra-violet spectrum of the addition product resulting from the reaction of potassium ethoxylate with trinitroanisole was identical with that of the addition product of potassium methoxylate and trinitrophenetole. Both products showed an absorption maximum at 485 mp. 

The kinetics and mechanism of Meisenheimer s reaction has been studied by Caldin and Ainscough [43] who utilized the reactions of addition of sodium etho-xylate to trinitroanisole, trinitrobenzene and trinitrotoluene. By using temperatures in the range from -70°C to -100°C they were able to reduce the reaction rate to a measurable value. On treating the addition product with acetic acid at temperatures ranging from -50°C to -80°C they obtained the starting product. Thus, the reaction was proved to be reversible, as for example in the case of trinitroanisole (TNA) ... 

According to Meisenheimer, this formula was confirmed by the fact that the product of the addition of potassium ethoxide to trinitroanisole is identical to the product of the addition of potassium methoxide to trinitrophenetole. Meisen-heimer s view was later confirmed by a number of workers, as for example Busch and Kogel [41], Bolian [42] and others (p. 203). 

The compound was first obtained by treating picryl chloride (Pisani [12]) or trinitroanisole with ammonia (Salkowski [13]). Later Witt and Witte [14] obtained it by the nitration of o- or p- nitroacetanilide in oleum solution. For the nitration a solution of KN03 in concentrated sulphuric acid was used. Spencer and Wright [15] applied Kym s method [lo] for the preparation of picramide, heating picric acid with urea at 173°C for 36 hr. The yield obtained was about 90% of the theoretical. 

When 2,4,6-trinitroanisole is treated witn methoxide in methanol, a red anion having the composition (CbH808N3) is produced. Such anions are called Meisenheimer complexes after the chemist who first suggested the correct structure. What structure do you think he suggested One of Meisenheimer s experiments compared the product of reaction of 2,4,6-trinitroanisole with ethoxide ion with the product of 2,4,6-trinitrophenyl ethyl ether with methoxide ion. What do you think he found ... 

There are several pieces of experimental evidence for the formation of a discrete intermediate in aromatic systems. One of the earliest was Meisenheimer s observation [19] that addition of potassium methoxide to 2,4,6-trinitrophenetole or addition of potassium ethoxide to 2,4,6-trinitroanisole produced identical compounds, (5), which on acidification produced in each case a mixture of methyl and ethyl picrates. Meisenheimer complexes, which are anionic a-adducts, are considered later in this chapter. 

The exclusive formation of the C-1 adduct between 2,4,6-trinitroanisole and n-butylamine has actually been detected, as a transient intermediate en route to AT-(n-butyl)picramide, by a low-temperature flow n.m.r. experiment. Further kinetic data for the reversible reaction between the 1,3,5-tri-nitrobenzene-methoxide cr-complex and aniline in DMSO-MeOH solutions, yielding the 1,3,5-trinitrobenzene-anilide dissociative mechanism involving rate-determining interconversion of free TNB and the protonated anilide complex. The failure of aromatic primary amines by themselves to form stable (7-complexes with TNB is due to an unfavourable overall equilibrium represented by equation (3), while the additional presence of the strong base... 

When picryl chloride is mixed with a solution of sodium methoxide in methanol, a red salt is formed (34). Analyses are consistent with a structure in which chloride has been replaced by methoxide and a molecule of sodium methoxide has been added. An alternate possibility would involve abstraction of a proton from initially formed trinitroanisole to give a salt which retains a molecule of methanol of crystallization. This product may be heated to 130° without loss of weight but is transformed by ethanol into a new salt in which a methyl has been replaced by an ethyl group. The possibility of a proton abstraction from the ring was considered improbable since deBruyn had shown that s-trinitrobenzene in xylene is not acted on by metallic sodium even at the boiling point of the solvent (35). 

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