Anisole nitration with

Without further studies little weight can be given to these ideas. In particular there is the possibility that with acetanilide, as with anisole, nitrosation is of some importance, and further with nitrations in sulphuric acid the effect of protonation of the substrate needs quantitative evaluation. The possibility that the latter factor may be important has been recognised, and it may account for the difference between nitration in sulphuric acid and nitration with nitronium tetrafluoroborate. 

In order to examine the effect of the nitrating agent, anisole can be also treated with Me02CPyN02, PyN02 and MeOPyN02. Control experiments carried out simultaneously in the dark establish the absence of any electrophilic (thermal) component to anisole nitrations under all charge-transfer conditions (Kim et al., 1993 ). The photochemical nitrations of... 

Isomeric product distributions. Isomeric product distributions obtained from toluene and anisole have been the subject of considerable mechanistic discussion in electrophilic aromatic nitration (Schofield, 1980 Olah et al., 1989). As applied to nitrations with iV-nitropyridinium ion, the yellow colour of the EDA complex immediately attendant upon the mixing of toluene and PyN02 in acetonitrile persists for about a day (in the dark), whereas the charge-transfer colour of toluene and Me2PyNOj is discharged within 10 min at 25°C. Both bleached solutions afford an identical product mixture (81), consisting of o- (62%), m- (4%) and p-nitrotoluenes (34%)... 

Careful nitration of anisole (CH3OC6H5) with a new nitrating reagent gives a mixture of 4-nitroanisole and 2-nitroanisole. The section of the NMR spectrum below is from the aromatic region of the crude reaction mixture which is a mixture of the 4- and 2-nitroanisoles. Determine the relative amounts of the two products in the reaction mixture from the integrals in the spectrum. 

A partial dearylation of diarylether during nitration had already been observed by Reilly, Drumm and Barrett [154], The dealkylation, observed by Schramm and Westheimer, has been confirmed by Ingold and his co-workers [152], For example p- chloroanisole, when nitrated with a 6N solution of nitric acid in the presence of acetic acid at 20°C gave 4-chloro-2-anisole in 66% yield and 4-chloro-2,6-dinitrophenol in 33% yield of theory. 

On the other hand Ingold and co-workers [144,155a] have proved that the presence of nitrous acid in the nitrating acid decreases the rate of nitration of aromatic compounds in general with the exception of phenols. The same holds true for phenyl ethers (e.g. anisole) which are more difficult to nitrate with higher concentrations of nitric acid in acetic acid (e.g. 8N) in the presence of nitrous acid, whereas with a less concentrated nitric acid (e.g. 5N), nitrous acid accelerates the reaction. 

The authors of this work were concerned chiefly with additions to alkenes, and evidence about the mechanism of aromatic nitration arises by analogy. Certain aspects of their work have been repeated to investigate whether the nitration of aromatic compounds shows the same phenomena ( 5-3-6). It was shown that solutions of acetyl nitrate in acetic anhydride were more powerful nitrating media for anisole and biphenyl than the corresponding solutions of nitric acid in which acetyl nitrate had not been formed furthermore, it appeared that the formation of acetyl nitrate was faster when 95-98% nitric acid was used than when 70 % nitric acid was used. 

Acetoxylation and nitration. It has already been mentioned that 0- and m-xylene are acetoxylated as well as nitrated by solutions of acetyl nitrate in acetic anhydride. This occurs with some other homologues of benzene, and with methyl phenethyl ether,ii but not with anisole, mesitylene or naphthalene. Results are given in table 5.4. 

Anisole] = 0 4 mol 1 zeroth-order reactions, except for that with added nitrate, which was of the first order with respect to the concentration of anisole. 

Other substituents which belong with this group have already been discussed. These include phenol, anisole and compounds related to it ( 5.3.4 the only kinetic data for anisole are for nitration at the encounter rate in sulphuric acid, and with acetyl nitrate in acetic anhydride see 2.5 and 5.3.3, respectively), and acetanilide ( 5.3.4). The cations PhSMe2+, PhSeMe2+, and PhaO+ have also been discussed ( 9.1.2). Amino groups are prevented from showing their character ( — 7 +717) in nitration because conditions enforce reaction through the protonated forms ( 9.1.2). 

The nitration of 6-methoxyquinoxaline in concentrated sulfuric acid at 0°C gives 6-methoxy-5-nitroquinoxaline. The position of the nitro group is confirmed by reduction of the product to 5-amino-6-methoxy-quinoxaline identical with a sample prepared from 2,3,4-triamino-anisole and glyoxal ... 

Dinitro Methyl Anisole (4-Nitro-2-nitromethyl anisole, 3-Nitro-6-methoxynitromethyI toluol. or Methyl-[5-nitro-2-nitromethylphenyl] -ether). CH3.0.(N02)C6H3.CH2N02, mw 212.18, N 13.21%, OB to C02 —113.11%, cryst, mp 93—94°. Prepd from 4-nitro-2(lodomethyl) anisole in ether-ben2ene soln by treatment for 3 days at RT with Ag nitrate. The sodium salt explodes violently on heating Refs 1) Beil, not found 2) G. Bendy,... 

The charge-transfer nitrations of the aromatic donors are generally carried out to rather low actinic conversions to avoid complications from light absorption by the nitroarene products, and in duplicate sets (with a dark control) to monitor simultaneously any competition from thermal processes. For example, the yellow solution of anisole and Me2PyN02 in acetonitrile at — 40°C is irradiated with the aid of the cut-off filter that effectively removes all excitation light with Aexc<400nm. After reasonable photochemical conversions are attained, the H NMR spectrum is found to be virtually identical to that of the reaction mixture obtained by electrophilic (thermal) nitration (60). 

The ambiphilic reactivity of aromatic cation radicals, as described in Schemes 12 and 13, is particularly subtle in the charge-transfer nitration of toluene and anisole, which afford uniformly high (>95%) yields of only isomeric nitrotoluenes and nitroanisoles, respectively, without the admixture of other types of aromatic byproducts. Accordingly, let us consider how the variations in the isomeric (ortho meta para) product distributions with... 

Since the latter conditions pertain to aromatic nitration solely via the homolytic annihilation of the cation radical in Scheme 16, it follows from the isomeric distributions in (81) that the electrophilic nitrations of the less reactive aromatic donors (toluene, mesitylene, anisole, etc.) also proceed via Scheme 19. If so, why do the electrophilic and charge-transfer pathways diverge when the less reactive aromatic donors are treated with other /V-nitropyridinium reagents, particularly those derived from the electron-rich MeOPy and MePy The conundrum is cleanly resolved in Fig. 17, which shows the rate of homolytic annihilation of aromatic cation radicals by NO, (k2) to be singularly insensitive to cation-radical stability, as evaluated by x. By contrast, the rate of nucleophilic annihilation of ArH+- by pyridine (k2) shows a distinctive downward trend decreasing monotonically from toluene cation radical to anthracene cation radical. Indeed, the... 

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