Acetyl nitrate nitration with

Fig. 5.1. Zeroth-order rates of nitration with acetyl nitrate compared with those for other systems, (a) HNOa/ sulpholan, (i) HNO3/CCI4, (c) AcONOj/AcjO/O % AcOH, (d) AcONOj/AcaO/O % AcOH/[mesitylene] = o-8 mol l-i,n (e) AcONOj/AcaO/ [AcOH] = 2-2moll-i,ii >(/)AcONOa/AcaO/[AcOH] = 1-96 mol l-i and (g) AcONOa/ AcaO/[AcOH] 3 9i mol l-i/[mesitylene] = o-8 mol 1-i H.

The observation of nitration at a rate independent of the concentration and the nature of the aromatic means only that the effective nitrating species is formed slowly in a step which does not involve the aromatic. The fact that the rates of zeroth-order nitration under comparable conditions in solutions of nitric acid in acetic acid, sulpholan and nitromethane differed by at most a factor of 50 indicated that the slow step in these three cases was the same, and that the solvents had no chemical involvement in this step. The dissimilarity in the rate between these three cases and nitration with acetyl nitrate in acetic anhydride argues against a common mechanism, and indeed it is not required from evidence about zeroth-order rates alone that in the latter solutions the slow step should involve the formation of the nitronium ion. 

Such arguments are based on the assumption that the nitronium ion is the nitrating agent in all of the media under consideration as regards nitration with acetyl nitrate, they certainly do not prove the efficacy of the nitronium ion unless the participation of the latter can be shown to be also consistent with the kinetic evidence. 

The mechanisms of nitration with acetyl nitrate in acetic anhydride... 

The fact that nitration with acetyl nitrate is sometimes accompanied by acetoxylation has been mentioned ( 5.3.3). In proposing the ion pair ACONO2H+ NOg- as the nitrating agent, Fischer, Read and Vaughan also suggested that it was responsible for the acetoxylation, which was regarded as an electrophilic substitution. 

The results are only slightly dependent upon conditions for nitrations with acetyl nitrate see ref. 59, and in sulphuric acid ref. 46. 

Furan and acetyl nitrate give an addition product which is converted by pyridine into 2-nitrofuran (Scheme 10). The positions in which substituted furans undergo nitration with acetyl nitrate are shown in diagrams (59)-(63) and illustrate the rules of orientation. 

Trifluorofuran is resistant to simple nitration with acetyl nitrate instead, the nitro and acetoxy groups are incorporated in the structure by 2,5-addition to yield a mixture of the cis-and /raw-isomers (Table 10).184... 

The results are only slightly dependent upon conditions for nitrations with acetyl nitrate see ref. 59, and in sulphuric acid ref. 46. t The rate constants given refer to the acidities quoted, but the accompanying isomer proportions usually refer to slightly different acidities. However, as noted, isomer proportions are not much affected by changes in acidity. Rate profiles are available for all of the compounds.48... 

Pyrrole and its simple alkyl derivatives are polymerized by many of the typical acidic electrophiles. Nitration with acetyl nitrate (Scheme 4.31) under mild conditions gives the 2-nitro compound, together with small amounts of 3-nitropyrrole. Halogenation is rapid but it gives a complex mixture of polyhalogeno compounds. 

Very often nitration with nitric acid-acetic anhydride solution is referred to as nitration with acetyl nitrate (Vol. I, p. 44). Petrov and co-workers [24] experi-... 

The nitration of enol acetates with acetyl nitrate is a regiospecific electrophilic addition to the 3-carbon of the enol acetate, followed by a hydrolytic conversion of the intermediate to the a-nitro ketone. With enol acetates of substituted cyclohexanones the stereochemistry is kinetically established. So, 1-acetoxy-4-methylcyclohexene (22) yields the thermodynamically less stable rrans-4-methyl-2-nitrocylo-hexanone (24) in greater proportion cis. trans = 40 60) (equation 8). This mixture can be equilibrated in favor of the thermodynamically more stable cis diastereomer (23) (cis. trans = 85 15). Nitration of 1-ace-toxy-3-methylcyclohexene (25) leads to frans-3-methyl-2-nitrocyclohexanone (26), which is also the thermodynamically more stable isomer (equation 9). No stereoselection occurs in the kinetically controlled nitration with acetyl nitrate of l-acetoxy-5-methylcyclohexene (27 equation 10), but the 1 1 mixture of the 5-methyl-2-nitrocyclohexanones can be equilibrated in favor of the trcms diastereomer (28) (cis trans = 10 90). 2-Alkyl-2-nitrocyclohexanones cannot be prepared in acceptable yields by nitration of the corresponding enol acetates with acetyl nitrate. 

Nitrodesilyiation is usually faster than nitrodeprotonation because the nitrosilylbenzenium ion is stabilized by the silyl substituent. Deans and Eabom showed that l,4-bis(trimetbykilyl) benzene undergoes nilrodesily-lation on nitration with acetyl nitrate [143]. Acetyl nitrate is the reagent of choice, because nitration with a nitric add/sulfuric acid system will lead primarily to protodesilylation. 

Nitric acidlacetic anhydride Nitrations with acetyl nitrate 2-Acetoxynitro compounds and 3-nitroalkenes from alkenes... 

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