In nitration reactions

Fluorinated Acids. This class of compounds is characterized by the strength of the fluorocarbon acids, eg, CF COOH, approaching that of mineral acids. This property results from the strong inductive effect of fluorine and is markedly less when the fluorocarbon group is moved away from the carbonyl group. Generally, their reactions are similar to organic acids and they find apphcations, particularly trifluoroacetic acid [76-05-1] and its anhydride [407-25-0] as promotors in the preparation of esters and ketones and in nitration reactions. 

The nitronium ion, N02+, derived from N02, is the attacking species in nitration reactions (see Chapter 9). Also, liquid N204 has been rather extensively studied as a nonaqueous solvent, and autoionization, to the extent it occurs, appears to be as follows ... 

Nitric acid is used for nitration of many organic compounds. Many nitro derivatives are made by such reactions. Pure nitric acid or often its combination with concentrated sulfuric acid is employed in these syntheses. When pure nitric acid is dissolved in concentrated sulfuric acid, it forms nitronium ion, N02, the active species in nitration reactions ... 

Fume-Off. The oxidative destruction of byproducts in nitration reactions Ref Coll, "Summary Report of Div 8 NDRC", Vol 1(1946), p 153... 

Acetone decomposes violently when brought in contact with H2S04/HN03 mixtures such as are used in nitration reactions. This is especially... 

Since the nitro group is usually introduced by electrophilic aromatic substitution (Chapter 22) and halides direct ortho/para in nitration reactions, a common sequence is nitration followed by nucleophilic substitution. 

After our success in nitrating moderately active monosubstituted benzenes with acetic anhydride and nitric acid over zeolite p,11 we decided to try the use of trifluoroacetic anhydride and nitric acid over zeolite p for nitration of deactivated substrates. Although trifluoroacetyl nitrate is known to be more active than acetyl nitrate, it has not been widely used in nitration reactions.15 Nitrobenzene has been successfully nitrated using fuming nitric acid and trifluoroacetic anhydride in equimolar proportions at 45-55 °C.16 However, no dinitration of toluene was reported. 

The N02+ ion is the attacking species involved in nitration reactions, so H2S04 increases the concentration of a positive attacking species and is, therefore, functioning as an acid catalyst (see Chapter 5). 

This ion (NO ) is directly involved, not only in the dissociation of HN03 itself, but also in nitration reactions and in solutions of nitrogen oxides in HN03 and other strong acids. 

It appears that in nitration reactions the nitronium ion is sufficiently powerful as an electrophile to enable ring-substitution of the aryl azide to compete adequately with the decomposition pathway, and modest yields of nitroaryl azides may be achieved It is significant that... 

Aramides have a 40°C higher melting point with durene diamine than with p-phenylene diamine(5). Furthermore, durene diamine may be able to be produced at a price equivalent to or lower than that of p-phenylene diamine. This arises because the linear substitution is not generally simple in nitration reactions for durene, however, there is no other option. 

Acylation reactions with acid chlorides86 also lead to N-substituted products. N-Acyl- and N-sulfonylimines react analogously in nitration reactions (see Section II,A,4). 

A few typical examples of electrophilic and oxidative reactions are summarized in Scheme 8.5.6 bromination usually gives substitution rather than addition products, whereas in nitration reactions one also observes electrophilic substitution and the ribose must be protected. Hydroxy methylation with formaldehyde occurs preferrably at C5 of uridine. 

In particular, di- and polyalkyl benzenes having alkyl groups ortho or para to each other, so that mutual activation toward electrophilic attack can occur, may undergo from 25% to as much as 80% ipso attack in nitration reactions. (1,1) As pointed out by Professor Myhre, the ipso nitroarenium ions thus formed can undergo a variety of further processes depending on the nature of the substrate and reaction conditions. (4) One of these reactions is shown below. 

The specification of diethylene glycol for nitration reaction is Usted in Table 5.18. The composition of the mixed acid in nitration reaction of diethylene glycol ... 

The question of other species acting as electrophiles in nitration reactions arises principally in the case of nitration using solutions prepared by dissolving nitric acid in acetic anhydride. Acetyl nitrate is formed in such solutions, and so the question arises as to whether it is the nitrating species. Such solutions are very potent nitrating... 

For example, the nitration of benzene and other aromatic compounds is often strongly limited by the mass transfer performance within the reactor that is used. In particular in the case of biphasic nitration reactions, a good mass transfer performance is essential to suppress the formation of unwanted by-products such as higher nitrated compounds (e.g. dinitro and trinitro compounds) or oxidation products. Therefore, the use of microreactors offers a good possibility to overcome common restrictions in mass transport and thus achieve higher yields and selectivities in nitration reactions. 

---