Reaction nitrations

The most crucial observation concerning the effects of added species is that nitrate ion anticatalyses nitration without changing the kinetic form of the reaction. This shows that nitrate does not exert its effect by consuming a proportion of the nitronium ion, for, as outlined above, this would tend to bring about a kinetically first-order reaction. Nitrate ions must be affecting the concentration of a precursor of the nitronium... 

Other typical electrophilic aromatic substitution reactions—nitration (second entry) sul fonation (fourth entry) and Friedel-Crafts alkylation and acylation (fifth and sixth entnes)—take place readily and are synthetically useful Phenols also undergo elec trophilic substitution reactions that are limited to only the most active aromatic com pounds these include mtrosation (third entry) and coupling with diazomum salts (sev enth entry)... 

Particles are the major cause of the ha2e and the brown color that is often associated with smog. The three most important types of particles produced in smog are composed of organics, sulfates, and nitrates. Organic particles are formed when large VOC molecules, especially aromatics and cycHc alkenes, react with each other and form condensable products. Sulfate particles are formed by a series of reactions initiated by the attack of OH on SO2 in the gas phase or by Hquid-phase reactions. Nitrate particles are formed by... 

Isoxazoles are known at present to undergo the following electrophilic substitution reactions nitration, sulfonation, halogenation, chloroalkylation, hydroxymethylation, and mercuration. Repeated attempts to effect the Friedel-Crafts reaction in the isoxazole series in the authors laboratory failed. The isoxazole nucleus seems not active enough to react with weak electrophilic reagents. 

The central C-C double bond of dibenz[, /]oxepin displays the properties of an activated aromatic system and undergoes substitution reactions. Nitration and acid-catalyzed dcutcration gives the dibenzo[i>,/]oxepins 1 with the respective substituent in position 10.161... 

Many reactions, nitration, nitrosation, oxidation, etc are then possible. Titov s generalized scheme is... 

Liquid-liquid reactions (nitrations, oxidations or hydroxylations using H2O2, brominations, iodinations) 1-5 50-250 250 500... 

These trends have been quantified for some reactions. Nitration studies showed carbazole to react 222,000 times faster than benzene, with nitric acid-acetic anhydride having partial rate factors of 32,100 (C-1), 1,100 (C-2), 77,600 (C-3), and too small to measure (C-4). Carbazole reacts about 20 times more slowly than diphenylamine. The partial rate factor for nitration at C-3 can be compared with a value of 50,100 found for the perchloric add protodesilylation of 3-trimethylsilylcarbazole. ... 

Reactions. -Hydroxybenzoic acid undergoes the typical reactions of the carboxyl and hydroxyl moieties. When heated above its melting point, it decomposes almost completely into phenol and carbon dioxide. It reacts with electrophilic reagents in the predicted manner and does not undergo the Friedel-Crafts reaction. Nitration, halogenation, and sulfonation afford the 3-substituted products. Heating -hydroxybenzoic acid with 8 IV-nitric acid results in a 95% yield of picric acid. In a similar fashion, treatment with chlorine water yields 2,4,6-trichlorophenol (50). 

A review of experimental work prompted the suggestion of the importance of dipolar interactions (Hammond and Hawthorne, 1956). de la Mare and Kidd (1959), observing a parallelism in the parajmeta and ortho/meta ratios, predicted the ortho effect to be primarily electronic in origin. Norman and Radda (1961) explored the general significance of this idea. They studied the orthojpara ratios for the substitution of a series of monosubstituted benzenes by two reagents with the same electrophilic properties but different steric requirements. The reactions, nitration by N02+ and chlorination by CI+, fulfill the requirements. The results are summarized in Table 3. 

The importance of the steric effect accounts for the spread of the data for lf-N in the substitution reactions. Nitration and non-catalytic chlorination, reactions of modest steric requirements, define points which fall above the arbitrary reference line. Bromination, a reaction of somewhat greater steric requirements, is not accelerated to the extent anticipated on the basis of the results for nitration or chlorination. The benzoylation reaction with large steric requirements is two orders of magnitude slower than the equally selective chlorination reaction. The unusually small ratio for lf-N/2f-N for the acylation reaction is a further indication of the steric effects. Apparently, the direct substitution reactions of naphthalene respond to the retarding steric influence of the peri hydrogen in much the same way as for other ortho substituents. 

Compound 33 was needed to make some antimalarial drugs.12 We prefer not to disconnect the OEt group (Guideline 3) and there are good reactions-nitration and chloromethylation-that would go in the right position (ortho or para) to the activating OEt group. Either disconnection a or b could be tried first. 

All explosive materials contain oxygen, which is needed for the explosive reaction to take place. The oxygen can be introduced by chemical reactions (nitration) or by mechanical incorporation of materials containing bound oxygen. The most important solid-state oxidizers are nitrates, especially -> Ammonium Nitrate and -> Sodium Nitrate for explosives -> Potassium Nitrate for -> Black Powder and ion exchanged -> Permitted Explosives, potassium chlorate for -> Chlorate Explosives and for pyrotechnical compositions Ammonium Perchlorate (APC) for -> Composite Propellants. 

The ring system (1) did not undergo any other electrophilic substitution reactions (nitration, sulfonation, Friedel-Crafts, Vilsmeier formylation), was inert to sodamide, could not be metalated with butyllithium and could not be readily oxidized with hydrogen peroxide to an AC-oxide (66JOC265). Compound (1) could not be reduced at atmospheric pressure by hydrogen but at 3 atm using a palladium-charcoal catalyst the 5,6,7,8-tetrahydro derivative (90) was obtained (75G1291). 

All explosive materials contain oxygen, which is needed for the explosive reaction to take place. The oxygen can be introduced by chemical reactions (nitration) or by mechanical incorporation of mate-... 

A better method for the same reaction (nitration of benzenes) is to use the product of nitration of pyrazole2 13. When the nitration is carried out in the absence of strong acid, the product is the A-nitro compound 14, a stable neutral molecule because a proton can be lost from the other nitrogen atom. This compound is stable but reacts with the Lewis acid BF3 to give an intermediate 15 that nitrates benzene efficiently. It is probable that the C-ni (ration of pyrazoles also takes place via such an intermediate as 15, see below. 

Keywords gas-solid reaction, nitration, hydantoin, N-nitrohydantoin, nitramine, nitrogen dioxide, nitrogen monoxide... 

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