Nitration of 4-Methoxyazoxybenzenes.
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Abstract:
When 4-methoxy-NNO-azoxybenzene [1 a] was kept in 20% nitric acid (HNO3-AcOH-H2O)at 40°C, 4-methoxy-ONN-4'-nitroazoxybenzene (6β) was obtained as a nitration product but the isomerization of 1α to 4-methoxy-ONN-azoxybenzene [1β] did not take place at all. In this reaction, 4-methoxy-NNO-4'-nitroazoxybenzene [6α] formed by para-nitration of 1α seems to isomerize to 6β immediately. However, neither nitration nor isomerization took place in the reaction of 1β with 20% nitric acid (HNO3-AcOH-H2O) under the similar reaction conditions. It is co nvenient method to obtain pure 1β that is the nitration of a mixtare 1α and 1β with dilute nitric acid under the mild conditions.Keywords:
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G. M. Bennett, J. C. D. Brand and G. Williams, J. Chem. Soc., 1946, 869 DOI: 10.1039/JR9460000869
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This work has studied the effects on the nitration of toluene by 100% nitric(V) acid and a nitric(V) acid/dichloromethane mixture. The results show that the amount of meta-nitrotoluene decreases with decreases in reaction temperature. From 25 °C to –10 °C the amount of metanitrotoluene was less than for nitrating toluene by a nitric(V)acid/dichloromethane mixture than for nitration by 100% nitric(V) acid. Furthermore, from –20 °C to –30 °C results were similar with 2.6% of meta-nitrotoluene in the reaction products. An excess of nitric(V) acid in the nitration of toluene by the nitric(V) acid/dichloromethane mixture than in nitration by 100% nitric(V) acid. Nitration by the nitric(V) acid/dichloromethane mixture is less exothermic and easier to control than nitration by 100% nitric(V) acid.
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5-Fluoro-2-nitro-toluene was prepared from 3-fluorotoluene by three nitration processes: (1) nitration with mixed acid of HNO3-H2SO4 (in solvent, 36.2ml concentrated sulfuric acid, 14.8ml concentrated nitric acid, 0-5 V., 90g 3-fluorotoluene) giving a selectivity of 59.8% for 5-fluoro-2-nitro-toluene; (2) with mixed acid of 68%HNO3-H3PO4 (28.0ml 68% nitric acid, 0-51:, 35g polyphosphoric acid, 16.5g 3-fluorotoluene) giving a selectivity of 80.0%; (3) with concentrated nitric acid (96.5ml concentrated nitric acid, 200g 3-fluorotoluene, 50-55 ℃, 8 hours, distilled under vacuum) giving a selectivity of 79.9%. The product was characterized by 1H-NMR and IR.
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γ-Hexanitrohexaazaisowurtzitane(HNIW) was obtained with the yield of more than 88% and the purity of larger than 99.4% by nitration of tetraacetydiformylhexaazaisowurtzitane(TADFIW) in 82.48%-88.89% nitric acid.The results show that the optimal concentration of nitric acid is 86.66% as the yield is 94.0% and the purity is 99.51%.The main impurity pentanitromonoacetylhexaazaisowurtzitane(PNMAIW)in HNIW prepared by this method was seperated and characterized,that is different from the main impurity pentanitromonoformylhexaazaisowurtzitane (PNMFIW)in HNIW from nitration of TADFIW in the mixture of nitric acid and sulfuric acid.It shows that nitration mechanisms in those nitrating environments are different.
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Abstract Zur Untersuchung des Nitrierungsmechanismus von ungesättigten Verbindungen wurde als Nitrierungsobjekt N‐A1kenyl‐3,5‐dinitro‐1,2,4‐triazol (I) eingesetzt.
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When 4-methoxy-NNO-azoxybenzene [1 a] was kept in 20% nitric acid (HNO3-AcOH-H2O)at 40°C, 4-methoxy-ONN-4'-nitroazoxybenzene (6β) was obtained as a nitration product but the isomerization of 1α to 4-methoxy-ONN-azoxybenzene [1β] did not take place at all. In this reaction, 4-methoxy-NNO-4'-nitroazoxybenzene [6α] formed by para-nitration of 1α seems to isomerize to 6β immediately. However, neither nitration nor isomerization took place in the reaction of 1β with 20% nitric acid (HNO3-AcOH-H2O) under the similar reaction conditions. It is co nvenient method to obtain pure 1β that is the nitration of a mixtare 1α and 1β with dilute nitric acid under the mild conditions.
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Catalytic nitration of alkanes with nitric acid was first successfully achieved by the use of N-hydroxyphthalimide (NHPI) under mild conditions; the key to the present nitration was found to be the in situ generation of NO2 and phthalimide N-oxyl radical by the reaction of NHPI with nitric acid.
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