Kinetics of Aromatic Nitration : the Nitronium Ion

Hughes, E. D.; Ingold, C. K.; Reed, R. I.

doi:10.1038/158448c0

Cited by 56 publications

(53 citation statements)

References 5 publications

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“…The IRC paths being determined to ensure the accuracy of the transition states involved in the reaction and the atomic coordinates of relevant stationary points are given in the Supporting Information (Figure S4 and Atomic Coordinates S5, respectively). As can be seen from Figures and , the hydrogen atoms on the carbon atoms in glyoxime are replaced successively by NO 2 + due to electrophilic substitutions; as a result, σ complexes with nitryl groups and hydrogen ions (H + ) are generated . The hydrogen ions (protons) are then captured by HNO 3 molecules to form the nitration products 3,4‐dinitroglyoxime and H 2 NO 3 + (H 2 O ⋅ NO 2 + ).…”

Section: Resultsmentioning

confidence: 99%

Reaction Mechanism of 3,4‐Dinitrofuroxan Formation from Glyoxime: Dehydrogenation and Cyclization of Oxime

et al. 2016

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The reaction pathway of the formation of 3,4-dinitrofuroxan from glyoxime is theoretically investigated under experimental conditions with 25 % nitric acid and dinitrogentetroxide reagents to clarify the mechanism of formation of a furoxan ring by glyoxime. The geometric configurations of minima and transition-state species are optimized at the (U)B3LYP/6-311++G** level. The CCSD(T) and CASSCF(10e,8o)/CASSCF(9e,8o) single-point energy corrections at the same level are performed on top of the optimized geometries. A subsequent dynamic correlation by using NEVPT2/6-311++G**-level single-point energy calculations based on the CASSCF results is also performed to obtain accurate energy values. The formation reaction is analyzed from two processes: glyoxime nitration and 3,4-dinitroglyoxime (nitration product) oxidative cyclization. Calculation results indicate that the electrophilic substitution of nitronium ions from the protonated HNO3 and the abstraction of hydrogen ions by HNO3 molecules are requisites of glyoxime nitration. The formation of a furoxan ring from 3,4-dinitroglyoxime involves two possible mechanisms: 1) oxydehydrogenation by NO2 molecules and the subsequent torsion of NO radical groups to form a ring and 2) the alternation of dehydrogenation and cyclization. The intermediates and transition states in both routes exhibit monoradical and diradical characteristics. Singlet and triplet reactions are considered for the diradical species. Results show that the singlet reaction mechanism is more favorable for cyclization than the triplet reaction. The formation of a furoxan ring from oxime is in accordance with the stepwise intermolecular dehydrogenation and intramolecular torsion to the ring.

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Section: Resultsmentioning

confidence: 99%

Reaction Mechanism of 3,4‐Dinitrofuroxan Formation from Glyoxime: Dehydrogenation and Cyclization of Oxime

et al. 2016

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“…According to the classic Ingold-Hughes nitration mechanism, [1][2][3][4][5][6][7]11,12] the first stage of benzene nitration (commonly described as rate-controlling) involves attack of NO 2 + , resulting in the formation of a s-complex (arenium ion or Pfeiffer-Witzinger-Wheland intermediate). [13][14][15] Thereaction then gives nitrobenzene by removal of the ipso proton from ArHNO 2 + by either the sulfuric acid or the bisulfate anion, HSO 4 À ,w hich both act as ab ase.Asingle electron transfer (SET) mechanism, widely considered as an alternative reaction path, involves the transfer of an electron from the aromatic ring to the nitronium ion;r ecombination of the resulting radical pair produces the same Whelandintermediate (ArHNO 2 + ).…”

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confidence: 99%

An Experimentally Established Key Intermediate in Benzene Nitration with Mixed Acid

et al. 2015

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Experimental evidence is reported for the first intermediate in the classic S E Ar reaction of benzene nitration with mixed acid. The UV/Vis spectroscopic investigation of the reaction showed an intense absorption at 320 nm (appearing as ab and shoulder) arising from ar eaction intermediate.O ur theoretical modeling shows that the interaction between the two principal reactants with solvent (H 2 SO 4 )m olecules significantly affects the structure of the initial complex. In this complex, al arger distance between the aromatic ring and nitronium ion precludes the possibility for electronic charge transfer from the benzene p-system to the electrophile.T he computational modeling of the potential energy surface reveals that the reaction favors astepwise mechanism with intermediate formation of p-a nd s-( arenium ion) complexes.

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“…In general, nitration reactions are fast and highly exothermic. Typically, the nitration of aromatic compounds is acid-catalyzed and it involves an electrophilic substitution where the nitronium ion (NO 2 + ) acts as the reactive species [4–6]. …”

Section: Introductionmentioning

confidence: 99%

Continuous flow nitration in miniaturized devices

Kulkarni¹

2014

Beilstein J. Org. Chem.

126

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SummaryThis review highlights the state of the art in the field of continuous flow nitration with miniaturized devices. Although nitration has been one of the oldest and most important unit reactions, the advent of miniaturized devices has paved the way for new opportunities to reconsider the conventional approach for exothermic and selectivity sensitive nitration reactions. Four different approaches to flow nitration with microreactors are presented herein and discussed in view of their advantages, limitations and applicability of the information towards scale-up. Selected recent patents that disclose scale-up methodologies for continuous flow nitration are also briefly reviewed.

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Kinetics of Aromatic Nitration : the Nitronium Ion

Cited by 56 publications

References 5 publications

Reaction Mechanism of 3,4‐Dinitrofuroxan Formation from Glyoxime: Dehydrogenation and Cyclization of Oxime

Reaction Mechanism of 3,4‐Dinitrofuroxan Formation from Glyoxime: Dehydrogenation and Cyclization of Oxime

An Experimentally Established Key Intermediate in Benzene Nitration with Mixed Acid

Continuous flow nitration in miniaturized devices

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