Mechanism of oxidation of iron(II) chelates by hexavalent chromium and heptavalent manganese in aqueous sulfuric acid and micellar media - a kinetic approach

Summary Oxidation of the Fe^II chelates [FeL] (L = phen or bipy) by Cr^VI and Mn^VII in H₂SO₄ medium was found to proceed through the formation of a bimetallic insertion complex which decomposes in the slow step, followed by electron transfer from [FeL] to the oxidant. The reactions are catalysed by both anionic and non-ionic micelles [SDS and triton-x (Tx), respectively]. A mechanism is suggested involving electrostatic stabilization of the cationic forms of the Fe^II chelates by anionic SDS and the partial anionic character of polyoxyethylene moiety of Tx, respectively. The marginal catalysis of cationic micelles (CTAB) is attributed to co-anion-micellar interactions.     

Micellar Mediated Halodecarboxylation of α,β‐Unsaturated Aliphatic and Aromatic Carboxylic Acids—A Novel Green Hunsdiecker–Borodin Reaction

A Novel Hunsdiecker‐Borodin reaction (HBR) has been carried out efficiently with α,β‐unsaturated aliphatic and aromatic carboxylic acids by using N‐halo succinimides such as N‐chloro succinimide (NCS), N‐bromo succinimide (NBS), and N‐iodo succinimide (NIS) under micellar media. The reaction with α,β‐unsaturated aromatic carboxylic acids afforded β‐halo styrenes in excellent yield while α,β‐unsaturated aliphatic carboxylic acids underwent decarboxylation and to give corresponding halo derivatives. The reactions are dramatically accelerated in micellar media. This procedure works efficiently in CTAB (cetyl trimethyl ammonium bromide), SDS (sodium dodecyl sulfate), and TX (Triton‐X‐100) media under stirred conditions at room temperature. At reflux temperatures the yield of reaction products were further enhanced from good to excellent.     

Kinetics and mechanism of certain benzoylation reactions under Vilsmeier–Haack conditions using benzamide and oxychloride in acetonitrile medium

Vilsmeier–Haack (VH) benzoylation reactions with benzaldehydes and acetophenones in acetonitrile medium obeyed second‐order reaction kinetics. Under kinetic conditions, the reactions afforded benzoyl derivatives irrespective of the nature of oxychloride (POCl₃ or SOCl₂) used for the preparation of VH reagent along with benzamide. The present finding is advantageous to understand the nature of reactive species as well as the mechanism of benzoylation. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 69–80, 2013     

Ultrasonically Assisted Rate Enhancements in Trichloroisocyanuric Acid/DMF/NaNO2 Triggered Nitration of Aromatic Compounds and Decarboxylative Nitration of α,β-Unsaturated Acids

An efficient and safe method for nitration of aromatic compounds and decarboxylative nitration of α,β-unsaturated acids was developed using trichloroisocyanuric acid (TCICA)/dimethylformamide (DMF) in the presence of NaNO₂. The reaction times of conventional protocol reduced from 8–10 h to 1.0–1.5 h (60–90 min) under sonication, even though the yields are comparable under both the conditions.     

Efficient and Facile Method for the Nitration of Aromatic Compounds by Nitric Acid in Micellar Media

Aromatic compounds were efficiently nitrated under mild reaction conditions by employing HNO₃ in the presence of anionic (sodium dodecyl sulfate, SDS), cationic (cetyl trimethyl ammonium bromide, CTAB), and nonionic (Triton-X 100) micelles. The reaction rapidly afforded corresponding mononitro derivatives in fair to good yields with high regioselectivity. This new method offers an environmentally safe reaction condition to minimize the waste products.     

Antimony Trioxide as an Efficient Lewis Acid Catalyst for the Synthesis of 5-Substituted 1H-Tetrazoles

Sb₂O₃ was found to be effective as a catalyst for a smooth (2 + 3) cycloaddition of sodium azide with nitriles to afford 5-substituted 1H-tetrazoles in good yields.     

Vilsmeier–Haack Bromination of Aromatic Compounds with KBr and N-Bromosuccinimide Under Solvent-Free Conditions

Bromination of aromatic hydrocarbons is triggered by Vilsmeier–Haack reagent [N,N-dimethyl formamide (DMF–POCl₃ system)] in the presence of KBr or N-bromosuccinimide (NBS) under solvent-free conditions by grinding the reactants in a mortar with a pestle. The reactions afforded corresponding bromo derivatives in very good yield with high regioselectivity. The results are comparable with those obtained under reflux conditions.     

Kinetics and Mechanism of Certain Acetylation Reactions with Acetamide/Oxychloride in Acetonitrile under Vilsmeier?Haack Conditions

Vilsmeier? Haack (VH) acetylation reactions with benzaldehydes or acetophenones in MeCN followed second‐order kinetics and afforded acetyl derivatives under kinetic conditions, irrespective of the nature of the oxychloride (SOCl₂ or POCl₃) used for the preparation of the VH reagent along with acetamide. The present finding contributes to the understanding of the nature of the reactive species of the VH reagent as well as of the acetylation mechanism.     

Polyethylene Glycol–Mediated Kinetic Study of Nitrodecarboxylation of α,β‐Unsaturated Acids by Blau's Fe(III) Bipy Complex

A kinetic and mechanistic study of nitro decarboxylation of α,β‐unsaturated acids (USA) has been taken up by Blau's yellow complex [Fe(III) nitrate–Bipy] in polyethylene glycol (PEG)–acetonitrile media. Kinetics of the reactions indicated a rate law: rate = ab[Fe (III)][Bipy][USA]/(1 + b [Bipy]), that represents the Michaelis–Menten type mechanism. Reaction rates are significantly influenced by the structural variation and concentration of PEG. The mechanism of PEG‐mediated reaction was explained through the formation of more active [PEG bound Fe(III) nitrate–Bipy species] than [Fe (III) nitrate–Bipy] itself. Formation of [PEG bound Fe(III) nitrate–Bipy species] could be due to the interaction of polyoxyethylene glycolate moiety with [Fe (III) nitrate–Bipy species] in the lines of nonionic micellar interactions.     

A kinetic study of the 1, 10-phenanthroline-catalysed iron(III) oxidation of epimeric aldo-, and D-, and L-ketohexoses

Summary Fe^III in H₂SO₄ medium does not oxidize sugars even at the reflux temperature, however, the reaction is catalysed by trace amounts of 1,10-phenanthroline (phen). A kinetic study shows that the oxidation rate increases as [phen] increases and exhibits a fractional order dependence upon [phen]. The orders with respect to [Fe^III] and [carbohydrate] are unity. The oxidation rate decreases as [HSO^4/–] and [H₂SO₄] increase. A plausible mechanism is proposed involving participation of an [Fe^III-phen] precursor and sugar in the rate-determining step.