Oxazoline‐terminated macromonomers by the alkylation of 2‐methyl‐2‐oxazoline

Well‐defined macromonomers of poly(ethylene oxide) and poly(tert‐butyl methacrylate) were obtained by anionic polymerization induced directly by the carbanion issued from 2‐methyl‐2‐oxazoline. When ethylene oxide was added to this carbanion with lithium as the counterion, a new compound able to initiate the polymerization of ε‐caprolactone in an anionically coordinated way was synthesized, and this led to well‐defined poly(ε‐caprolactone) macromonomers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2440–2447, 2005     

Kinetic studies on the reactions of 3‐isothiazolones with 2‐methyl‐2‐propanethiol

The kinetics of the ring‐opening reactions of the 3‐isothiazolones ( 1a–d ) with aqueous 2‐methyl‐2‐propanethiol has been explored at pH 4. The results strongly suggest that the reaction is second order in thiol and third order overall. Extrapolation of the kinetic data gives third‐order rate constants that lie in the order ( 1a ) > ( 1b ) > ( 1c ) > ( 1d ) in line with the known biological activity of these derivatives. The mechanism of the reaction is thought to involve attack by one thiol at the sulfur atom of the isothiazolone with the concomitant hydrogen bonding of a second thiol to the amide nitrogen. Calculations of the structure and electronic properties of the isothiazolones at the RHF 6‐31G** level are supportive. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 254–260, 2005     

Synthesis of hydroxyethylhydrazine by the Raschig process and comparison with synthesis by the alkylation process

The Raschig synthesis of hydroxyethylhydrazine (HEH) is studied, that is, the reaction of monochloramine on ethanolamine. The formation of HEH is monitored by UV spectrometry, and the influence of temperature and pH is studied. The primary reaction is an SN₂‐type mechanism, whereas the main secondary reaction is the oxidation of HEH by monochloramine. This reaction is also monitored by UV spectrometry, and the oxidation product is identified by GC–MS analysis, showing the formation of hydroxyethylhydrazone. The reaction mechanisms and the rate constants were determined, and the results permit establishing the main reactions occurring during HEH synthesis. These reactions were validated in a concentrated medium, with the systematic study of the influence of the molar ratio p ([HEH]₀/[NH₂Cl]₀) and the final sodium hydroxide concentration and temperature. A comparison is made with the other synthesis process already published, that is, the alkylation of hydrazine by either chloroethanol or epoxide. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 331–344, 2011     

Kinetic and mechanistic studies on the oxidation of Norfloxacin by Chloramine‐B and N‐Chlorobenzotriazole in acidic medium

The kinetics of oxidation of Norfloxacin [1‐ethyl‐6‐fluoro‐1,4‐dihydro‐4‐oxo‐7‐(l‐piperazinyl)‐3‐quinoline carboxylic acid] by chloramine‐B and N‐chlorobenzotriazole has been studied in aqueous acetic acid medium (25% v/v) in the presence of perchloric acid at 323 K. For both the oxidants, the reaction follows a first‐order dependence on [oxidant], a fractional‐order on [Norfloxacin], and an inverse‐fractional order on [H⁺]. Dependence of reaction rate on ionic strength, reaction product, dielectric constant, solvent isotope, and temperature is studied. Kinetic parameters are evaluated. The reaction products are identified. The proposed reaction mechanism and the derived rate equation are consistent with the observed kinetic data. Formation and decomposition constants for substrate–oxidant complexes are evaluated. ©1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 153–158, 1999     

Kinetic study of the nitrosation of 1,3‐dialkylureas in aqueous‐perchloric acid medium

The kinetics of the nitrosation of 1,3‐dimethyl (DMU), 1,3‐diethyl (DEU), 1,3‐dipropylurea (DPU), 1,3‐dibuthyl (DBU), and 1,3‐diallylurea (DAU) were studied in a conventional UV/vis spectrophotometer in aqueous‐perchloric acid media. The kinetic study was carried out using the initial rate method. The reaction rate observed was where K_a is the acidity constant of nitrous acid. The diureas exhibited the reactivity order DMU ? DEU > DPU > DAU, which can be interpreted as a function of the steric impediment generated by the R alkyl group in the rate controlling step. A probable relationship between both the chemical reactivity and structure of the nitrosable substrate with the biological activity of the N‐nitroso compounds generated is proposed. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 273–279, 2004     

Kinetic studies and mechanism on the permanganic oxidation of L‐Glutamine in strong acid medium in the presence and absence of Silver (I)

The kinetic study and mechanism of the permanganic oxidation of L‐glutamine in sulfuric acid has been carried out both in the absence and presence of silver (I) using a spectrophotometric technique. Activation parameters have been evaluated using the Arrhenius and Eyring plots. Mechanisms consistent with the observed kinetic data have been proposed and discussed. The overall rate expression for the oxidation may be written as In the presence of silver (I) the rate law is The reaction appears to involve an acid catalyzed and data showed role of water molecules in the rate‐determining step is proton transfer which satisfies Bunnett's theory. A mechanism satisfying the various kinetic parameters has been proposed. ©1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 95–102, 1999     

Kinetic study of 2‐furanaldehyde, 3‐furanaldehyde,and 5‐methyl‐2‐furanaldehyde reactions initiated by Cl atoms

Rate coefficients for the gas‐phase reactions of chlorine atoms with a series of furanaldehydes have been determined at 298 ± 2 K and atmospheric pressure (708.5 ± 0.1). The experiments were performed using the relative technique combined with solid‐phase microextraction (SPME) sampling and gas chromatography with flame ionization detection (GC‐FID). Rate constants were determined relative to the reaction of Cl with n‐nonane and 2‐ethylfuran. The absolute rate coefficients k (in units of 10^?10 cm³ molecule^?1 s^?1) obtained were 2.61 ± 0.27 for 2‐furaldehyde, 3.15 ± 0.27 for 3‐furaldehyde, and 4 ± 0.5 for 5‐methyl‐2‐furaldehyde. This study shows that the reactions of furanaldehydes and Cl are very fast with little influence of the position of the aldehyde group or the presence of other substituent on the reactivity. The results seem to indicate a mechanism involving two main reaction channels, addition of chlorine atom to the double bond of the aromatic ring, and the abstraction of the aldehydic hydrogen. Further product studies are necessary to determine the mechanism of these reactions in more detail. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 670–678, 2008     

Regioselective synthesis of 1,2,4‐triazol‐3(2H)‐ones and their 3(2H)‐thiones: Kinetic studies and selective pyrolytic deprotection

Selective pyrolytic deprotection of 2‐ethyl and 2‐cyanoethyl‐4‐arylidenimino‐1,2,4‐triazol‐3(2H)‐ones and their 3(2H)‐thiones was studied by flash vacuum pyrolysis. This study is useful in regioselective synthesis of 2‐ and 4‐substituted 1,2,4‐triazoles of potential biological applications. The kinetic results and product analysis lend support to a reaction pathway involving a six‐membered transition state. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:50–55, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10086     

Kinetic studies of the self‐reaction and reaction with HO2 of a tertiary β‐brominated peroxy radical between 298 and 393 K

The kinetics of reactions of the tertiary β‐brominated peroxy radical BrC(CH₃)₂C(CH₃)₂O₂ (2‐bromo‐1,1,2‐trimethylpropylperoxy) have been studied using the laser flash photolysis technique, photolysing HBr at 248 nm in the presence of O₂ and 2,3‐dimethylbut‐2‐ene. At room temperature, a rate constant of (2.0 ± 0.8) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹ was determined for the BrC(CH₃)₂C(CH₃)₂O₂ self‐reaction. The reaction of BrC(CH₃)₂C(CH₃)₂O₂ with HO₂ was investigated in the temperature range 306–393 K, yielding the following Arrhenius expression: k(BrC(CH₃)₂C(CH₃)₂O₂ + HO₂) = (2.04 ± 0.25) × 10⁻¹² exp[(501 ± 36)K/T] cm³ molecule⁻¹ s⁻¹, giving by extrapolation (1.10 ± 0.13) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ at 298 K. These results confirm the enhancement of the peroxy radical self‐reaction reactivity upon β‐substitution, which is similar for Br and OH substituents. In contrast, no significant effect of substituent has been observed on the rate constant for the reactions of peroxy radicals with HO₂. The global uncertainty factors on rate constants are equal to nearly 2 for the self‐reaction and to 1.35 for the reaction with HO₂. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 33: 41–48, 2001     

Gas‐phase pyrolysis of 2‐heteroaromatic‐1‐dimethylaminoethylenes: Kinetic and mechanistic study

Gas‐phase pyrolysis reactions of 4(2′‐dimethylaminoethenyl)‐2‐oxo‐2H‐benzo[b]pyran‐3‐carbonitrile ( 1 ), 4(2′‐dimethylaminoethenyl)‐2‐oxo‐2H‐naphtho[1,2‐b]pyran‐3‐carbonitrile ( 2 ), 1,6‐dihydro‐4‐(2′‐dimethylaminoethenyl)‐6‐oxo‐1‐phenylpyridazine‐3,5‐dicarbonitrile ( 3 ), 2‐cyano‐5‐dimethylamino‐3‐phenyl‐2,4‐pentadienonitrile ( 4 ), 2‐cyano‐5‐dimethylamino‐3‐(2‐thienyl)‐2,4‐pentadienonitrile( 5 ), 1,2‐dihydro‐4‐(2′‐dimethylaminoethenyl)‐oxo‐quinoline‐4‐carbonitrile ( 6 ), 6‐(ethylthio)‐4‐(2′‐dimethylaminoethenyl)‐2‐phenylpyrimidine‐5‐carbonitrile ( 7 ) (Scheme 1) have been carried out. The rates of gas‐phase pyrolytic reactions of compounds 3, 4, 5, and 7 have been measured and found to correspond to unimolecular first‐order reactions. Product analyses together with kinetic data were used to outline a feasible pathway for the pyrolytic reactions of the compounds under study. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:47–51, 2001     

Kinetic and mechanistic studies of some aliphatic amines' oxidation by sodium N‐bromo‐p‐toluenesulfonamide in hydrochloric acid medium

Oxidations of n‐propyl, n‐butyl, isobutyl, and isoamyl amines by bromamine‐T (BAT) in HCl medium have been kinetically studied at 30°C. The reaction rate shows a first‐order dependence on [BAT], a fractional‐order dependence on [amine], and an inverse fractional‐order dependence on [HCl]. The additions of halide ions and the reduction product of BAT, p‐toluenesulfonamide, have no effect on the reaction rate. The variation of ionic strength of the medium has no influence on the reaction. Activation parameters have been evaluated from the Arrhenius and Eyring plots. Mechanisms consistent with the preceding kinetic data have been proposed. The protonation constant of monobromamine‐T has been evaluated to be 48 ± 1. A Taft linear free‐energy relationship is observed for the reaction with ρ* = −12.6, indicating that the electron‐donating groups enhance the reaction rate. An isokinetic relationship is observed with β = 350 K, indicating that enthalpy factors control the reaction rate. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 776–783, 2000     

Experimental and quantum chemical calculational studies on N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐hydrazine

The title molecule, N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐ hydrazine (C₂₀ H₂₀ N₄ S₁), was characterized by ¹H‐NMR, ¹³C‐NMR, IR, UV‐visible, and X‐ray determination. In addition to the molecular geometry from X‐ray experiment, the molecular geometry, vibrational frequencies and gauge including atomic orbital ¹H‐ and ¹³C‐NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree‐Fock and density functional method (B3LYP) with 6‐31G(d, p) basis set. The calculated results show that optimized geometries can well reproduce the crystal structural parameters. By using time‐dependent density functional theory method, electronic absorption spectrum of the title compound has been predicted. © 2011 Wiley Periodicals, Inc.     

A novel synthesis of 5‐aryl‐3‐phenylpyrazole from 2‐aryl‐3‐benzoyl‐1,1‐cyclopropanedicarbonitrile and hydrazine

A new process for synthesis of 5‐aryl‐3‐phenylpyrazole is achieved. The regioselective ring‐opening reaction of 2‐aryl‐3‐benzoyl‐1,1‐cyclopropanedicarbonitrile with hydrazine plays a crucial role in the described process.     

The reaction of 2‐phenoxy‐3,5‐dinitropyridine with substituted anilines in the presence of 1,4‐diazabicyclo[2.2.2]octane in dimethyl sulfoxide: Kinetic and equilibrium studies

The reactions of 2‐phenoxy‐3,5‐dinitropyridine ( 1 ) with a series of substituted anilines ( 4a–d ) in dimethyl sulfoxide (DMSO) in the presence of 1,4‐diazabicyclo[2.2.2]octane (DABCO) yield the 2‐anilino derivatives without the accumulation of intermediates. The kinetics is compatible with a two‐step reaction involving initial nucleophilic attack followed by either base‐catalyzed or uncatalyzed conversion to the product. The base‐catalyzed pathway is likely to involve rate‐limiting proton transfer from the zwitterionic intermediate to base. The results are compared with those for reactions of 1,3,5‐trinitrobenzene (2) and phenyl 2,4,6‐trinitrophenyl ether ( 3 , R = Ph ) with anilines. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 198–203, 2009     

Kinetic study of the interaction of adenosine 5′‐monophosphate with diaqua (2‐hydrazinopyridine) palladium(II) in aqueous medium

The interaction of the palladium(II) complex [Pd(hzpy)(H₂O)₂]²⁺, where hzpy is 2‐hydrazinopyridine, with purine nucleoside adenosine 5′‐monophosphate (5′‐AMP) was studied kinetically under pseudo‐first‐order conditions, using stopped‐flow techniques. The reaction was found to take place in two consecutive reaction steps, which are both dependent on the actual 5′‐AMP concentration. The activation parameters for the two reaction steps, i.e. ΔH = 32 ±2 kJ mol^?1, ΔS = ?168 ±7 J K^?1 mol^?1, and ΔH = 28 ± 1 kJ mol^?1, ΔS = ?126 ± 5 J K^?1 mol^?1, respectively, were evaluated and suggested an associative mode of activation for both substitution processes. The stability constants and the associated speciation diagram of the complexes were also determined potentiometrically. The isolated solid complex was characterized by C, H, and N elemental analyses, IR, magnetic, and molar conductance measurements. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 132–142, 2010     

Kinetic characterization of a transient reaction by degeneration of the precursor mechanism: Application to the synthesis of 3,4‐diazabicyclo[4.3.0]‐ non‐2‐ene

The rate of the oxidation of N‐amino‐3‐azabicyclo[3.3.0]octane by chloramine has been studied by GC and HPLC between pH 10.5 and 13.5. The second‐order reaction exhibits specific acid catalysis. The formation of N,N′‐azo‐3‐azabicyclo[3.3.0]octane or 3,4‐diazabicyclo[4.3.0]non‐2‐ene is pH, concentration, and temperature dependent. In alkaline media, the exclusive formation of 3,4‐diazabicyclo[4.3.0]non‐2‐ene is observed. Kinetic studies show that the oxidation of N‐amino‐3‐azabicyclo[3.3.0]octane by chloramine is a multistep process with the initial formation of a diazene‐type intermediate, which is converted by hydroxide ions into 3,4‐diazabicyclo[4.3.0]non‐2‐ene. Because it was not possible to follow the rate of change of the intermediate concentration, to determine the kinetics of 3,4‐diazabicyclo[4.3.0]non‐2‐ene formation, a procedure based on the degeneration of the precursor process was adopted. An appropriate mathematical treatment allowed a quantitative interpretation of all the phenomena observed over the given pH interval. The activation parameters were determined. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 327–338, 2006     

Reactivity studies of ethyl(Z)‐N‐(2‐amino‐1,2‐dicyanovinyl) formimidate with carbonyl compounds in the presence of base

The reaction of ethyl(Z)‐N‐(2‐amino‐1,2‐dicyanovinyl)formimidate 6 with carbonyl compounds in the presence of triethyl amine occurs with formation of the Schiff s base and intramolecular hydrolysis of the adjacent cyano group to give the alkylideneamino derivatives 8a‐f . When the α‐carbon of the ketone has at least one proton, the prolonged contact of 8a‐f with triethylamine causes intramolecular cyclization between this carbon and the imidate carbon atom to form a seven membered ring. This is followed by cyclization of the cyano and amido groups, leading to the pyrrolo[4,3‐b][1,4]diazepines 9 . If a strong base is used the first ring to be formed is the pyrrole ring as evidenced in the reaction of 8a with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene leading to 14 . The subsequent addition of methyl amine to the reaction mixture, caused cleavage of the alkylideneamino unit and formation of the amidine function from the imi date ( 15 ). The addition of acid to the imidates 8a and 8f led to the diazepine compounds 10a and 10f respectively. A suspension of compound 8e in ethanol and triethylamine evolved to a pyrazinone structure 12 under kinetic conditions (4 hours, room temperature) and to the pyrrolo[4,3‐b][1,4]diazepine 9e under thermodynamic conditions (48 hours, room temperature).