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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

To optimize yields, the study of reaction kinetics related to the synthesis of 2-hydroxyethylhydrazine (HEH) obtained from the alkylation of N2H4 by 2-chloroethanol (CletOH) was carried out with and without sodium hydroxide. In both cases, the main reaction of HEH formation was followed by a consecutive, parallel reaction of HEH alkylation (or dialkylation of N2H4), leading to the formation of two isomers: 1,1-di(hydroxyethyl)hydrazine and 1,2-di(hydroxyethyl)hydrazine. In this study, hydrazine and hydroxyalkylhydrazine alkylations followed SN2 reactions triggered directly by CletOH or indirectly in the presence of a strong base by ethylene oxide, an intermediate compound. The kinetics was studied in diluted mediums by quantifying HEH and CletOH by gas chromatography and gas chromatography coupled with mass spectrometry (GC-MS). The activation parameters of each reaction and the influence of a strong base present in the medium on the reaction mechanisms were established. A global mathematical treatment was applied for each alternative. It allowed modeling the reactions as a function of reagent concentrations and temperature. In the case of direct alkylation by CletOH, simulation was established for semi-batch and batch syntheses and was confirmed in experiments for concentrated mediums (1.0 M ≤ [CletOH]0 ≤ 3.2 M and 15.7 M ≤ [N2H4]0 ≤ 18.8 M). Simulation therefore permits the prediction of the instantaneous concentration of reagents and products, in particular ethylene oxide concentration in the case of indirect alkylation, which must be as weak as possible. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 382–393, 2009

After an exhaustive study of the system ammonia–dimethylchloramine in liquid ammonia, it was interesting to compare the reactivity of this system in liquid ammonia with the same system in an aqueous medium. Dimethylchloramine prepared in a pure state undergoes dehydrohalogenation in an alkaline medium: the principal products formed are N-methylmethanimine, 1,3,5-trimethylhexahydrotriazine, formaldehyde, and methylamine. The kinetics of this reaction was studied by UV, GC, and HPLC as a function of temperature, initial concentrations of sodium hydroxide, and chlorinated derivative. The reaction is of the second order and obeys an E2 mechanism (k1 = 4.2 × 10−5 M−1 s−1, ΔH○# = 82 kJ mol−1, ΔS○# = −59 J mol−1 K−1). The oxidation of unsymmetrical dimethylhydrazine by dimethylchloramine involves two consecutive processes. The first step follows a first-order law with respect to haloamine and hydrazine, leading to the formation of an aminonitrene intermediate (k2 = 150 × 10−5 M−1 s−1). The second step corresponds to the conversion of aminonitrene into formaldehyde dimethylhydrazone at pH 13). This reaction follows a first-order law (k3 = 23.5 × 10−5 s−1). The dimethylchloramine–ammonia interaction corresponds to a SN2 bimolecular mechanism (k4 = 0.9 × 10−5 M−1 s−1, pH 13, and T = 25°C). The kinetic model formulated on the basis of the above reactions shows that the formation of the hydrazine in an aqueous medium comes under strong competition from the dehydrohalogenation of dimethylchloramine and the oxidation of the hydrazine formed by the original chlorinated derivative. A global model that explains the mechanisms both in an anhydrous and in an aqueous medium was elaborated. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 340–351, 2008

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

The synthesis of 1-amino-2-methylindoline by the Raschig process was undertaken in aqueous solution. The principal side reaction that occurs in the medium is the oxidation of 1-amino-2-methylindoline formed by chloramine. To increase the yield of 1-amino-2-methylindoline, its oxidation by chloramine was studied by GC and HPLC at various concentrations of reactants and for a pH interval ranging between 9.9 and 13.5. The reaction is bimolecular and exhibits a specific acid catalysis. In alkaline medium, 1-amino-2-methylindole is the principal product. The enthalpy and entropy of activation were determined at pH 12.89. In unbuffered solution, the interaction was autocatalyzed by the ammonium ions formed, which indicates a competitive oxidation of neutral and ionic forms of 1-amino-2-methylindoline by chloramine. A mathematical treatment based on one implicit equation allows a quantitative interpretation of all the phenomena observed over the above pH interval. It takes both acid–base dissociation equilibrium and alkaline hydrolysis of chloramine into account. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 515–523, 2002

The reaction between chloramine and 2-methylindoline was studied at pH 12.89, T = 40°C, and for different initial concentrations of reactants. The interaction includes two concurrent bimolecular mechanisms leading to 1-amino-2-methylindoline and 2-methylindole. The rate laws were determined at the first moments of the reaction by using a differential method. By considering the totality of the reactions that occur in the medium, an appropriate mathematical model was developed. It permits to follow the evolution of the system over time and to calculate the final yields of reaction products. An optimization in terms of the initial contents of 2-methylindoline and chloramine was performed. It indicated that the maximum yield of 1-amino-2-methylindoline does not exceed 56%. The results show the limit of the Raschig process for the synthesis of indolic hydrazines in aqueous medium. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 575–584, 2002

The formation of 3-azabicyclo[3,3,0]oct-2-ene in the course of the synthesis of N-amino-3-azabicyclo[3,3,0]octane using the Raschig process results from the following two consecutive reactions: chlorine transfer between the monochloramine and the 3-azabicyclo[3,3,0]octane followed by a dehydrohalogenation of the substituted haloamine. The kinetics of the reaction were studied by HPLC and UV as a function of temperature (15 to 44°C), and the concentrations of NaOH (0.1 to 1 M) and the chlorinated derivative (1 to 4×10−3 M). The reaction is bimolecular (k=103×10−6 M−1 s−1; ΔH0#=89 kJ mol−1; and ΔS0#=−33.6 J mol−1 K−1) and has an E2 mechanism. The spectral data of 3-azabicyclo[3,3,0]oct-2-ene were determined. IR, NMR, and ES/MS analysis show dimerization of the water-soluble monomer into a white insoluble dimer. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 129–136, 1998.