Kinetic studies of hydrazine and 2‐hydroxyethylhydrazine alkylation by 2‐chloroethanol: Influence of a strong base in the medium

Abstract

To optimize yields, the study of reaction kinetics related to the synthesis of 2-hydroxyethylhydrazine (HEH) obtained from the alkylation of N 2 H 4 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 N 2 H 4 ), 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 S N 2 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 ≤ [N 2 H 4 ] 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.

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

“…Under these conditions, the NH 2 Cl rate is almost quantitative and the resulting solution concentration is equal to 1.04 M (B 1 ) for NH 2 Cl and 0.1 M (B 2 ) for NH 4 Cl.…”

“…The other reagents and salts used in this study (NaOH, NH 4 Cl, Na 2 HPO 4 , KH 2 PO 4 , etc.) were products for analysis at +99% (reagents from Prolabo RP, Merck, Aldrich, etc.…”

“…The following compounds: NH 2 Cl, NH 4 Cl, HO-(CH 2 ) 2 -NH 2 , NaOH, and HO-(CH 2 ) 2 -NH-NH 2 are, respectively, represented by indices from 1 to 5. Consequently, the molecular weights and densities of the reagents and resulting solutions are, respectively, represented by the symbols M i and d i .…”

“…• chlorometry) with a mixed ammonia solution NH 3 /NH 4 Cl (25 mL, 3.6 M/2.38 M) in the presence of ethyl ether (40 mL). For the kinetic studies, NH 2 Cl was purified by successive extractions with water and then stored at 5…”

“…In a previous paper [4], HEH was synthesized by alkylation of N 2 H 4 with 2-chloroethanol (CletOH) with or without a strong base. Another widely used method is the Raschig process.…”