1‐Amino‐2‐methylindoline is a precursor used in the synthesis of antihypertension drugs. It reacts with monochloramine to lead to the formation of 1‐amino‐2‐methylindole and azo(2‐methyl)indoline. These new products have been isolated and characterized by microanalysis, uv, gc/ms, ir, and 1H/13C nmr. The reaction leads to the transient formation of an indolic aminonitrene. 1‐Amino‐2‐methylindole formation proceeds in strongly alkaline medium by rearrangement of a diaziridine intermediate. In neutral or slightly alkaline medium, one obtains a precipitate of tetrazene type (‐N‐N=N‐N‐), the azo(2‐methyl)indoline. The study of the thermochemical properties shows that tetrazene decomposes towards 150 °C to give the 1,1′‐bi(2‐methyl)indoline. The stability of the starting reagents and products was the subject of a systematic investigation. A reaction mechanism is proposed.

The kinetics of the Cl-transfer reaction between chloramine (1) and piperidine (2) in a Raschig medium (8 < pH < 9) was studied at various temperatures, with variable concentrations of the two reactants. The influence of the pH on the interaction of 1 and 2 was examined at a pH ranging between 8.25 and 12.89. The Cl-transfer reaction resulted in the formation of 1-chloropiperidine (3), which, in the presence of NaOH, underwent a dehydrohalogenation leading to an endocyclic imine derivative: 2,3,4,5-tetrahydropyridine (4). The kinetics of the dehydrohalogenation was also studied at different temperatures, with variable concentrations of 3 and NaOH. Kinetic and thermodynamic parameters were determined for the Cl-transfer and dehydrohalogenation reactions. Both 3 and 4 were prepared according to efficient synthetic routes; they were isolated, purified, and characterized by elemental analysis, IR, 1 H-and 13 C-NMR, and MS. Their thermal stabilities were evaluated by differential scanning calorimetry (DSC), and their absorption coefficients at various wavelengths were determined experimentally by UV spectrophotometry.

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The kinetics of the oxidation of N-aminopiperidine with chloramine was studied at different temperatures, with variable concentrations of the two reactants and at a pH ranging between 12 and 13.5. The reaction showed to be involving two steps: the first corresponded to the formation of a diazene intermediate, the second to the evolution of this intermediate into numerous compounds within a complex reactional chain. The rate law of the first step was determined by the Ostwald method and 2 found to be first order with respect to each reactant. The rate constant was determined at pH = 12.89 and T = 25°C: k 2 = 1.15 × 10 5 exp(-39/RT) M -1 s -1 (E 2 in kJ mol -1 )With decreasing pH value, the first step exhibited acid catalysis phenomena, and diazene was converted into azopiperidine particularly faster. This created overlapping UV-absorptions between chloramine and azopiperidine, also observed in HPLC. GC/MS analyses were used to identify some of the numerous by-products formed. Their proportions are dependent of both pH and the reactants' concentrations ratio. A reaction mechanism taking this relationship into account, was suggested.

High-grade chloramine is prepared in batch and in continuous mode starting from mixed ammoniacal solutions and hypochlorite at hundred chlorometric degrees.