TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: A mole ratio of the oxidizing agent to (II) is 2-2.05, preferably 2. The aqueous reaction medium is water. (II) is used in the form of an aqueous solution having a mass weight of 20-100%, preferably 30-60% or 36%. The oxidizing agent is used in the form of an aqueous solution of 48-55 colorimetric degrees. A catalyst of the catalytic hydrogenation is rhodium on coal or raney nickel.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The reaction step is carried out at a temperature of 20-70 degrees C, preferably of 20-40 degrees C. The catalytic hydrogenation is carried out at a hydrogen pressure of 1-65 bars, preferably 35 bars and at a temperature of 10-80 degrees C, preferably 60 degrees C. The isolating step includes: decomposition of the reaction medium obtained after the catalytic hydrogenation by the addition of sodium hydroxide in the reaction medium; and isolating (I) contained in an organic phase after the decomposition of the reaction medium. The sodium hydroxide is in the form of an aqueous solution having a mass of 40-50 wt.%. The decomposition step is carried out at a temperature of 15-50 degrees C, preferably 20 degrees C under an inert atmosphere. The isolating step is carried out under reduced pressure. Preferred Components: (II) is 1,3-diaminopropane or 1,4-diaminobutane. EXAMPLE - 35.6 g of 1.3-Diaminopropane and 61.5 g of water were introduced into a reactor at 25 degrees C. A volume of 391 ml of sodium hypochlorite maintained at the same temperature was added drop by drop in the reactor for 1 hour and 40 minutes. The temperature during the addition of the sodium hypochlorite was 25-30 degrees C. The reaction mixture was analyzed using gas chromatography-mass spectrometry and UV to obtain 74% of 1-pyrazoline and 18% of 2-pyrazoline. 180 ml of Reaction mixture was introduced into a hydrogenation reactor, in which 0.55 g of rhodium on coal was added. Hydrogenation was carried out at 60 degrees C under a pressure of 35 bars for 4 hours. 60g of Soda ash was added into the reaction mixture to concentrate the pyrazolidine in a light organic phase at a temperature of 25 degrees C and under inert gas (nitrogen gas) to avoid the oxidation of pyrazolidine in 1-pyrazoline. After filtration of the precipitated sodium chloride, the decomposition in two phases was observed. After extraction and elimination of the aqueous phase, the organic phase was distilled under reduced pressure (227 mmHg, 0.3 bar) to obtain pyrazolidine with purity of 98.3%.