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Synthesis of Diazoethane

William Dampier

Well-known member
Jul 19, 2021
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0. Safety Rules

All work must be carried out in strict accordance with the techniques and necessarily in the exhaust cabinet. Sodium nitrite and its solutions, nitrosyl helic acid should be added in small portions to avoid the rapid release of nitrogen oxides and under constant cooling. Remember that the nitrogen oxide standing in diazoting can cause suffocations, the burns of the mucous membranes, and with long-term inhalation in large concentrations - pulmonary edema. The obtained diazonium salts are explosive in a dry form, but in order to avoid the explosion, they cannot be left for a long time even in solutions. In the preparation of the compounds according to the reactions of diazonium salts, accompanied by the co-release of nitrogen, the addition of reactants should be done slowly and in small portions. Azocrasers are absorbed through the skin and can cause poisoning. If poisoning, azo dyes may cause headaches, slight fever, increased heart rate. With constant work with azocrase, dermatitis is observed, so work must be performed in protective gloves. Alkylnitrics are toxic compounds that cause extension of vessels, which can manifest itself in redness of the skin. Diazoethane - poisonous yellow gas that can explode.

1. N-ethyl-N-nitrosourea

Ethylamine HCl - 100 g,
Urea - 250 g,
NaNO2 - 90 g,
conc.H2SO4 - 50 ml.

Round Bottom flask - 2000 ml,
Round Bottom Еhree-Тecked flask - 3000 ml,
Reflux condenser,
Drip funnel,
Mechanical mixer,

100 g of ethylamine hydrochloride and 250 g of urea were dissolved in 400 ml of water and boiled at low heat for 3 hours. The solution was then transferred to a three-necked 3 liters flask equipped with a dropping funnel, a thermometer and a mechanical stirrer and added 110 grams of NaNO2. The contents of the flask are cooled to -10 *C and the solution of 50 ml of H2SO4 in 600 ml of water is added dropwise, maintaining the temperature of the mixture with an external cooling, which is not higher than 5 *C. After completion of the addition of sulfuric acid, the crystals formed are N-ethyl-N-nitrosourea were filtered off and washed with cold water. The resulting crystals are dried in vacuo at room temperature. Yield 100 g. The resulting drug can be stored in a refrigerator a fairly long period of time.

2. Diazoethane

N-ethyl-N-nitrosourea - 10 g,
KOH 40% aq. soln. - 30 ml,
Diethyl ether - 100 ml,
KOH solid.

Erlenmeyer flask,
Magnetic stirrer,
Separating funnel,

To obtain a solution of diazoethane in an Erlenmeyer flask, equipped with a magnetic stirrer in teflon and a thermometer, 100 ml of ether and 30 ml of 40% of the aqueous KOH solution are placed. The solution is cooled to 0*C with a mixture of ice with salt and with continuous transfer in small portions 10 g of nitrosoethylurea, maintaining the temperature not higher than +5*C. After the reaction, the organic layer was separated by decantation and dried over solid KOH. The yield of diazoetane is 60%.
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New member
Apr 29, 2022
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Thank you so much Dampier for this write-up. Where does one go about getting "N-ethyl-N-nitrosourea - 10 g," or can it be replaced?