KOSEN 한인과학기술자네트워크

 A process for preparing semicarbazide hydrochloride comprising the steps:

(a) reacting an aqueous hydrazine solution with urea at a temperature from about 80° C. to about 130° C. and at a mole ratio of hydrazine to urea from about 0.9:1 to about 1.2:1 to form a reaction mixture comprising semicarbazide, water and alcohol-insoluble by-products;

(b) removing substantially all of the water from the reaction mixture;

(c) mixing a sufficient amount of an alcohol with the water-deleted reaction mixture to dissolve the semicarbazide and to precipitate said alcohol-insoluble by-products from the resulting alcohol solution;

(d) removing said precipitated alcohol-insoluble by-products from said alcohol solution;

(e) adding a sufficient amount of anhydrous hydrogen chloride to said alcohol solution to form and precipitate semicarbazide hydrochloride; and

(f) recovering said semicarbazide hydrochloride from said alcohol solution.

앞서 답변하신분이 언급하신 특허문헌은 US4482738의 청구항 부분입니다.

링크를 따라가면 엉뚱한 특허가 나옵니다. 정확한 링크는 다음과 같습니다.

http://www.patentstorm.us/patents/4482738/fulltext.html

끝 부분의 Example 1을 참고하시면 됩니다.

EXAMPLE I

Use of Anhydrous Acid Conditions

Urea (60.1 g, 1 mole) and 64% aqueous hydrazine solution (55 g, 1.10 moles) were placed in a 250 ml, 3-neck flask and heated at reflux (115°-120° C.) for three hours evolving gaseous ammonia. At the end of the reaction period, theexcess hydrazine and accompanying water were vacuum stripped at 70° C. and 10 torr, leaving semicarbazide and by-products including hydrazodicarbonamide. These were separated by digesting in 200 ml of boiling methanol for 45 minutes andfiltering off the insoluble hydrazodicarbonamide (5.5 g). The filtrate was cooled to 10° C. and a solution of 37 g (one mole) of anhydrous hydrogen chloride in 65 ml of methanol added. The product precipitated, was filtered off, washed with 50ml of methanol and dried to give 100 g of semicarbazide hydrochloride--89.7% of theory based on urea charged and assaying 97.6% by NaOH titration.

Comparison I

Use Of Aqueous Acid Conditions

Urea and 64% hydrazine were reacted on the same scale and conditions as in Example I, except that after digesting the mixture and filtering away the hydrazodicarbonamide, 98 g of 37% aqueous hydrochloric acid (1 mole) was added to precipitate thesemicarbazide hydrochloride. The product was filtered from the methanol/water solution, washed with methanol and dried to give 86.2 g, which represents 77.3% of theory based on urea charged and assaying 97.8% pure by NaOH titration.

Comparing the product yield of Example I to Comparison I, one can readily see that the process of the present invention produces a significantly higher yield.

Other References

• Charles Clark, Hydrazine, Mathieson Chemical Corporation, pp. 59-63, (1953)
• Mistry et al., J. Ind. Chem. Soc., vol. 7, p. 793, (1930)
• Das-Gupta, J. Ind. Chem. Soc., vol. 10, p. 111, (1933)
• Wheeler, JACS, 51, 3654, (1929)