PUTRESCINE DIHYDROCHLORIDE

B. Putrescine dihydrochloride. A 2-1. wide-mouthed Erlen-meyer flask containing 200 ml. of concentrated hydrochloric acid and 400 g. of cracked ice is clamped in an ice-salt bath and provided with an efficient stirrer (inefficient stirring may lower the yield). The stirring is started, and 80 g. (0.46 mole) of adipyl hydrazide is added all at once, followed by 500 ml. of ether (Note 5). While the temperature is maintained below 10° (Note 6), a solution of 80 g. (1.15 moles) of sodium nitrite in 150 ml. of water is added over about 30 minutes through a dropping funnel whose stem reaches below the bottom of the ether layer, but not into the path of the stirrer. The operations in the next paragraph should be conducted without delay after the completion of the addition of the nitrite. 

The residue of crystalline putrescine dihydrochloride is rinsed onto a Buchner funnel with the aid of 100-200 ml. of absolute ethanol used in several portions. The last portions of ethanol are used as wash liquid for the crystals. The crystals are finally pressed dry and washed with 25 ml. of ether. The air-dried product weighs 53-55 g. (72-74%) and melts above 275. Analysis for chlorine indicates that the salt is anhydrous. Concentration of the filtrate to a volume of about 25 ml. yields an additional 1-2 g. total yield 73-77%. The entire synthesis may be completed in one day. 

If the urethane is to be hydrolyzed immediately, there is no need to isolate it. Instead, after distillation of most of the ether and alcohol from the flask in which the urethane is formed, 700 ml. of concentrated hydrochloric acid is added, and the mixture is heated under reflux for 4 hours. The solution is then distilled from a steam bath under aspirator vacuum (Note 11), and the putrescine dihydrochloride is isolated as described above. The total yield is 55-57 g. (74-77%). 

Solid putrescine dihydrochloride should not be heated unduly long at 100°, as it may turn pink. 

Putrescine dihydrochloride has been prepared by the Hofmann degradation of adipamide 3.. s by the Curtius degradation of adipyl hydrazide through the urethane by the Curtius degradation of adipyl azide obtained from adipyl chloride and sodium azide by the Schmidt degradation of adipic acid with hydrogen azide by the reduction of succinonitrile, succinaldoxime, or 7-phthalimidobutyronitrile with sodium and from N-ben-zoyl-7-iodobutylamine ... 

Putrescine dihydrochloride has been prepared by the Hofmann degradation of adipamide by the Curtius degradation of... 

I uranc. I he mixluie sepaialcs into two layers the upper I HI layer is washed with sodium chloride solution, dried further, filtered, and the product is precipitated with petroleum ether. Use of an ester for hydrazide formation is illustrated by a synthesis of putrescine dihydrochloride. " ... 

Hydrazide— azide. In the synthesis of putrescine dihydrochloride, diethyl adipate is converted into the dihydrazide, which on reaction with nitrous acid affords... 

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