Distillation, flash theory

A mixture of 5 mmol each of 80% NaH and 15-crown-5 in 50 ml of absol. toluene is stirred at 20°C under inert gas for 10 min and a solution of 5 mmol of 2-diethoxy-phosphoryl)-butiric acid 3-[(l-methyl-lH-imidazol-5-yl)methyl]-2-oxo-propyl ester in 50 ml of absol. toluene is then added dropwise. Stirring is continued for a further 15 min under inert gas and the mixture is hydrolyzed with a little water until phase separation is detectable. After separating off the organic phase, the aqueous layer is saturated with NaCI and extracted several times with CHCI3. The combined organic phases are the solvent is distilled off at 40°C in vacuo and the residue 3-ethyl-4-[(l-methyl-lH-imidazol-5-yl)methyl]-5H-furan-2-one is purified twice by flash chromatography (silica gel ethyl acetate/CH3OH). Yield 52% of theory virtually colorless oil. 

Ethylene (Ethene or Elayl), H2C CH2 mw 28.05 colorless, flammable, dangerous to handle gas with characteristic sweet odor and taste sp gr 0.975 (air = 1.0), mp —169.4°, bp —103.8°, flash p —136°C explosive limits in air, % by vol, lower 3.0 upper 34.0 si sol in w, more in ale sol in eth. Ethylene is a major component of petroleum refinery gas from cracking units, and is sometimes recovered therefrom by distillation or other means. Some pure ethylene is produced by passing hot ethanol vapors over a catalyst, such as activated alumina (Ref 4). Its laboratory prepn consists of heating ethanol in definite proportions with sulfuric acid of certain concns. By using a 90% acid and 90% ale, ethylene can be produced in a regular stream at a yield of 84 to 85% of theory (Ref 2). 

Surprisingly, we found that the reaction of an alcohol with 1-chloroethyl-N,N-dialkylcarbamates can proceed through B mechanism to give alkylation rather than acylation (Ref. 195). This result appears to be a violation of the HSAB theory. In a typical example, N-(1-chloroethyloxy-carbonyl) piperidine was added to a stirred mixture of sodium hydrocarbonate and methanol at 25°C. The reaction was instantaneous. Solids were removed by filtration, excess alcohol was then distilled off and the resulting product was isolated by flash chromatography in 96% yield [Scheme 139]. 

---