2-Ethyl-2-oxazoline oxazolines towards ring-opening by chloride ions during protonation of the imine nitrogen. The direct reaction of propanoyl chloride with 2-chloroethylamine hydrochloride in the presence of triethylamine avoids the formation of water. Propanal reacts with 2-aminoethanol in "t"-butanol to 2-ethyl-2-oxazoline in the presence of the iodinating reagent 1,3-diiodo-5,5-dimethylhydantoin (DIH) and potassium carbonate. 2-Ethyl-2-oxazoline is a readily water-soluble, colorless liquid which is also soluble in a variety of organic solvents and possesses an amine-like smell. Aqueous solutions react alkaline. The compound is stable in alkaline but hydrolyses under acid action. In anhydrous form, 2-ethyl-2-oxazoline is mostly used as a monomer. The cationic
Ethyl cyanohydroxyiminoacetate product can even be obtained in virtually quantitative yield. The compound can be purified by recrystallization from ethanol or ethyl acetate. Compared with the benzotriazole derivatives 1-hydroxybenzotriazole (HOBt) and 1-hydroxy-7-azabenzotriazole (HOAt) (which are widely used as peptide-linking reagents but are explosive), ethyl cyanohydroxyiminoacetate exhibits a markedly slowed thermal decomposition on heating. Ethyl cyanohydroxyiminoacetate is a white solid which is soluble in many solvents common in the synthesis of peptides, such as dichloromethane or dimethylformamide (DMF). In crystalline form, the compound is present as an oxime, whereas it exists as a salt or in a strongly basic solution predominantly as a