Phenylpropargyl aldehyde diethyl acetal

PHENYLPROPARGYL ALDEHYDE DIETHYL ACETAL (Propiolaldehyde, phenyl-, diethyl acetal) 

Into a 300-ml. three-necked flask equipped with a nitrogen inlet, a thermometer, and a short fractionating column (Note 1) are charged 74.1 g. (0.50 mole) of triethyl orthoformate, 51.0 g. (0.50 mole) of phenylacetylene (Note 2), and 3.0 g. of zinc iodide (Note 3). Ethanol is slowly distilled from the reaction mixture, which must be heated to about 135° before refluxing in the still-head begins. A total of 29-35 ml. of distillate, b.p. 65-88° (mostly 78°), is collected over a period of about 1 hour as the temperature of the reaction mixture gradually rises to 200° to 210° (Note 4). The reaction mixture is cooled to room temperature and filtered with suction. The flask and the small amount of precipitate on the filter paper are washed with 5 ml. of ether. The filtrate and ether wnshings are combined and distilled. After 

The checkers found a 12-inch Vigreux column satisfactory. 

The checkers purchased pure phenylacetylene from Gesell-schaft fur TeerverwertungmbH., Duisburg-Meiderich, Germany. 

The submitters report that zinc nitrate appears to be equivalent to zinc iodide as a catalyst and that zinc chloride (commercial anhydrous grade) is satisfactory but requires 2-3 hours of heating and gives 64-70% yield. 

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