SYNTHESIS OF ETHYL BUT-3-ENOATE (Ethyl vinylacetate)

• Prepare vinylacetyl chloride from 50g (31 ml, 0.42 mol) of thionyl chloride and 30g (0.35 mol) of vinylacetic acid following the procedure described for butyryl chloride; 27 g (0.26 mol) of the acid chloride, b.p. 98-99 °C, are obtained. 

• Place 12.6g (16.0ml, 0.27 mol) of absolute ethanol is a 250-ml two-necked flask provided with a reflux condenser and dropping funnel. 

• Cool the flask in ice and introduce the vinylacetyl chloride into the dropping funnel; insert a calcium chloride guard-tube into the mouth of the funnel. 

• Add the acid chloride dropwise (45 minutes) to the alcohol with frequent shaking. 

• Remove the ice and allow to stand for 1 hour. 

• Pour the reaction mixture into water, wash with a little sodium hydrogen carbonate solution, then with water, and dry with anhydrous calcium sulphate. 

• Distil from a 50-ml flask through a short fractionating column, and collect the ethyl vinylacetate at 125-127 °C. The yield is 22 g (75%).

Cognate preparation: Phenyl cinnamate

• Place 72g (0.48 mol) of cinnamic acid and 60g (37 mol, 0.5 mol) of thionyl chloride in a 250-ml flask, fitted with a reflux condenser which is connected to a gas absorption trap. 

• Heat the mixture on a water bath, cautiously at first, until hydrogen chloride ceases to be evolved (about 1 hour), allow to cool and add 47g (0.5 mol) of pure phenol. 

• Heat the mixture on a water bath until no further evolution of hydrogen chloride is observed (about 1 hour). 

• Then place the apparatus on a ceramic-centred wire gauze and heat the flask until the contents are brought just to the reflux temperature in order to complete the reaction: do not heat unduly long as prolonged heating leads to loss of product due to decomposition and polymerisation. 

• Allow the reaction mixture to cool and distil under diminished pressure; collect the fraction of b.p. 190-210 °C/15 mmHg. 

• This solidifies to a pale yellow solid, m.p. 66-69 °C, weighing 98 g. 

• Grind it to a powder in a glass mortar and wash the powder with 250 ml of cold 2 per cent sodium hydrogen carbonate solution. 

• Recrystallise from rectified spirit (150 ml); 81g (72%) of pure phenyl cinnamate (white crystals) of m.p. 75-76 °C are obtained.

Phenyl propanoate:

• Slowly add 196g (120 ml) of redistilled thionyl chloride to a mixture of 150g (1.6mol) of pure phenol and 132g (133ml, 1.7mol) of propanoic acid (with the addition of a gas absorption device), warming to drive off all the sulphur dioxide and hydrogen chloride, and distilling; 190g (79%) of phenyl propanoate, b.p. 202-212°C (the pure substance boils at 21 1 °C), are obtained.