1. It is essential to use pure reagents. Commercial
ethyl isobutyrate may be purified satisfactorily by washing with
10 per cent sodium carbonate solution, drying over
Drierite for several days, and fractionating through an
effective column; material boiling over a one-degree range (110–111°) is recommended for this preparation.
Benzoyl chloride was purified by distillation under reduced pressure, and a fraction collected over less than a two-degree range was used.
The
bottle containing an
ether solution of
0.85 mole of triphenylmethylsodium is immersed to two-thirds of its depth in an ice bath. When the bottle is thoroughly cold, the stopper is removed while a tube delivering a rapid stream of dry
nitrogen is held at the mouth of the bottle. The bottle is quickly fitted with a
three-holed rubber stopper carrying a
mechanical stirrer (with open shaft), a
dropping funnel, and a bent tube which extends into the bottle for a distance of 1 cm. below the neck. A slow stream of dry
nitrogen passes through the bent tube; the
nitrogen supply is also connected to the top of the dropping funnel.
One hundred two grams (0.875 mole) of ethyl isobutyrate is added rapidly to the vigorously stirred contents of the bottle. After five minutes,
123 g. (101 cc., 0.875 mole) of benzoyl chloride is added through the dropping funnel at such a rate that the mixture does not reflux too vigorously (the addition takes about five minutes). Stirring is continued for two or three minutes after the addition is complete. The bottle is then removed from the ice bath, stoppered, shaken, and allowed to stand for half an hour. The reaction mixture is transferred to a
2.5-l. separatory funnel and the
mercury drained off. The remaining mixture is extracted with 300 cc. of water, any sludge formed being collected separately. The sludge is extracted with a little
ether, the extract being added to the
ether layer in the funnel. The
ether solution is washed with two
100-cc. portions of 10 per cent sodium carbonate solution, and dried by shaking with
50 g. of anhydrous sodium or magnesium sulfate and by standing with
50 g. of Drierite in a
stoppered 2-l. Erlenmeyer flask. The solution is filtered into a
2-l. round-bottomed flask and the
ether removed by distillation. The residue is transferred to a
1-l. Claisen flask and distilled in vacuum, using a
metal or oil bath and collecting all the material boiling below 175° at 15 mm. The distillate is transferred to a
200-cc. round-bottomed flask fitted with a 6-inch Widmer fractionating column and redistilled from a metal bath. The
ethyl benzoyldimethylacetate boils at
146–148°/15 mm. and weighs
115–125 g. (
61–67 per cent of the theoretical amount based on the quantity of
triphenylmethylsodium used). (Charles R. Hauser and Boyd E. Hudson, Jr., private communication.)