In a
2-l. flask fitted with a
mechanical stirrer, a
thermometer, and a
separatory funnel, are placed a cool solution of
240 cc. (4.3 moles) of commercial sulfuric acid (sp. gr. 1.84) in 240 cc. of water, and
240 g. (296 cc., 3.24 moles) of technical n-butyl alcohol (Note
1). The whole is placed in a
large, efficient ice-salt bath.
A solution of
320 g. (1.07 moles) of crystalline sodium dichromate (350 g. of the ordinary moist technical hydrated salt is also suitable) in 200 cc. of water is dropped from the funnel into the vigorously stirred alcohol mixture as rapidly as can be done without running the temperature above 20°. When most of the
dichromate has been added, the viscosity of the reaction mixture becomes so great that the stirring is rendered inefficient. The temperature is now allowed to rise to 35° if necessary (Note
2), to accelerate the reaction.
The resulting green sirupy emulsion is diluted with an equal volume of water, whereupon 220–225 cc. of an oil containing the desired ester (Note
3), slowly separates. This oil is washed three times with water, separated, and treated with a few grams of anhydrous
sodium sulfate in order to remove most of the water. It is now distilled slowly through a
large, efficient fractionating column. The fraction boiling at
150–170° is collected, and should amount to
170–175 cc. It is washed with five
15-cc. portions of 60 per cent sulfuric acid (sp. gr. about 1.5) (Note
4), is then washed free of acids with dilute
sodium hydroxide, and finally washed free of alkali with cold water. It is rapidly dried, as before, with
sodium sulfate, and fractionated through the same distilling column. The fraction boiling at
162–166° (uncorr.) consists of
n-butyl n-butyrate, containing a small percentage of residual
butyl alcohol. The yield is
96–110 g. (
41–47 per cent of the theoretical amount).