In a 1-l. three-necked flask, fitted with a mechanical stirrer, condenser, and 500-cc. separatory funnel, is placed 13.4 g. (0.55 atom) of magnesium shavings (Note 1). The shavings are then covered with 50 cc. of anhydrous ether. A crystal or two of iodine and 3 g. of sec.-butyl chloride (Note 2) are added. The reaction is started by warming the flask with a microburner and is then allowed to proceed by its own heat for twenty minutes. A second addition of 50 cc. of anhydrous ether is made. A solution of 43 g. (the remainder of 0.5 mole) of sec.-butyl chloride in 300 cc. anhydrous ether is added over a period of twenty minutes. Vigorous refluxing is avoided by externally cooling the flask with water. The heat from the reaction causes refluxing to continue for twenty minutes after the addition of the halide solution. The reaction mixture is then gently refluxed for one hour with a microburner. The reaction flask is surrounded by an ice and salt mixture and the solution cooled to − 12° in an atmosphere of nitrogen (Note 3). The nitrogen gas, obtained directly from a cylinder, is dried by passing through two wash bottles containing concentrated sulfuric acid and a phosphorus pentoxide tower. It is admitted to the flask through an entry tube 10 mm. in diameter at a height of about 60 mm. above the surface of the ether solution. An additional 100 cc. of ether is added, and the separatory funnel is replaced by a thermometer.

The cylinder of nitrogen is then replaced by a cylinder of carbon dioxide. The gas after passing through the drying train enters the reaction flask through the entry tube (Note 4). The rate of flow is regulated so that the temperature of the reaction mixture does not rise above − 5° when rapid stirring is in progress. After one and one-half hours (Note 5) the temperature drops to − 12° and does not rise on increasing the rate of flow of carbon dioxide. The drop in temperature is taken as an end-point for the carbonation.

The reaction mixture is then hydrolyzed in the flask with about 500 cc. of 25 per cent sulfuric acid (Note 6). Cooling the solution with ice and water permits of rapid hydrolysis without danger of loss of material through too vigorous refluxing. The mixture is transferred to a 1-l. separatory funnel and the ether layer separated. The water layer is extracted with three 50-cc. portions of ether. The combined ether extracts are washed with about 150 cc. of 25 per cent sodium hydroxide solution until all the organic acid is converted to the salt and thus removed (Note 7) and (Note 8).

The alkaline extract is boiled in a distillation apparatus, to remove ether and other volatile impurities, until its volume is decreased by 10 per cent. It is then acidified with concentrated hydrochloric acid and the acid layer separated. The water layer is then distilled from a 1-l. flask until no more oily acid comes over (Note 9). The distillate is saturated with salt and the acid layer separated. This water layer, together with the low-boiling fraction from the acid distillation, is distilled, and the distillate salted out as before.

The combined acid layers are distilled from a 75-cc. flask connected to an air condenser. The product is collected at 173–174°. The yield of acid is 39–44 g. (76–86 per cent of the theoretical amount based on the quantity of sec.-butyl chloride used) (Note 10).