n-Butyl borate (CAS NO.: ), which is also known as Butyl borate, could be produced through the following synthetic routes.

In a 2-l. round-bottomed flask, equipped with a 200-cc. dropping funnel and a 30-cm. column filled with glass beads, and connected to a 40–50 cm. condenser, are placed 124 g. (2 moles) of boric acid, 666 g. (9 moles) of technical n-butyl alcohol, and a few chips of porous plate. The reaction mixture is heated to gentle boiling, and the rate of heating is adjusted so that 90–100 cc. of distillate is collected per hour. The temperature of the vapor at the top of the column remains constant at 91° over a period of three to three and one-half hours while the azeotropic mixture of n-butyl alcohol and water distils. After two hours, the upper layer of n-butyl alcohol in the distillate is separated from the water, dried with a little anhydrous potassium carbonate or magnesium sulfate, and returned to the reaction mixture through the separatory funnel. Likewise, after the third hour of heating, the n-butyl alcohol in the distillate is separated, dried, and returned to the reaction flask.

During the third hour of heating, the temperature at the top of the column rises slowly as the removal of the water approaches completion. After the fourth hour, when the temperature of the distilling vapor has attained 110–112°, the heating is discontinued, and the reaction mixture is transferred to a 2-l. Claisen flask with the least possible exposure to atmospheric moisture. The unreacted n-butyl alcohol is removed by distillation under reduced pressure until the thermometer registers a sudden rise in temperature. The receiver is then changed, and the main fraction of n-butyl borate distils almost entirely at 103–105°/8 mm. or 114–115°/15 mm. A negligible residue remains in the distilling flask. The weight of the distilled n-butyl borate, which contains a small amount of n-butyl alcohol, is 410–435 g. (89–94 per cent of the theoretical amount). From the aqueous distillate and the fore-run of the vacuum distillation, 190–210 g. of n-butyl alcohol is recovered.

The main fraction of n-butyl borate is redistilled from a Claisen flask provided with an indented fractionating column, and the first 4–6 cc. of distillate is rejected. The purified product, b.p. 103–105°/8 mm. or 114–115°/15 mm., weighs 400–425 g. (87–92 per cent of the theoretical amount).