BUTANEDIOL

1,4-butanediol (tetramethylene glycol, 1,4-butylene glycol; melting point: 20.2 C, boiling point: 228 C, density: 1.017, flash point: 121 C) was first prepared in 1890 by acid hydrolysis of N, N ?-dinitro-1,4-butanediamine. Other early preparations were by reduction of succinaldehyde or succinic esters and by saponification of the diacetate prepared from 1,4-dihalobutanes. Catalytic hydrogenation of butynediol, now the principal commercial route, was first described in 1910.

Butanediol is manufactured by way of hydrogenation of butynediol (the Reppe process):

An alternative route involving acetoxylation of butadiene and has come on stream, and, more recently, a route based upon hydroformylation of allyl aIcohol has also been used. Another process, involving chlorination of butadiene, hydrolysis of the dichlorobutene, and hydrogenation of the resulting butenediol, has been practiced.

A more modern process involves the use of maleic anhydride as the starting material. In the process (Fig. 1), maleic anhydride is first esterified with methanol and the ester is fed to a low-pressure vapor-phase hydrogenation system where it is converted to butanediol.

Figure 1: Manufacture of 1,4-butanediol from maleic anhydride.

Butanediol is specified as 99.5% minimum pure, determined by gas chromatography, solidifying at 19.6 C minimum. Moisture is 0.04% maximum, determined by Karl Fischer analysis (directly or by a toluene azeotrope).

Butanediol is much less toxic than its unsaturated analogs and it is neither a primary skin irritant nor a sensitizer. Because of its low vapor pressure, there is ordinarily no inhalation problem but, as with all chemicals, unnecessary exposure should be avoided.

The uses of...