Page 172 - Chemical and process design handbook

Speight_Part II_B 11/7/01 3:11 PM Page 2.113

BUTYNEDIOL

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Butynediol (2-butyne-1,4-diol; melting point: 58 C, boiling point: 248 C,
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density: 1.114, flash point: 152 C) is a stable crystalline solid but violent
reactions can take place in the presence of certain contaminants, particu-
larly at elevated temperatures. In the presence of certain heavy-metal salts,
such as mercuric chloride, dry butynediol can decompose violently.
Heating with strongly alkaline materials should be avoided.
Butynediol was first synthesized in 1906 by reaction of acetylene
bis(magnesium bromide) with paraformaldehyde.
HC≡CH + 2HCH=O → HOCH C≡CCH OH
2 2
All manufacturers of butynediol use this formaldehyde ethynylation
process, and yields of butynediol may be in excess of 90 percent, in addi-
tion to 4 to 5% propargyl alcohol.
HC≡CH + HCH=O → HC≡CH OH
2
Most butynediol produced is consumed in the manufacture of butane-
diol and butenediol. Butynediol is also used for conversion to ethers with
ethylene oxide and in the manufacture of brominated derivatives that are
useful as flame retardants. Butynediol was formerly used in a wild oat her-
bicide, Carbyne (Barban), 4-chloro-2-butynyl-N-(3-chlorophenyl)carba-
mate (C H Cl NO ).
11 9 2 2
Butynediol undergoes the usual reactions of primary alcohols that
contribute to its use as a chemical intermediate. Because of its rigid, lin-
ear structure, many reactions forming cyclic products from butanediol or
cis-butenediol give only polymers with butynediol. Both hydroxyl groups
can be esterified normally, and the monoesters are readily prepared as
mixtures with diesters and unesterified butynediol, but care must be taken
in separating them because the monoesters disproportionate easily.
The hydroxyl groups can be alkylated with the alkylating agents,
although a reverse treatment is used to obtain aryl ethers; for example,
treatment of butynediol toluene sulfonate or dibromobutyne with a phenol

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