1.4- butynediol

Butynediol (2-butyne-l,4-diol melting point 58°C, boiling point 248°C, density 1.114, flash point 152°C) is a stable crystalline solid but violent reactions can take place in the presence of certain contaminants, particularly 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 te(inagnesium bromide) with paraformaldehyde. 

All manufacturers of butynediol use this formaldehyde ethynylation process, and yields of butynediol may be in excess of 90 percent, in addition to 4 to 5% propargyl alcohol. 

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 herbicide, Carbyne (Barban), 4-chloro-2-butynyl-A-(3-chlorophenyl)carba-mate (CnH9Cl2N02). 

Butynediol undergoes the usual reactions of primary alcohols that contribute to its use as a chemical intermediate. Because of its rigid, linear structure, many reactions forming cyclic products from butanediol or m-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. 

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HOCH2CH = CHCH2OH. Colourless stable liquid used in the manufacture of insecticides, resins and pharmaceuticals. Both cis- and rruwi-isomers are known. Prepared by hydrogenation of butynediol over a catalyst. 

Butynediol. Butynediol, 2-butyne-l,4-diol, [110-65-6] was first synthesized in 1906 by reaction of acetylene bis(magnesium bromide) with paraformaldehyde (43). It is available commercially as a crystalline soHd or a 35% aqueous solution manufactured by ethynylation of formaldehyde. Physical properties are Hsted in Table 2. 

Table 2. Physical Properties of Butynediol, Butenediol, and Butanediol...

Rea.ctlons, Butynediol undergoes the usual reactions of primary alcohols. Because of its rigid, linear stmcture, many reactions forming cycHc products from butanediol or i j -butenediol give only polymers with butynediol. 

The hydroxyl groups can be alkylated with the usual alkylating agents. To obtain aryl ethers a reverse treatment is used, such as treatment of butynediol toluenesulfonate or dibromobutyne with a phenol (44). Alkylene oxides give ether alcohols (46). 

In the presence of acid catalysts, butynediol and aldehydes (47) or acetals (48) give polymeric acetals, useful intermediates for acetylenic polyurethanes suitable for high energy soHd propellants. 

Butynediol can be hydrogenated partway to butenediol or completely to butanediol. 

When aqueous solutions of sodium bisulfite are heated with butynediol, one or two moles add to the triple bond, forming sodium salts of sulfonic acids (61). 

In the presence of mercuric salts, butynediol rapidly isomerizes to 1-hydroxy-3-buten-2-one (62). 

Butynediol is more difficult to polymerize than propargyl alcohol, but it cyclotrimerizes to hexamethylolbenzene [2715-91 -5] (benzenehexamethanol) with a nickel carbonyl—phosphine catalyst (64) with a rhodium chloride—arsine catalyst a yield of 70% is claimed (65). 

When heated with acidic oxide catalysts, mixtures of butynediol with ammonia or amines give pyrroles (66) (see Pyrrole AND PYRROLE DERIVATIVES). 

Ma.nufa.cture. AU. manufacturers of butynediol use formaldehyde ethynylation processes. The earliest entrant was BASF, which, as successor to I. G. Farben, continued operations at Ludwigshafen, FRG, after World War II. Later BASF also set up a U.S. plant at Geismar, La. The first company to manufacture in the United States was GAF in 1956 at Calvert City, Ky., and later at Texas City, Tex., and Seadrift, Tex. The most recent U.S. manufacturer is Du Pont, which went on stream at La Porte, Tex., about 1969. Joint ventures of GAF and Hbls in Mad, Germany, and of Du Pont and Idemitsu in Chiba, Japan, are the newest producers. 

At the end of Wodd War II the butynediol plant and process at Ludwigshafen were studied extensively (67,68). Vadations of the original high pressure, fixed-bed process, which is described below, are stiU in use. However, ak of the recent plants use low pressures and suspended catalysts (69—75). 

The reactors were thick-waked stainless steel towers packed with a catalyst containing copper and bismuth oxides on a skiceous carrier. This was activated by formaldehyde and acetylene to give the copper acetyUde complex that functioned as the tme catalyst. Acetylene and an aqueous solution of formaldehyde were passed together through one or more reactors at about 90—100°C and an acetylene partial pressure of about 500—600 kPa (5—6 atm) with recycling as required. Yields of butynediol were over 90%, in addition to 4—5% propargyl alcohol. 

Shipment, Storage, and Price. Butynediol, 35% solution, is available in tank cars, tank trailers, and dmms. Stainless steel, nickel, aluminum, glass, and various plastic and epoxy or phenoHc liners have ak been found satisfactory. Rubber hose is suitable for transferring. The solution is nonflammable and freezes at about —5°C. 

Butynediol soHd flakes are packed in polyethylene bags inside dmms. The product is hygroscopic and must be protected from moisture. 

Specifications and Analytical Methods. The commercial aqueous solution is specified as 34% minimum butynediol, as determined by bromination or refractive index. Propargyl alcohol is limited to 0.2% and formaldehyde to 0.7%. 

The commercial flake is specified as 96.0% minimum butynediol content, with a maximum of 2.0% moisture. Purity is calculated from the freezing point (at least 52°C). 

Butynediol is a primary skin irritant and sensitizer, requiring appropriate precautions. Acute oral toxicity is relatively high LD q is 0.06 g/kg for white... 

Uses. Most butynediol produced is consumed by the manufacturers in manufacture of butanediol and butenediol. Smak amounts are converted to ethers with ethylene oxide. 

Ma.nufa.cture. Butenediol is manufactured by partial hydrogenation of butynediol. Although suitable conditions can lead to either cis or trans isomers (111), the commercial product contains almost exclusively iVj -2-butene-l,4-diol Trans isomer, available at one time by hydrolysis of l,4-dichloro-2-butene, is unsuitable for the major uses of butenediol involving Diels-Alder reactions. The Hquid-phase heat of hydrogenation of butynediol to butenediol is 156 kj/mol (37.28 kcal/mol) (112). 

The original German process used either carbonyl iron or electrolytic iron as hydrogenation catalyst (113). The fixed-bed reactor was maintained at 50—100°C and 20.26 MPa (200 atm) of hydrogen pressure, giving a product containing substantial amounts of both butynediol and butanediol. Newer, more selective processes use more active catalysts at lower pressures. In particular, supported palladium, alone (49) or with promoters (114,115), has been found useful. 

Principal impurities are butynediol (specified as 2.0% maximum, typically less than 1%), butanediol, and the 4-hydroxybutyraldehyde acetal of butenediol. Moisture is specified at 0.75% maximum (Kad-Fischer titration). Typical technical grade butenediol free2es at about 8°C. 

Health nd Safety Factors. Butenediol is noncorrosive and stable under normal handling conditions. It is a primary skin irritant but not a sensitizer contact with skin and eyes should be avoided. It is much less toxic than butynediol. The LD q is 1.25 mL/kg for white rats and 1.25—1.5 mL/kg for guinea pigs. 

Butanediol. 1,4-Butanediol [110-63-4] tetramethylene glycol, 1,4-butylene glycol, was first prepared in 1890 by acid hydrolysis of N,]S3-dinitro-l,4-butanediamine (117). Other early preparations were by reduction of succinaldehyde (118) or succinic esters (119) and by saponification of the diacetate prepared from 1,4-dihalobutanes (120). Catalytic hydrogenation of butynediol, now the principal commercial route, was first described in 1910 (121). Other processes used for commercial manufacture are described in the section on Manufacture. Physical properties of butanediol are Hsted in Table 2. 

Ma.nufa.cture. Most butanediol is manufactured in Reppe plants via hydrogenation of butynediol. Recendy an alternative route involving acetoxyiation of butadiene has come on stream and, more recendy, a route based upon hydroformylation of allyl alcohol. Woddwide butanediol capacity has climbed steadily for many years. In 1990 it was estimated to be 428,000 metric tons (141), as compared to a Htde more than 70,000 metric tons in 1975... 

Acetylene is condensed with carbonyl compounds to give a wide variety of products, some of which are the substrates for the preparation of families of derivatives. The most commercially significant reaction is the condensation of acetylene with formaldehyde. The reaction does not proceed well with base catalysis which works well with other carbonyl compounds and it was discovered by Reppe (33) that acetylene under pressure (304 kPa (3 atm), or above) reacts smoothly with formaldehyde at 100°C in the presence of a copper acetyUde complex catalyst. The reaction can be controlled to give either propargyl alcohol or butynediol (see Acetylene-DERIVED chemicals). 2-Butyne-l,4-diol, its hydroxyethyl ethers, and propargyl alcohol are used as corrosion inhibitors. 2,3-Dibromo-2-butene-l,4-diol is used as a flame retardant in polyurethane and other polymer systems (see Bromine compounds Elame retardants). 

Much more important is the hydrogenation product of butynediol, 1,4-butanediol [110-63-4]. The intermediate 2-butene-l,4-diol is also commercially available but has found few uses. 1,4-Butanediol, however, is used widely in polyurethanes and is of increasing interest for the preparation of thermoplastic polyesters, especially the terephthalate. Butanediol is also used as the starting material for a further series of chemicals including tetrahydrofuran, y-butyrolactone, 2-pyrrohdinone, A/-methylpyrrohdinone, and A/-vinylpyrrohdinone (see Acetylene-DERIVED chemicals). The 1,4-butanediol market essentially represents the only growing demand for acetylene as a feedstock. This demand is reported (34) as growing from 54,000 metric tons of acetylene in 1989 to a projected level of 88,000 metric tons in 1994. 

Substances that have been hydrogenated in slurry reactors include nitrobenzene with Pd-C, butynediol with Pd-CaCO,3, chlorobenzene with Pt-C, toluene with Raney Ni, and acetone with Raney Ni. 

Fire Hazards - Flash Point (deg. F) 263 OC (pure butynediol) Flammable Limits in Air (%) Not pertinent Fire Extinguishing Agents Water, alcohol foam, dry chemical or carbon dioxide Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards of Combustion Products Not pertinent Behavior in Fire Not pertinent Ignition Temperature (deg. F) No data Electrical Hazard Not pertinent Burning Rate No data. 

Butadiene could also be obtained by the reaction of acetylene and formaldehyde in the vapor phase over a copper acetylide catalyst. The produced 1,4-butynediol is hydrogenated to 1,4-butanediol. Dehydration of 1,4-butanediol yields butadiene. 

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