Amyl alcohols Production

Amylene is a general name for the ethylenic hydrocarbons of the molecular formula CjHio. Two of these hydrocarbons are the main products of the dehydration of the appropriate amyl alcohols ... 

This secondary amyl alcohol (2-pentanol) is a commercial product (Sharpies Solvent Corporation, etc.). 

Di-n-amyl ether. Use 50 g. (61 5 ml.) of n-amyl alcohol (b.p. 136-137°) and 7 g. (4 ml.) of concentrated sulphuric acid. The calculated volume of water (5 ml.) is collected when the temperature inside the flask rises to 157° (after 90 minutes). Steam distil the reaction mixture, separate the upper layer of the distillate and dry it with anhydrous potassium carbonate. Distil from a 50 ml. Claisen flask and collect the fractions of boiling point (i) 145-175° (13 g.), (ii) 175-185° (8 g.) and (iii) 185-190° (largely 185-185-5°) (13 g.). Combine fractions (i) and (u), reflux for 1 hour in a small flask with 3 g. of sodium, and distil from the sodium amyloxide and excess of sodium this yields 9 5 g. of fairly pure n-amyl ether (iv). The total yield is therefore 22 - 5 g. A perfectly pure product, b.p. 184 185°, is obtained by further distillation from a Little sodium. 

Mixtures of isomeric amyl alcohols (1-pentanol and 2-methyl-1-butanol) are often preferred because the different degree of branching imparts a more desirable combination of properties they are also less expensive to produce commercially. One such mixture is a commercial product sold under the name Primary Amyl Alcohol by Union Carbide Chemicals and Plastics Company Inc. 

Dehydration. Dehydration of amyl alcohols is important for the preparation of specialty olefins and where it may produce unwanted by-products under acidic reaction conditions. Olefin formation is especially facile with secondary or tertiary amyl alcohols under acidic conditions. The reverse reaction, hydration of olefins, is commonly used for the preparation of alcohols. 

An example of a specialty olefin from an amyl alcohol is Phillips Petroleum s new process for 3-methyl-1-butene (used in the synthesis of pyrethroids) from the catalytic dehydration of 3-methyl-1-butanol (21,22). The process affords 94% product selectivity and 94% alcohol conversion at 310°C and 276 kPa (40 psig). 

Eriedel-Crafts alkylation of ben2ene with isomeric amyl alcohols proceeds with some rearrangement. Eor example, both 2- and 3-pentanol gave the identical product mixture (60% 2-phenylpentane, 31% 3-phenylpentane, and 9% / f/-pentylben2ene) from reaction with ben2ene in the presence of BE catalyst (85). 

Other Reactions. Primary amyl alcohols can be halogenated to the corresponding chlorides by reaction with hydrogen chloride in hexamethylphosphoramide (87). Neopentyl chloride [753-89-9] is formed without contamination by rearrangement products. A convenient method for preparing / f/-amyl bromide and iodide involves reaction of / f/-amyl alcohol with hydrobromic or hydroiodic acid in the presence of Li or Ca haUde (88). The metal haUdes increase the yields (85 —95%) and product purity. 

Three significant, commercial processes for the production of amyl alcohols include separation from fusel oils, chlorination of C-5 alkanes with subsequent hydrolysis to produce a mixture of seven of the eight isomers (Pennsalt) (91), and a low pressure 0x0 process, or hydroformylation, of C-4 olefins followed by hydrogenation of the resultant C-5 aldehydes. 

Fusel Oils. The original source of amyl alcohols was from fusel oil which is a by-product of the ethyl alcohol fermentation industry. Refined amyl alcohol from this source, after chemical treatment and distillation, contains about 85% 3-methyl-1-butanol and about 15% 2-methyl-1-butanol, both primary amyl alcohols. Only minor quantities of amyl alcohol are suppHed from this source today. A German patent discloses a distillative separation process for recovering 3-methyl-1-butanol from fusel oil (93). 

Prior to 1975, reaction of mixed butenes with syn gas required high temperatures (160—180°C) and high pressures 20—40 MPa (3000—6000 psi), in the presence of a cobalt catalyst system, to produce / -valeraldehyde and 2-methylbutyraldehyde. Even after commercialization of the low pressure 0x0 process in 1975, a practical process was not available for amyl alcohols because of low hydroformylation rates of internal bonds of isomeric butenes (91,94). More recent developments in catalysts have made low pressure 0x0 process technology commercially viable for production of low cost / -valeraldehyde, 2-methylbutyraldehyde, and isovaleraldehyde, and the corresponding alcohols in pure form. The producers are Union Carbide Chemicals and Plastic Company Inc., BASF, Hoechst AG, and BP Chemicals. 

Union Carbide Chemicals and Plastics Company Inc. is the only producer of C-5 oxo derived alcohols (148,150) in the United States. About 75% of the 30,000 t of valeraldehyde and 2-methylbutyraldehyde produced by the oxo process was converted to the isomeric mixture of primary amyl alcohols in 1988 (150). The primary amyl alcohol mixture was available in tank car quantities for 1.02/kg in 1991. The Dow Chemical Company appears to have stopped commercial production of / fZ-amyl alcohol (151). 

Table 8 summarizes domestic consumption by use for amyl alcohols. About 55% of the total 1-pentanol and 2-methyl-1-butanol production is used for zinc diamyldithiophosphate lubrication oil additives (150) as important corrosion inhibitors and antiwear additives. Amyl xanthate salts are useful as frothers in the flotation of metal ores because of their low water solubiUty and miscibility with phenoHcs and natural oils. Potassium amyl xanthate, a collector in flotation of copper, lead, and zinc ores, is no longer produced in the United States, but imports from Germany and Yugoslavia were 910 —1100 t in 1989 (150). 

Another significant appHcation for amyl alcohols is for production of amyl acetates. Production of amyl acetates in 1987 is estimated to have been 4.5-5.5 X 10 t about 50% of the domestic demand is for lacquers (150). Union Carbide Chemicals and Plastics Company Inc. is the only U.S. producer. 

The principal component of primary amyl alcohol, 1-pentanol, although itself a good solvent, is useful for the preparation of specific chemicals such as pharmaceuticals and other synthetics (153,154). Production of primary amyl acetate and its esters for solvent appHcations has seen low growth since the 1970s because of the decline of nitroceUulose lacquers and the introduction of new solvent systems. 

Growth appHcations for amyl alcohols appear to be shifting toward higher boiling esters as plasticizers, perfumes, fragrances, and production of fine chemicals. 

There is some beneficiation of talc by froth flotation (qv), practiced especially on ultramafic-type deposits. In this process (Fig. 2), talc is milled to its hberation size (—100 mesh (ca 0.15 mm)) using ball mills or ring-type roUer mills and then slurried at 10—30% in water. Flotation is done in conventional multistage float cells using methyl amyl alcohol as a frother. Typically two to four stages are required to upgrade the ore from 50—70% talc to 90—98%. The product is filtered and then flash-dried and milled to a final product. 

Primary Amyl Alcohols. Primary amyl alcohols (qv) are manufactured by hydroformylation of mixed butenes, followed by dehydrogenation (114). Both 1-butene and 2-butene yield the same product though in slightly different ratios depending on the catalyst and conditions. Some catalyst and conditions produce the alcohols in a single step. By modifying the catalyst, typically a cobalt carbonyl, with phosphoms derivatives, such as tri( -butyl)phosphine, the linear alcohol can be the principal product from 1-butene. 

In the production of KNO3 from KCl and HNO3, the product HCl is removed continuously from the aqueous phase by contact with amyl alcohol, thus forcing the reaction to completion (Daniel and Bhimberg, Chim. Jnd., 4, 27 [1957]). 

The designation Ac signifies acyl-oxygen fission, whereas A1 is alkyl-oxygen fission. When n-amyl alcohol was hydrolyzed in 0-enriched water, the 0 appeared in the product acid rather than the alcohol, showing that alkyl-oxygen fission could not have occurred. Carpenter gives many examples of isotopic studies. 

The reaction conditions were optimized to afford clean coupling of enol tosylate 32 using only a slight excess of amide 24 (1.05equiv) at 100 °C, 5mol% Pd2(dba)3/ dppb catalyst, and a toluene/tert-amyl alcohol solvent system. Even under the harsh reaction conditions required for complete conversion of the tosylate (100 °C, 20 h) no detectable E/Z isomerization was seen, providing further proof that the hindered nature of the enamide aids stability to isomerization. Treatment of the mixture with activated carbon (Darco KB-B) at the end of the reaction followed by isolation of the product by crystallization, afforded enamide 22 in 92% isolated yield. 

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