3-Methyl-1-butanol

Description

Isoamyl alcohol has a characteristic pungent odor and repulsive taste. Industrially prepared by rectification of fusel oil.

Chemical properties

Isoamyl alcohol has a fusel oil, whiskey-characteristic, pungent odor and repulsive taste. The air odor threshold for 3-methyl-1-butanol was reported as 0.042 ppm , which provides some acute warning for exposure to this chemical.

Physical properties

Clear, colorless liquid with a pungent odor. An odor threshold concentration of 1.7 ppb_v was reported by Nagata and Takeuchi (1990).

Occurrence

Constitutes the major portion of fusel oil; also known as fermentation of amyl alcohol; it has been identified as an ester among the constituents of Roman chamomile oil; French peppermint, Java citronella, Réunion geranium, tea, Teucrium chamaedrys, Eucalyptus amigdalina, Achillea ageratum and Artemisia camphorata. It is reported present in the aromas of strawberry and raspberry. It is also reported found in over 230 natural sources including apple, apricot, banana, sweet and sour cherry, citrus peel oils and juices, berries, guava, grapes, raisin, melon, papaya, peach, pear, pineapple, asparagus, cabbage, kohlrabi, celery stalk and seed, leek, peas, potato, sauerkraut, tomato, ginger, mint oils, vinegar, mustard, bread, cheeses, butter, milk, fish，meats, cognac, rum, whiskies, cider, sherry, grape wines, tea, filberts, pecans, walnuts, oats, honey, soybean, avocado, Arctic bramble, olive, passion fruit, rose and Malay apple, mushroom, mango, tamarind, pear brandy, port, cardamom, gin, quince, radish, sukiyaki, sake, buckwheat, corn oil, sweet corn, laurel, malt, wort, cherimoya, loquat, Bourbon vanilla, shrimp, oysters, crayfish, mussels and scallops

Characteristics

Amyl alcohols (pentanols) have eight isomers. All are flammable, colorless liquids, except the isomer 2,2- dimethyl-1-propanol, which is a crystalline solid.

The Uses of 3-Methyl-1-butanol

3-Methyl-1-butanol and 2-methyl-1-butanol are normally used as apple or banana flavoring agents for wine. They can also be used as chemical intermediates and solvents in pharmaceutical products.

The Uses of 3-Methyl-1-butanol

Isoamylol is one of the several isomers of amyl alcohol and the main ingredient in the production of banana oil.

The Uses of 3-Methyl-1-butanol

3-Methyl-1-butanol is used as solvents for oils, fats, resins, and waxes; in the plastics industry in spinning polyacrylonitrile; and in manufacturing lacquers, chemicals, and pharmaceuticals. It is also used as flavoring agents and in fragrances. Industrial exposure is principally by the dermal contact and inhalation.

Definition

ChEBI: Isoamylol is an primary alcohol that is butan-1-ol in which a hydrogen at position 3 has been replaced by a methyl group. It has a role as a xenobiotic metabolite, a Saccharomyces cerevisiae metabolite and an antifungal agent. It is a primary alcohol, a volatile organic compound and an alkyl alcohol. It derives from a hydride of an isopentane.

Production Methods

Isoamyl alcohol has a characteristic pungent odor and repulsive taste. Industrially prepared by rectification of fusel oil.

Preparation

3-Methyl-1-butanol and 2-methyl-1-butanol were first isolated from fusel oils, by-products of ethanol fermentation by yeast. These compounds can also be derived from the chlorination of pentane followed by hydrolysis. Another alternative process is the oxo process, a general strategy for the manufacture of C4 and higher alcohols. Both the chlorination process and the oxo process are current commercial processes for the production of 3-methyl-1-butanol and 2-methyl-1-butanol, but the oxo process via the hydroformylation reaction is the more popular. Two main technologies are used for the process. The first was brought on stream by Ruhrchemie in Germany and Exxon in USA in the 1940s and is generally referred to as "high-pressure cobalt catalyst technology." The active catalyst species is cobalt hydrocarbonyl, and a pressure of 200–300 atm is required to maintain the stability of the catalyst. In the early 1960s, Shell commercialized a modern version of the cobalt catalyst process. This technology uses organophosphine ligands, which allows a lower operating pressure of 30–100 atm but at the expense of the catalyst activity. The Shell technology is employed primarily in the production of linear primary alcohols, whereas the high-pressure cobalt technology is frequently used in the production of branched alcohols.

Aroma threshold values

Detection: 250 ppb to 4.1 ppm

Taste threshold values

Taste characteristics at 50 ppm: fusel, fermented, fruity, banana, ethereal and cognac

General Description

Colorless liquid with a mild, choking alcohol odor. Less dense than water, soluble in water. Hence floats on water. Produces an irritating vapor.

Air & Water Reactions

Highly flammable. Water soluble.

Reactivity Profile

3-Methyl-1-butanol attacks plastics [Handling Chemicals Safely, 1980. p. 236]. Mixtures with concentrated sulfuric acid and strong hydrogen peroxide may cause explosions. Mixing with hypochlorous acid in water or water/carbon tetrachloride solution can generate isoamyl hypochlorites, which may explode, particularly on exposure to sunlight or heat. Mixing with chlorine would also yield isoamyl hypochlorites [NFPA 491 M, 1991]. Base-catalysed reactions with isocyanates can occur with explosive violence [Wischmeyer,1969].

Hazard

Moderate fire risk. Vapor is toxic and irritant. Explosive limits in air 1.2–9%.

Health Hazard

Very high vapor concentrations irritate eyes and upper respiratory tract. Continued contact with skin may cause irritation.

Biochem/physiol Actions

3-Methyl-1-butanol is a pentanol isomer useful in biofuels. It is used as a starting material for the production of isoamyl acetate, a flavoring agent applicable in the food industry. 3-Methyl-1-butanol shows anti-fungal action by inhibiting the hyphal formation and reducing biofilm formation in Candida albicans. It is also used in DNA extraction protocols.

Potential Exposure

(n-isomer); Suspected reprotoxic hazard, Primary irritant (w/o allergic reaction), (iso-, primary): Possible risk of forming tumors, Primary irritant (w/o allergic reaction), (sec-, active primary-, and other isomers) Primary irritant (w/o allergic reaction). Used as a solvent in organic synthesis and synthetic flavoring, pharmaceuticals, corrosion inhibitors; making plastics and other chemicals; as a flotation agent. The (n-isomer) is used in preparation of oil additives, plasticizers, synthetic lubricants, and as a solvent.

Environmental Fate

Biological. Using the BOD technique to measure biodegradation, the mean 5-d BOD value (mM BOD/mM isoamyl alcohol) and ThOD were 4.46 and 59.5%, respectively (Vaishnav et al., 1987).
Chemical/Physical. Isoamyl alcohol will not hydrolyze because it has no hydrolyzable functional group (Kollig, 1993).

Shipping

UN2811 Pentanols, Hazard Class: 3; Labels: 3- Flammable liquid. UN1987 Alcohols, n.o.s., Hazard Class: 3; Labels: 3-Flammable liquid.

Purification Methods

Dry the alcohol by heating with CaO and fractionally distilling, then heating with BaO and redistilling. Alternatively, boil it with concentrated KOH solution, wash it with dilute H3PO4, and dry it with K2CO3, then anhydrous CuSO4, before fractionally distilling it. If very dry alcohol is required, the distillate is refluxed with the appropriate alkyl phthalate or succinate as described for ethanol. It is separated from 2-methyl-1-butanol by fractional distillation, fractional crystallisation and preparative gas chromatography. [Beilstein 1 IV 1677.]

Incompatibilities

Forms an explosive mixture with air. Contact with strong oxidizers and hydrogen trisulfide may cause fire and explosions. Incompatible with strong acids. Violent reaction with alkaline earth metals forming hydrogen, a flammable gas.

Waste Disposal

Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber. All federal, state, and local environmental regulations must be observed.