Isoamyl

Isovaleric acid, Me2CHCH2COOH, is a colourless liquid with the unpleasant odour of valerian, b.p. 177 "C. Occurs in the roots of valerian and angelica together with an optically active form of methylethylethanoic acid. Prepared by oxidation of isoamyl alcohol. A mixture of acids similar to that obtained from valerian roots is prepared by oxidation of fusel oil. 

IsoValeric acid. Prepare dilute sulphuric acid by adding 140 ml. of concentrated sulphuric acid cautiously and with stirring to 85 ml. of water cool and add 80 g. (99 ml.) of redistilled woamyl alcohol. Place a solution of 200 g. of crystallised sodium dicliromate in 400 ml. of water in a 1-litre (or 1-5 litre) round-bottomed flask and attach an efficient reflux condenser. Add the sulphuric acid solution of the isoamyl alcohol in amaU portions through the top of the condenser shake the apparatus vigorously after each addition. No heating is required as the heat of the reaction will suffice to keep the mixture hot. It is important to shake the flask well immediately after each addition and not to add a further portion of alcohol until the previous one has reacted if the reaction should become violent, immerse the flask momentarily in ice water. The addition occupies 2-2-5 hours. When all the isoamyl alcohol has been introduced, reflux the mixture gently for 30 minutes, and then allow to cool. Arrange the flask for distillation (compare Fig. II, 13, 3, but with the thermometer omitted) and collect about 350 ml. of distillate. The latter consists of a mixture of water, isovaleric acid and isoamyl isovalerate. Add 30 g. of potassium not sodium) hydroxide pellets to the distillate and shake until dissolved. Transfer to a separatory funnel and remove the upper layer of ester (16 g.). Treat the aqueous layer contained in a beaker with 30 ml. of dilute sulphuric acid (1 1 by volume) and extract the liberated isovaleric acid with two... 

Since (A) does not contain any other functional group in addition to the formyl group, one may predict that suitable reaction conditions could be found for all conversions into (A). Many other alternative target molecules can, of course, be formulated. The reduction of (H), for example, may require introduction of a protecting group, e.g. acetal formation. The industrial synthesis of (A) is based upon the oxidation of (E) since 3-methylbutanol (isoamyl alcohol) is a cheap distillation product from alcoholic fermentation ( fusel oils ). The second step of our simple antithetic analysis — systematic disconnection — will now be exemplified with all target molecules of the scheme above. For the sake of brevity we shall omit the syn-thons and indicate only the reagents and reaction conditions. 

Methyl-5-aminothia2ole-4-carboxylic acid is diazotized with isoamyl nitrite in the presence of furan in 1.2-dichloroethane to give a mixture of products 163 (53%), 164 (33%). 165 (11%), and 166 (3%) (Scheme 104) (334). This reactivity experiment was carried out to examine the possibility of the occurrence of 4,5-dehydrothiazole (hetaryne). Hetaryne intermediates seem not to be involved as an intermediate in the reaction. The formation of 163 through 166 can be rationalized in terms of the intermediacy of 166a. 

Attempts to obtain thiazolynes by treating 5-aminothiazoles with isoamyl nitrite in ethylene chloride were unsuccessful (334). 

In agreement with the theory of polarized radicals, the presence of substituents on heteroaromatic free radicals can slightly affect their polarity. Both 4- and 5-substituted thiazol-2-yl radicals have been generated in aromatic solvents by thermal decomposition of the diazoamino derivative resulting from the reaction of isoamyl nitrite on the corresponding 2-aminothiazole (250,416-418). Introduction in 5-position of electron-withdrawing substituents slightly enhances the electrophilic character of thiazol-2-yl radicals (Table 1-57). 

Handbooks are notorious for listing compounds according to their common names One gives the name sec isoamyl alcohol for a compound which could be called 1 2 dimethylpropyl alcohol according to the lUPAC functional class rules The best name for this compound is the substitutive lUPAC name What is it" ... 

Isoamyl acetate is the common name of the substance most responsible for the characteris tic odor of bananas Wnte a structural formula for isoamyl acetate given the information that it IS an ester in which the carbonyl group bears a methyl substituent and there is a 3 methylbutyl group attached to one of the oxygens... 

Methylbutyl acetate is more commonly known as isoamyl acetate... 

Anhydrous Acetic Acid. In the manufacture of acetic acid by direct oxidation of a petroleum-based feedstock, solvent extraction has been used to separate acetic acid [64-19-7] from the aqueous reaction Hquor containing significant quantities of formic and propionic acids. Isoamyl acetate [123-92-2] is used as solvent to extract nearly all the acetic acid, and some water, from the aqueous feed (236). The extract is then dehydrated by azeotropic distillation using isoamyl acetate as water entrainer (see DISTILLATION, AZEOTROPIC AND EXTRACTIVE). It is claimed that the extraction step in this process affords substantial savings in plant capital investment and operating cost (see Acetic acid and derivatives). A detailed description of various extraction processes is available (237). 

Miscellaneous Pharmaceutical Processes. Solvent extraction is used for the preparation of many products that ate either isolated from naturally occurring materials or purified during synthesis. Among these are sulfa dmgs, methaqualone [72-44-6] phenobarbital [50-06-6] antihistamines, cortisone [53-06-5] estrogens and other hormones (qv), and reserpine [50-55-5] and alkaloids (qv). Common solvents for these appHcations are chloroform, isoamyl alcohol, diethyl ether, and methylene chloride. Distribution coefficient data for dmg species are important for the design of solvent extraction procedures. These can be determined with a laboratory continuous extraction system (AKUEVE) (244). 

Other food lures which have had practical use ia trapping insect pests include isoamyl saUcylate [87-20-7] for moths of the tomato and tobacco homworms, Manduca spp. heptyl butyrate [5870-93-0] for stinging yeUowjackets, Vespula spp. and l-octene-3-ol [3391-86-4] for the bloodsucking tsetse dies, Glossina spp. 

Methyl Isoamyl Ketone. Methyl isoamyl ketone [110-12-3] (5-methyl-2-hexanone) is a colorless Hquid with a mild odor. It is produced by the condensation of acetone and isobutyraldehyde (164) in three steps which proceed via the keto-alcohol dehydration to 5-methyl-3-hexen-2-one, and hydrogenation to 5-methyl-2-hexanone. 

Isobutyraldehyde is commonly available as a by-product of propylene/Oxo hydroformylation. Methyl isoamyl ketone is used as a solvent for ceUulose esters, acryHcs, and vinyl polymers. It is available in the United States from Eastman (Kingsport, Tennessee) (47) and Union Carbide (South Charleston, West Virginia) and was priced at 1.42/kg in October 1994. 

Other Higher Oleiins. Linear a-olefins, such as 1-hexene and 1-octene, are produced by catalytic oligomerization of ethylene with triethyl aluminum (6) or with nickel-based catalysts (7—9) (see Olefins, higher). Olefins with branched alkyl groups are usually produced by catalytic dehydration of corresponding alcohols. For example, 3-methyl-1-butene is produced from isoamyl alcohol using base-treated alumina (15). 

Other appHcations of amyl alcohols include their use as flavor and fragrance chemicals. Amyl isovalerate and amyl saHcylate consumed a maximum of 450 t of amyl alcohols (150). Isoamyl saHcylate is used to a large extent in soap and cosmetic fragrances because of its cost effectiveness (167). Isoamyl... 

Factors affecting the accumulation of ansamitocins P-2, P-3, and P-4 in JSbocardia sp. C-15003 have been studied (246) the addition of isoleucine, propionate, ptopionaldehyde, or -ptopyl alcohol to the fermentation medium resulted in the increased production of P-2 the addition of valine, isobutyrate, isobutyraldehyde, or isobutyl alcohol increased the production of P-3, reaching more than 90% of the total ansamitocins produced and the addition of leucine, isovalerate, isovaleraldehyde, or isoamyl alcohol increased the production of P-4. 

Isoamyl saUcylate is perhaps the most important ester of saUcyhc acid for perfumery purposes. Generally, it is manufactured by the transesterification of methyl saUcylate. It has a characteristic flowery aroma and is useful in soap fragrances. The May 1996 price was 5.30/kg (18). Other saUcylates of commercial interest as flavor and fragrance agents include isopropyl, isobutyl, phenethyl [87-22-9] and 2-ethyIhexyl saUcylates. 

Anhydrous stannous chloride, a water-soluble white soHd, is the most economical source of stannous tin and is especially important in redox and plating reactions. Preparation of the anhydrous salt may be by direct reaction of chlorine and molten tin, heating tin in hydrogen chloride gas, or reducing stannic chloride solution with tin metal, followed by dehydration. It is soluble in a number of organic solvents (g/100 g solvent at 23°C) acetone 42.7, ethyl alcohol 54.4, methyl isobutyl carbinol 10.45, isopropyl alcohol 9.61, methyl ethyl ketone 9.43 isoamyl acetate 3.76, diethyl ether 0.49, and mineral spirits 0.03 it is insoluble in petroleum naphtha and xylene (2). 

When exposed to ait, the sodium salts tend to take up moisture and form dihydrates. The alkah metal xanthates are soluble ia water, alcohols, the lower ketones, pyridine, and acetonitrile. They are not particularly soluble ia nonpolar solvents, eg, ether or ligroin. The solubiUties of a number of these salts are Hsted ia Table 4. Potassium isopropyl xanthate is soluble ia acetone to ca 6 wt %, whereas the corresponding methyl, ethyl, / -propyl, n-huty isobutyl, isoamyl, and benzyl [2720-79-8] xanthates are soluble to more than 10 wt % (12). The solubiUties of the commercially available xanthates ia water are plotted versus temperature ia Figure 1 (14). 

---