Hydrogens 4-Methyl-2-pentanol

FIGURE 7.25 spectrum of 4-methyl-2-pentanol showing diastereotopic methyl and methylene groups (500 MHz, CDCI3). 

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FIGURE 7.27 Splitting diagrams for the diastereotopic methylene protons in 4-methyl-2-pentanol. 

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Reduction. Most ketones are readily reduced to the corresponding secondary alcohol by a variety of hydrogenation processes. The most commonly used catalysts are palladium, platinum, and nickel For example, 4-methyl-2-pentanol (methyl isobutyl carbinol) is commercially produced by the catalytic reduction of 4-methyl-2-pentanone (methyl isobutyl ketone) over nickel. 

The trialkylborane is oxidized by the addition to the stirred reaction mixture of 32 ml of a 3 solution of sodium hydroxide, followed by the dropwise addition of 32 ml of 30 % hydrogen peroxide at a temperature of 30-32° (water bath). The reaction mixture is saturated with sodium chloride and the tetrahydrofuran layer formed is separated and washed with saturated sodium chloride solution. The organic solution is dried over anhydrous magnesium sulfate and the THF is removed. Distillation affords 24.5 g (80%) of 4-methyl-1-pentanol, bp I51-153°/735 mm. 

The carbonyl functionality of MIBK can be hydrogenated over nickel catalysts to yield methyl isobutyl carbinol (4-methyl-2-pentanol or methyl amyl alcohol) [108-11-2]. Industrial processes coproduce methyl isobutyl carbinol during the hydrogenation of mesityl oxide to MIBK. The product ratio of methyl isobutyl carbinol—MIBK during this reaction can be shifted toward methyl isobutyl carbinol by adopting a higher than normal pressure and H2 organic ratio (59). Methyl isobutyl carbinol is used as an ore flotation frother and to produce zinc dialkyl dithiophosphate lube oil additives. It is produced in the United States by Shell and Union Carbide ( 1.12/kg, October 1994). 

Amino-l,l,l-trifluoro-4-methyl-2-pentanol hydrogen chloride (20g) was dissolved in 480 ml THF, 4-methylmorpholine (21.8 g) added followed by 7.7 ml chloroacetyl chloride 40 ml in THF, and the mixture stirred overnight. The reaction mixture was filtered, the product extracted with EtOAc, purified by chromatography with CHjClj/methyl alcohol, 95 5, and the product isolated. MS data supplied. 

Both exo- and endo-cyclic alicyclic and heterocyclic ketones have been reduced. Important examples are found in the preparations of cyclo-pentanol (95%), cycloheptanol (92%), /S-pyridylmethylcarbinol (85%), and l-alkyl-4-piperidinols (90%). A comparison of four reagents—sodium and alcohol, lithium aluminum hydride, hydrogen and Raney nickel, and hydrogen and copper-chromium oxide—has been made in the preparation of methyl cyclopropylcarbinol. The last method is superior for the preparation of this compound (SH)%). ... 

Reaction with trialkylboranes. Lane and Brown in 1971 reported a simple procedure for synthesis of highly substituted alcohols from trialkylboranes. For example, bromination of triethylboranc (1) under irradiation in the presence of water followed by oxidation with alkaline hydrogen peroxide gives 3-methyl-3-pentanol (2) in 88% yield. The reaction involves as the first step free-radical bromination in the a-position... 

Diastereoselective exchange of iodine for hydrogen has been effected by reaction of O-protected l,l-diiodo-4-methyl-3-pentanol derivatives 51 with dialkylmagnesium or alkyl... 

Remark. Pentanols or amyl alcohols, and more specifically 1-pentanok 2-methyl 1-butanol, and 3-methyl 1-butanol, do not enjoy the industrial importance of the above alcohols. They are prepared by Oxo synthesis and hydrogenation from n-butenes and isobutene. They are used as solvents and their esters as perfumes. 

METHYL-4-PENTANOL (108-11-2) Forms explosive mixture with air (flash point 106°F/41°C). Contact with alkali metals produces flammable hydrogen gas. Reacts, possibly violently, with oxidizers, acetaldehyde, alkaline earth metals, strong acids, strong caustics, aliphatic amines, benzoyl peroxide, chromic acid, chromium trioxide, dialkylzincs, dichlorine oxide, ethylene oxide, hypochlorous acid, isocyanates, isopropyl chlorocarbonate. 

Pentanol, 4-methyl-, hydrogen phosphorodithioate. Bls(1,3-dimethylbu l) dithiophosphate 0,0-Bis(1,3-dimethylbutyl) phosphorodithioate EINECS 227-900-8 2-Pentanol, 4-methyl-, hydrogen phosphorodithioate 2-Pentanol, 4-melhyl-, 0,0-dlester with phosphorodithioic acid. 

It has been observed in agreement with Gon Seo and coworkers [5] that in the gas-phase hydrogenation of furfural the products formed are 2-methyl-furan, furfUryl alcohol and (at higher temperatures) traces of tetrahydro-furfuryl alcohol. Analysis with GLC-MS showed that in the hydrogenation over the (un)promoted platinum catalysts used in this study besides 2-methyl-furan also furan was formed. Resinous material and ring-decomposed products, like 1-pentanol and 1,5-pentadiol, can also be foimd in liquid-phase hydrogenation reaction [3]. The study of Gon Seo et al. concerned the role of copper in various copper-chromium oxides and in Pd-CuY and Ni-CuY zeolite catalysts. The... 

Ans. Butanoic acid > 1-pentanol > pentanal > methyl propanoate > hexane. The order is based on differences in intermolecular forces since the compounds have very nearly the same molecular mass. Butanoic acid and 1-pentanol have hydrogen bonding but that in the acid is more extensive because of the special interaction between the carbonyl and HO groups. Aldehydes boil higher than esters because the polarity of the carbonyl group is greater than that of an ester group. The attractive forces in alkanes, the dispersion forces, are the weakest. 

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