Methylbenzyl alcohol

Checked by William S. Johnson, Donald W. Stoutamire, and A. L. Wilds. 

o-Methylbenzyl acetate. A solution of 29.8 g. (0.20 mole) of 2-methylbenzyldimethylamine 2 and 32.7 g. (0.30 mole) of ethyl bromide in 40 ml. of absolute ethanol is placed in a 500-ml. round-bottomed flask fitted with a reflux condenser capped with a calcium chloride drying tube. The solution is heated under reflux on the steam bath for 1 hour then an additional 10.8 g. (0.10 mole) of ethyl bromide is added and the heating continued for an additional 3 hours. The solvent and residual ethyl bromide are removed at reduced pressure (water aspirator) while the flask is heated in a water bath kept at about 60° (Note 1). The oily residue is treated with about 300 ml. of absolute ether, and on scratching crystallization is induced. The product is collected on a Buchner funnel, washed with two 50-ml. portions of anhydrous ether, and dried in a vacuum desiccator. The yield of colorless 2-methylbenzylethyldimethylammonium bromide is 47.5-49.0 g. (92-95%) (Note 2). It is hygroscopic and should therefore not be exposed to moist air. 

In a 500-ml. round-bottomed flask, fitted with a reflux condenser capped with a calcium chloride drying tube, are placed 

15 mole) of the quaternary ammonium bromide (Note 3) described above, 24.6 g. (0.3 mole) of fused sodium acetate, and 100 ml. of glacial acetic acid. The mixture is boiled under reflux for 24 hours (Note 4) and then allowed to cool. It is transferred to a large beaker (Note 5), 250 ml. of water is added, and the acid is partially neutralized by the addition of 84 g. of solid sodium bicarbonate. The mixture is extracted with three 75-ml. portions of ether, and the combined ether solutions are washed with two or more 50-ml. portions of saturated sodium bicarbonate solution until all the acetic acid has been removed. The ether layer is then washed with 50 ml. of saturated sodium chloride solution and dried over anhydrous sodium sulfate. The ether is removed by distillation, and the residue is distilled under reduced pressure. The yield of colorless liquid acetate, b.p. 119—121 °/15 mm. or 129-131°/31 mm., is 21.6-22.4 g. (88-91%), 1.5041- 

o-Methylbenzyl alcohol. A solution of 5 g. (0.12 mole) of sodium hydroxide in 50 ml. of water is added to a solution of 16.4 g. (0.1 mole) of 2-methylbenzyl acetate (prepared as described above, part A) in 50 ml. of methanol contained in a 250-ml. round-bottomed flask fitted with a reflux condenser. The mixture is boiled under reflux for 2 hours, cooled, diluted with 50 ml. of water, and extracted with three 75-ml. portions of ether. The combined ether solutions are washed with 50 ml. of water and 50 ml. of saturated sodium chloride solution and dried over anhydrous sodium sulfate. The solvent is removed by distillation, finally at reduced pressure to remove the last traces of methyl alcohol, and the residue is dissolved in 50 ml. of boiling 30-60° petroleum ether. The colorless crystals obtained on cooling, finally in the ice bath, are collected by suction filtration, washed with a few milliliters of cold petroleum ether, and air-dried. Concentration of the mother liquors to 6-7 ml. and cooling gives an additional crop. The total yield of product melting between 33-34° and 35-36° is 11.6-11.8 g. (95-97%) (Note 7). 

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The catalyst is inactive for the hydrogenation of the (isolated) benzene nucleus and so may bo used for the hydrogenation of aromatic compounds containing aldehyde, keto, carbalkoxy or amide groups to the corresponding alcohols, amines, etc., e.g., ethyl benzoate to benzyl alcohol methyl p-toluate to p-methylbenzyl alcohol ethyl cinnamate to 3 phenyl 1-propanol. 

Propylene oxide [75-56-9] is manufactured by either the chlorohydrin process or the peroxidation (coproduct) process. In the chlorohydrin process, chlorine, propylene, and water are combined to make propylene chlorohydrin, which then reacts with inorganic base to yield the oxide. The peroxidation process converts either isobutane or ethylbenzene direcdy to an alkyl hydroperoxide which then reacts with propylene to make propylene oxide, and /-butyl alcohol or methylbenzyl alcohol, respectively. Table 1 Hsts producers of propylene glycols in the United States. 

Hyperbranched polyurethanes are constmcted using phenol-blocked trifunctional monomers in combination with 4-methylbenzyl alcohol for end capping (11). Polyurethane interpenetrating polymer networks (IPNs) are mixtures of two cross-linked polymer networks, prepared by latex blending, sequential polymerization, or simultaneous polymerization. IPNs have improved mechanical properties, as weU as thermal stabiHties, compared to the single cross-linked polymers. In pseudo-IPNs, only one of the involved polymers is cross-linked. Numerous polymers are involved in the formation of polyurethane-derived IPNs (12). 

FIGURE 22.8 The 200-MHz H NMR spectra of (a) 4-methylbenzylamine and ( )) 4-methylbenzyl alcohol. The singlet corresponding to CH2N in (a) is more shielded than that of CH2O in (b). 

Charlton121 has recently reported the asymmetric induction in the reaction of dimethyl fumarate and l,3-dihydrobenzo[c]thiophene 2,2-dioxide (198) containing a chiral a-alkoxy group at the 2-position (equation 128). A diastereomeric excess of 2.8 1 of 199 to 200 is achieved by using 198 derived from optically active a-methylbenzyl alcohol. 

Amino-a-methylbenzyl alcohol, a256 2-Amino-3-methylpentanoic acid, i88 2-Amino-2-methylpropane, b511... 

Five kinds of methylbenzyl alcohols were prepared through the following routes ... 

Benzyl alcohols, including commercially available benzyl alcohol and 4-methylbenzyl alcohol, were purified through rectification, followed by recrystallization when the alcohols were solids. 

In most cases, the reaction was carried out with formic acid. However, p-toluenesulfonic acid was used for the condensation of 4-methylbenzyl alcohol with benzene, benzyl alcohol with isodurene, and 2-methylbenzyl alcohol with p-xylene because formic acid was too weak an acid in these cases. 

The reactor effluent is distilled and unreacted EB is recycled. The EB hydroperoxide is then reacted with propylene at 250°F and pressure in the range of 250-700 psi in the presence of a metal catalyst to produce propylene oxide and methylbenzyl alcohol B in Figure 8-7). The reactor mixture is separated by multiple fractionators. Unreacted propylene and EB are recycled. PO is recovered overhead. The methyl benzyl alcohol is easily dehydrated in the vapor stage at 450—500° F and 500 psi pressure over a titanium dioxide or silica gel catalyst to form styrene. Acephenone is one of the by-products. 

Biological. A proposed microbial degradation mechanism is as follows 4-hydroxy-3-methylbenzyl alcohol to 4-hydroxy-3-methylbenzaldehyde to 3-methyl-4-hydroxybenzoic acid to 4-hydroxyisophthalic acid to protocatechuic acid to p ketoadipic acid (Chapman, 1972). In anaerobic sludge, diethyl phthalate degraded as follows monoethyl phthalate to phthalic acid to protocatechuic acid followed by ring cleavage and mineralization (Shelton et al, 1984). 

Powerful complex hydrides like lithium aluminum hydride in refluxing ether [5i] or refluxing tetrahydrofuran [1017] reduce cyclic anhydrides to diols. Phthalic anhydride was thus transformed to phthalyl alcohol (o-hydroxy-methylbenzyl alcohol) in 87% yield [5i]. Similar yields of phthalyl alcohol were obtained from phthalic anhydride and sodium bis 2-methoxyethoxy) aluminum hydride [544, 969]. 

Methylbenzyl alcohol 529 can just about be lithiated by treatment with BuLi in EtiO at room temperature, but the activation of the methyl group is very weak. Lateral lithiation of cresol 530 is even harder to achieve, and the superbase conditions required... 

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