Of benzylic alcohols

A crystalline derivative of benzyl alcohol cannot be obtained by using benzoyl chloride, because the benzyl benzoate, C HiCOOCHiCaHj, so obtained has m.p. 18°, and is thus usually liquid the present preparation illustrates therefore the use of a substituted benzoyl chloride (p-nitrobenzoyl chloride, m.p. 75°) in order to obtain a crystalline derivative of suitably high m.p. 

Place I ml. of benzyl alcohol in a boiling-tube and add 6 ml. of 10% sodium hydroxide solution add also 6 ml. of water to moderate the subsequent reaction, otherwise the rise in temperature may cause hydrolysis of some of the ester produced. Now add r-q g. of finely powdered />-nitrobenzoyl chloride, and shake the well-corked tube vigorously. The mixture becomes warm, and the solid ester rapidly... 

Glycol and glycerol are odourless the other alcohols have faint odours, that of benzyl alcohol being characteristic. 

Example. Add a solution of 0 5 ml. of benzyl alcohol in 5 ml. of petroleum (b.p. 100-120 ) to a similar solution of 0 5 ml. of phenylisocyanate, and boil the mixture gently under reflux for 20 minutes. Filter hot if necessary from any insoluble diphenylurea, and cool. Filter off the crystalline urethane, and recrystallise from the petroleum colourless crystals, m.p. 76 . 

Mix 31 g. (29-5 ml.) of benzyl alcohol (Section IV, 123 and Section IV,200) and 45 g. (43 ml.) of glacial acetic acid in a 500 ml. round-bottomed flask introduce 1 ml. of concentrated sulphuric acid and a few fragments of porous pot. Attach a reflux condenser to the flask and boil the mixture gently for 9 hours. Pour the reaction mixture into about 200 ml. of water contained in a separatory funnel, add 10 ml. of carbon tetrachloride (to eliminate emulsion formation owing to the slight difference in density of the ester and water, compare Methyl Benzoate, Section IV,176) and shake. Separate the lower layer (solution of benzyl acetate in carbon tetrachloride) and discard the upper aqueous layer. Return the lower layer to the funnel, and wash it successively with water, concentrated sodium bicarbonate solution (until effervescence ceases) and water. Dry over 5 g. of anhydrous magnesium sulphate, and distil under normal pressure (Fig. II, 13, 2) with the aid of an air bath (Fig. II, 5, 3). Collect the benzyl acetate a (colourless liquid) at 213-215°. The yield is 16 g. 

Section 1115 The simplest alkenylbenzene is styrene (C6H5CH=CH2) An aryl group stabilizes a double bond to which it is attached Alkenylbenzenes are usu ally prepared by dehydration of benzylic alcohols or dehydrohalogena tion of benzylic halides... 

The —OH proton of a primary alcohol RCH2OH is vicinal to two protons and its sig nal would be expected to be split into a triplet Under certain conditions signal splitting of alcohol protons is observed but usually it is not Figure 13 21 presents the NMR spec trum of benzyl alcohol showing the methylene and hydroxyl protons as singlets at 8 4 7 and 2 5 respectively (The aromatic protons also appear as a singlet but that is because they all accidentally have the same chemical shift and so cannot split each other)... 

MHz H NMR spectrum of benzyl alcohol The hydroxyl proton and the methylene protons are vicinal but do not split each other because of the rapid intermolecular exchange of hydroxyl protons... 

The alternative synthetic route using the sodium salt of benzyl alcohol and an isopropyl halide would be much less effective because of increased competition from elimination as the alkyl halide becomes more sterically hindered... 

The only industrially important processes for the manufacturing of synthetic benzaldehyde involve the hydrolysis of benzal chloride [98-87-3] and the air oxidation of toluene. The hydrolysis of benzal chloride, which is produced by the side-chain chlorination of toluene, is the older of the two processes. It is no longer utilized ia the United States. Other processes, including the oxidation of benzyl alcohol, the reduction of benzoyl chloride, and the reaction of carbon monoxide and benzene, have been utilized ia the past, but they no longer have any iadustrial appHcation. 

Table 1. Physical Properties of Benzyl Alcohol and p-Phenethyl Alcohol...

Prior to the commercial development of this process benzyl alcohol was obtained from benzaldehyde [100-52-7] which undergoes the Cannizzaro reaction (2) upon treatment with potassium hydroxide. High yields of benzyl alcohol and potassium benzoate are obtained by this route which cannot compete with the present day process because of the high cost of benzaldehyde (qv). 

The NF and reagent grades are employed in the pharmaceutical industry which makes use of benzyl alcohol s local anesthetic, antiseptic, and solvent properties (17—20). It also finds use in cough symps and drops ophthalmic solutions bum, dental (21), and insect repeUant solutions and ointments and dermatological aerosol sprays. It is used in nail lacquers and as a color developer in hair dyes by the cosmetics industry (22), and in acne treatment preparations (23). 

Nearly all uses and appHcations of benzyl chloride are related to reactions of the active haUde substituent. More than two-thirds of benzyl chloride produced is used in the manufacture of benzyl butyl-phthalate, a plasticizer used extensively in vinyl flooring and other flexible poly(vinyl chloride) uses such as food packaging. Other significant uses are the manufacture of benzyl alcohol [100-51-6] and of benzyl chloride-derived quaternary ammonium compounds, each of which consumes more than 10% of the benzyl chloride produced. Smaller volume uses include the manufacture of benzyl cyanide [140-29-4], benzyl esters such as benzyl acetate [140-11-4], butyrate, cinnamate, and saUcylate, benzylamine [100-46-9], and benzyl dimethyl amine [103-83-8], and -benzylphenol [101-53-1]. In the dye industry benzyl chloride is used as an intermediate in the manufacture of triphenylmethane dyes (qv). First generation derivatives of benzyl chloride are processed further to pharmaceutical, perfume, and flavor products. 

IQ. To determine the concentration of chloride ion, - a 5-mL aliquot of the methyl lithium solution is cautiously added to 25 ml of water and the resulting solution is acidified with concentrated sulfuric acid and then treated with 2-3 ml of ferric ammonium sulfate [Fe(NH4)( 04)2 12 H2O] indicator solution and 2-3 ml of benzyl alcohol. The resulting mixture is treated with 10.0 mL of standard aqueous 0.100 M silver nitrate solution and then titrated with standard aqueous 0.100 H potassium thiocyanate solution to a brownish-red endpoint. 

The use of benzyl alcohol as solvent produces the dibenzyl acetal at C-21, and this can be reductively removed to produce the 21-hydroxy compound... 

A one-pot conversion of benzyl alcohols to benzyl fluorides by treatment of the alcohols with a combination of methanesulfonyl fluoride, cesium fluoride and 18-crown 6 ether in tetrahydrofuran has been repotted The reaction involves mesylation of the alcohols followed by cleavage of the resultant mesyl esters with a fluoride ion The reaction has been extended also to certain heterocycles bearing the N hydroxymethyl group [43] (equation 31)... 

The enol ether formed by a reaetion of benzyl alcohol with perfluorocyclo-pentene is transformed on heating in the presence of concentrated sulfunc acid into a fluorinated enol [25] (equation 22)... 

Acid-catalyzed dehydration of benzylic alcohols is a useful route to alkenylbenzenes, as is dehydrohalogenation under E2 conditions. 

HBr, AcOH, reflux, 30 min, 85%. The efficiency of this method is significantly improved if a phase transfer catalyst ( -Ci6H33P Bu3 Br ) is added to the mixture. Methods that use HBr for ether cleavage can give bromides in the presence of benzylic alcohols. ... 

It appeared that the impure alcohol isolated from balsam of Peru was, in fact, identical with nerolidol. When allowed to stand for three to four weeks with phenyl-isocyanate both alcohols yielded a phenyl-urethane, melting at 37" to 38°. A mixture of the two bodies suffered no depression in melting-point. The alcohols have the formula 15 260-The alcohol from balsam of Peru is therefore mixed with a small quantity -of an alcohol of higher specific gravity, the nature of which is still undetermined. Traces of benzyl alcohol were found in it, but not in sufficient quantity to account for the differences observed. Oxidation experiments did not throw any light on the question. It may therefore be safely assumed that the peruviol of Thoms consisted in the main of nerolidol, but contaminated with a substance of the same boiling-point to such an extent that its combustion figures pointed to the formula CjjH. jO instead of... 

Benzyl Ginnamate.—The cinnamic acid ester of benzyl alcohol is a natural constituent of storax, tolu, and Peru balsams. It is a crystalline Bubstance with a characteristic sweet balsamic odour. It may be prepared by heating sodium cinnamate, alcohol, and benzyl chloride together under a reflux condenser. It is a useful ester where a sweet balsamic odour is required to be introduced into a perfume, especially cf the heavy type. It forms white, glistening prisms, which melt at 39°, and.decompose when heated to 350°. The best commercial specimens have the following characters —... 

Benzaldehyde, a flavoring agent, is obtained by the dehydrogenation of benzyl alcohol. 

Under the same conditions, benzaldehyde yielded 80 per cent of benzyl alcohol and piperonal 86 per cent of piperonyl alcohol. 

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