4-benzyl alcohol

Benzyl alcohol is employed in pharmaceuticals and lacquers. This alcohol has a much weaker odor than its esters. 

Benzyl alcohol is manufactured by hydrolysis of benzyl chloride. 

Benzyl alcohol is irritant to skin and mucosa, but not a skin sensitiser and not mutagenic. Metabolism oxidation to benzoic acid and excretion as hippuric acid. 

Benzyl alcohol exhibits a broad spectrum of effectiveness which covers bacteria, yeasts and moulds. However, the activity against moulds is more intense than against bacteria (see Table 3.). The bactericidal action is slow. 

Benzyl alcohol is listed in the EC positive list of preservatives for cosmetic products (maximum concentration for application 10.000 mg/litre) as a preservative it may be useful also in pharmaceutical preparations. Percentage of use in US cosmetic formulations 0.32%. The activity of benzyl alcohol is not very much affected by the pH and the composition of the medium to be protected. As an auxiliary solvent with antimicrobial efficacy benzyl alcohol is used in preservative compositions for industrial fluids (Paulus et al., 1970a). A well-known preservative for cosmetics and industrial fluids is benzyl alcohol mono(poly)hemiformal (Paulus, 1976) which is a formaldehyde releasing compound and therefore listed under 3.1.2. 

Microbicide group (substance class) Chemical name Chemical formula Structural formula 

Boiling point/range C (101 kPa) Melting point C Flash point C Stability 

BP Benzyl alcohol JP Benzyl alcohol PhEur Alcohol benzylicus USPNF Benzyl alcohol 

Benzenemethanol a-hydroxytoluene phenylcarbinol phenyl-methanol a-toluenol. 

Benzyl alcohol is an antimicrobial preservative used in cosmetics, foods, and a wide range of pharmaceutical formulations, including oral and parenteral preparations, at concentrations up to 2.0% v/v. In cosmetics, concentrations up to 3.0% v/v may be used as a preservative. Concentrations of 5% v/v or more are employed as a solubilizer, while a 10% v/v solution is used as a disinfectant. 

Benzyl alcohol 10% v/v solutions also have some local anesthetic properties, which are exploited in some parenterals, cough products, ophthalmic solutions, ointments, and dermatological aerosol sprays. 

Although widely used as an antimicrobial preservative, benzyl alcohol has been associated with some fatal adverse reactions when administered to neonates. It is now recommended that parenteral products preserved with benzyl alcohol, or other antimicrobial preservatives, should not be used in newborn infants if at all possible see Section 14. 

Preparation of Benzyl Alcohol from Benzaldehyde (Section 523).—Place in a 250-cc. bottle 20 grams of benzaldehyde and a cold solution of 18 grams of potassium hydroxide in 12 cc. 

Benzyl alcohol boils at 206°. The yield in the preparation should be about 7 grams. 

Add an excess of hydrochloric acid to the filtered aqueous solution of potassium benzoate, filter off the precipitate of benzoic acid, and wash it with cold water. Crystallize the acid from boiling water. Weigh the acid and calculate the percentage yield. 

Properties of Benzyl Alcohol (SECTION 523).—(a) Benzyl alcohol and hydrochloric acid.—Mix 2 cc. of benzyl alcohol and 4 cc. of concentrated hydrochloric acid. Heat the mixture slowly and note any change produced. (Eq.) Observe the odor of the substance formed. 

Synonyms phenyl methanol phenyl carbi-nol benzene carbinol benzoyl alcohol a-hydroxytoluene a-toluenol 

Esters of benzyl alcohol are used in making perfume, soap, flavoring, lotion, and ointment. It finds application in color photography the pharmaceuticals industry, cosmetics. 

Compound/CAS No. Structure/Functional Group Physical Properties and Solubility in water Uses Toxicity 

2-Methyl-3-butyn-2-ol OH Liquid bp 103.6°C In making isoprene. Low toxicity  

3-Methyl-l -pentyn-3-ol OH Liquid bp 121.4°C In the production of Moderately toxic  

Warm i c. i. of the alcohol with i c.c. concentrated hydio-cbloric acid. I liechnir solution becomes turbid and benzyl cliloride sepni ntes oni. 

Compounds that have a hydroxyl group attached to a chain on a benzene ring are called aromatic alcohols. These alcohols differ from phenols and show similar properties to aliphatic alcohols. The most important aromatic alcohols are benzyl alcohol and (3-phenyl ethyl alcohol. 

This is the simplest member of the aromatic alcohols. It is isomeric with cresol. 

Its oxidation products are benzaldehyde and benzoic acid, respectively. 

It is a colorless liquid with a pleasant odor and has a boiling point of 205 °C. 

The benzyl alcohol structure contains both the aliphatic and aromatic groups. Although it is an alcohol, it dissolves in organic solvents and is only slightly soluble in water. It reacts with Na and K to produce H2 as phenols and cresols do. However, phenols and cresols are differentiated from benzyl alcohol by their reaction with NaOH. Esters of benzyl alcohols also have a nice, pleasant odor. 

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It is readily oxidized by air to benzoic acid. With aqueous KOH gives benzyl alcohol and benzoic acid. Gives addition products with hydrogen cyanide and sodium hydrogen sulphite. 

It is prepared by the direct chlorination of toluene in the presence of PClj. It is purified by fractionation from the unchanged toluene and the higher chlorinated products. It is used for benzylating amines and for preparing benzyl alcohol. 

Cannizzaro reaction Two molecules of many aldehydes, under the influence of dilute alkalis, will interact, so that one is reduced to the corresponding alcohol, while the other is oxidized to the acid. Benzaldehyde gives benzyl alcohol and benzoic acid. Compare the aldol condensation. 

Benzyl Alcohol, CeH5CH20H, and Benzoic Acid, CaHsCOOH. (Cannizzaro s Reaction). 

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... 

Alcohols. Methanol, ethanol, n propanol, propan-i-ol.n-butanol, glycol, glycerol, benzyl alcohol, cyclohexanol. 

Undergoes Cannizzaro s reaction, giving benzyl alcohol and benzoic acid (p. 229). Warm gently for several minutes, cool, add a few ml. of water and then cone. HCl, and cool again. Crystals of benzoic acid separate out on scratching the sides of the tube with a glass rod. 

Physical Properties. All colourless liquids, completely miscible with water, except benzyl alcohol and cyclohexanol, which are slightly soluble. Pure glycol and glycerol have high viscosity, which falls as the hygroscopic liquids absorb water from the air. 

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 . 

C) Carboxylic adds For aryl-substituted alcohols, such as benzyl alcohol, oxidation readily gives the corresponding add (c/. p. 336). 

Almost insoluble in cold water. Higher alcohols (including benzyl alcohol), higher phenols (e.g., naphthols), metaformaldehyde, paraldehyde, aromatic aldehydes, higher ketones (including acetophenone), aromatic acids, most esters, ethers, oxamide and domatic amides, sulphonamides, aromatic imides, aromatic nitriles, aromatic acid anhydrides, aromatic acid chlorides, sulphonyl chlorides, starch, aromatic amines, anilides, tyrosine, cystine, nitrocompounds, uric acid, halogeno-hydrocarbons, hydrocarbons. 

CH3COOH + C.HsCHjOH Acetic acid Benzyl alcohol... 

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. 

Benzyl alcohol. This alcohol, b.p. 205-5°, may be similarly prepared from benzaldehyde in approximately the same yield (compare Section IV, 123.)... 

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. 

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