Introduction
Benzyl alcohol, also known as benzyl alcohol, has a molecular formula of C6H5CH2OH, abbreviated as BNOH, and a density of 1.045 g/mL at 25 °C (lit.). It is the simplest fatty alcohol containing a phenyl group and can be regarded as a hydroxymethyl-substituted Benzene, or phenyl-substituted methanol. It is a colorless, transparent and viscous liquid with a faint aromatic odor. Sometimes, after benzyl alcohol has been left for a long time, it will smell like benzaldehyde and bitter almond due to oxidation.
It is polar, low-toxic, and has low vapor pressure, so it is used as an alcohol solvent. Combustible. Slightly soluble in water (about 1 gram of benzyl alcohol can be dissolved in 25 ml of water), and miscible with organic solvents such as ethanol, ether, benzene, and chloroform. Commonly used raw materials in cosmetics.
Performance and usage
Benzyl alcohol is widely used in the production of industrial chemicals. Used in paint solvents, photographic developers, polyvinyl chloride stabilizers, pharmaceuticals, synthetic resin solvents, vitamin B injection solvents, and preservatives in ointments or liquids. It can be used as a desiccant for nylon filaments, fibers and plastic films, a solvent for dyes, cellulose esters and casein, and an intermediate for preparing benzyl esters or ethers.
At the same time, it is also widely used in pen making (ballpoint pen oil), paint solvents, etc.
Benzyl alcohol is a very useful fixative and an indispensable spice in the preparation of jasmine, moonflower, ylang-ylang and other flavors. Used for preparing soaps and daily cosmetic essences. However, benzyl alcohol can slowly and naturally oxidize, and part of it generates benzaldehyde and benzyl ether, which makes commercially available products often have an almond aroma, so it should not be stored for a long time.
Regulatory requirements
In the “Safety and Technical Specifications for Cosmetics 2015”, components used as preservatives are permitted and the maximum concentration is 1%. When not used as preservatives, they are restricted components, but the maximum concentration is not given.
Preparation method
1. Benzyl alcohol naturally exists in orange blossom, ylang-ylang, jasmine, gardenia, acacia, lilac, and hyacinth. It is industrially prepared with benzyl chloride or benzaldehyde as raw materials.
Add benzyl chloride to 12% soda ash solution, heat to 93°C and stir for 5 hours, then raise the temperature to 101~103°C and continue the reaction for 10 hours. After the reaction is completed, cool to room temperature, add salt until saturated, let stand and separate into layers, take the supernatant liquid and distill it under normal pressure to obtain a crude product, which is then refined to obtain the finished product. The yield is 70% to 72%.
Benzyl alcohol is prepared through a disproportionation reaction between formaldehyde and benzaldehyde in the presence of sodium hydroxide.
2. It is obtained by heating and hydrolyzing benzyl chloride under the catalysis of alkali.
3. Mix benzyl chloride, sodium carbonate and water in a certain ratio, stir quickly to emulsify the oil layer, and raise the temperature to 90°C while stirring. When the generated carbon dioxide gas no longer escapes, continue to raise the temperature. to 101~103℃ to complete the hydrolysis reaction:
After the reaction is completed, cool and let stand to separate layers. Take the oil layer and wash it with water several times, merge it into the water layer, and then distill it under normal pressure. First, water, benzyl chloride and other low-boiling substances are evaporated as the initial fraction, and then the temperature between 203 and 206°C is collected as the main fraction, which is the finished product.
4.
In a reaction bottle equipped with a stirrer, reflux condenser, and thermometer, add 250 mL of water, 56 g of sodium carbonate, and 63.3 g (0.5 mol) of benzyl chloride (2), and stir vigorously to emulsify the benzyl chloride. Add until slightly boiling (about 95°C). Carbon dioxide is produced during the reaction. When the carbon dioxide bubbles stop escaping, the reaction is completed, and then the reaction is stirred for 0.5 h. Cool, separate the organic layer, and wash with water to obtain crude benzyl alcohol. Fractionate distillate and collect the fractions at 204-205°C to obtain 40g of benzyl alcohol with a yield of 74%.
Inspection methods
“Cosmetic Safety Technical Specifications 2015” version:
1. Gas Chromatography
2. High performance liquid chromatography
Related recipes
Example formulas in the “Cosmetic Safety Technical Specifications 2015” edition:
Preparation method: Heat phase A and phase B to 77℃-82℃ respectively, mix thoroughly using a spiral oscillator, add phase A to phase B under stirring, mix thoroughly, homogenize, and keep warm. After emulsifying for 20 minutes, cool down. When it reaches 49℃-54℃, add phase C and stir evenly. Mix thoroughly and homogenize. Slowly cool down to 35℃-41℃ to avoid evaporation of water. Cool to 27℃-32℃. Discharging and filling.
