Benzyl chloride is an important organic substance, derivatives of which are used in the pharmaceutical, cosmetic and chemical industries. You can get it in several ways, the main of which is the chlorination of toluene. This substance is toxic and causes irritation to the mucous membranes and skin, so care is required when working with it.
Description
Benzyl chloride (other names - benzyl chloride, chloromethylbenzene, alpha-chlorotulol) is an organochlorine compound derived from benzene. In the chemical industry it is used for substitution with benzyl groups in other substances. In this area is widely used.
The chemical formula of benzyl chloride is: C 6 H 5 CH 2 CI.
The structural structure of the compound is shown in the figure below.
Chemical properties
The substance has the following chemical properties:
- mixes up with organic solvents, alcohols;
- has a high reactivity;
- insoluble in water;
- the reaction of the medium is neutral;
- in the presence of certain metals (Fe, Zn, Sn, bronze, brass) - it is tarred.
Hydrolysis of benzyl chloride with its heating leads to the formation of benzyl alcohol. This process is carried out in a reactor where a 15% aqueous solution of NaβCOβ is added.
For transportation, the substance is packaged in glass or plastic containers, leaded tanks.
physical characteristics
The following properties are characteristic of benzyl chloride:
- flammability;
- density (at 25 Β° C) - 1100 kg / m 3 ;
- molar mass 126.58 g / mol;
- melting point - 234.2 K;
- boiling point - 452.5 K;
- flash point - 426.2 K;
- Vapor explosive limit - 1.1% (by volume).
The substance has a tendency to self-condensation. It is eliminated by the addition of hydrocarbons, resins and phenols.
In appearance, this compound is a colorless liquid.
Benzyl Chloride: Preparation
The main industrial method for the synthesis of this substance is the chlorination of toluene at a temperature of 90-100 Β° C. Schematic diagram of this process is shown in the figure below.
The chemistry of the reaction proceeds as follows:
The technology consists of 3 main stages:
- toluene distillation;
- its chlorination;
- separation of a multicomponent reaction product.
Ultraviolet irradiation or CβHββNβ (azobisisobutyric acid dinitrile) is used as initiators initiating radical chain processes. In the final product, the mass fraction of benzyl chloride is at least 98%. The by-products in the mixture are polychlorides (benzylidene chloride), chlorotoluene and toluene.
The formation of compounds of the first type is due to the electrophilic substitution of the hydrogen atom of the aromatic nucleus by a chlorine atom, the catalyst of which is iron chloride. An increase in the concentration of benzyl chloride in the reactor also contributes to this. For this reason, the chlorination process is not carried out to the end. The amount of starting toluene in the residue is up to 50%. In this case, the content of polychlorides does not exceed 5% by weight of benzyl chloride.
The toluene chlorination process is also greatly influenced by the purity of the reagents. So, in the presence of iron impurities, toluene is chlorinated into the core, and water vapor leads to the rapid destruction of the metal of technological equipment. The most suitable materials for reactors are silver and nickel. One of the promising ways to reduce the formation of by-products is the use of amines (dimethylamine, diethylamine, diethanolamine), which are able to bind ferric chloride to inactive complexes.
Other methods for preparing this compound are also used, as shown in the figure below.
Application
Benzyl chloride is used to produce the following materials:
- benzyl alcohol (flavoring in the food industry and perfumery, an additive in the composition of solvents, antiseptic treatment of oily drugs administered intramuscularly);
- benzyl cellulose (production of cables, paint and varnish products, βwashableβ wallpapers, pressing and injection compositions);
- benzoic acid esters (anesthetics in medicine);
- benzaldehyde (synthesis of other substances, the manufacture of dyes, perfumes and cosmetics);
- benzylamines (production of cationic dyes and drugs);
- plastics
- Quaternary ammonium salts (surfactant production).
In organic chemistry, this compound is also used to protect amino groups.
Synthesis of Derivatives
The production of benzaldehyde from benzyl chloride is carried out in several ways, which are shown in the figure below.
Benzyl alcohol is synthesized according to the technological scheme described in this figure:
This process consists of several stages:
- hydrolysis with an aqueous solution of sodium carbonate;
- allocation of crude alcohol;
- its rectification.
Benzylamines are obtained in industry by amination of liquid benzyl chloride with gaseous ammonia in an aqueous-alcoholic medium. The reactor is a standard enameled apparatus. First, a solution of alcohol is loaded, then it is saturated with ammonia. After that, the mixture is heated to 40 Β° C, benzyl chloride with nitrogen is introduced under pressure. The temperature was brought to 60 Β° C, after exposure, the mixture was sent to a collection tank, where the residues of ammonia and solvent were distilled off, which were then returned to the reactor for re-amination.
Obtaining other important derivatives occurs according to the following schemes:
- Ξ±-toluic acid C 6 H 5 CH 2 Cl + NaCN β C 6 H 5 CH 2 CN β C 6 H 5 CH 2 COOH;
- ammonium salts NR 3 + C 6 H 5 CH 2 Cl β C 6 H 5 CH 2 NR 3 + Cl - ;
- benzoic acid C 6 H 5 CH 2 Cl + 2 KOH + 2 [O] β C 6 H 5 COOK + KCl + H 2 O.
Impact on living organisms
Benzyl chloride is an explosive and fire hazardous compound. Its maximum permissible concentration in the air is 0.5 mg / m 3 . The substance has the following negative effects on the human body:
- irritation of the mucous membranes of the eyes and nose;
- spasm of the eyelids and severe lacrimation;
- the occurrence of an inflammatory process when it enters the skin;
- general toxic effects at high concentrations.
This substance is volatile enough under normal conditions. Laboratory work with its use should be carried out in a cabinet equipped with a hood. The use of personal protective equipment is also required. Benzyl chloride is capable of causing a change in hereditary properties, and is also a carcinogen.