Chlorobenzophenone: Properties, Applications, Synthesis, and Safety Considerations
4-Chlorobenzophenone, also known as p-Chlorobenzophenone, is a chemical compound with the molecular formula C13H9ClO. It belongs to the class of aromatic ketones and is used in various industrial applications, including as an intermediate in organic synthesis.
- Chemical Properties
Molecular Formula: C13H9ClO
Molecular Weight: 216.66 g/mol
CAS Number: 134-85-0
Appearance: The compound is a white to off-white crystalline powder.
Melting Point: 74-77°C
Boiling Point: 324°C
Solubility: The compound is slightly soluble in water and soluble in organic solvents such as ethanol, methanol, and acetone.
- Application
- Pharmaceutical Industry
- a) Drug synthesis:
It plays a pivotal role in the synthesis of an array of pharmaceutical compounds.
It is employed in the manufacture of certain antidepressant medications, particularly those belonging to the selective serotonin reuptake inhibitor (SSRI) category.
It is involved in the synthesis of certain antipsychotic medications.
It is employed in the synthesis of specific antihistamines and anti-inflammatory drugs.
- b) Active Pharmaceutical Ingredients (APIs):
In certain instances, derivatives of 4-chlorobenzophenone are employed as active pharmaceutical ingredients (APIs) without further modification.
- Agrochemical Industry
4-Chlorobenzophenone is utilised in the manufacture of agrochemicals, including:
Herbicides:
It functions as an intermediate in the synthesis of herbicidal compounds, which are employed for the control of unwanted vegetation in agricultural fields.
Pesticides:
It is employed in the creation of pesticide formulations that safeguard crops from pests and diseases, thereby enhancing agricultural productivity.
- Material Science
Polymer and Materials Science:
- a) Photoinitiators:
It functions as a photoinitiator in UV-curable coatings and inks.
Upon exposure to UV light, the initiator initiates polymerisation reactions, thereby enabling the rapid curing of materials.
- b) Polymer additives:
Used as a stabilising agent in specific polymer formulations to improve their resistance to degradation by ultraviolet light.
- Chemical Industry
The synthesis of fine chemicals is a process whereby chemical compounds are created for use in a variety of applications.
It functions as an intermediate in the production of fine chemicals, which are utilized in a multitude of applications, including the synthesis of dyes, pigments, and perfumes.
Cross-coupling reactions represent a significant area of research within the field of organic chemistry.
These are employed in cross-coupling reactions, including the Suzuki and Heck reactions, which are fundamental to the construction of complex organic molecules.
- Cosmetics and Personal Care
The function of UV absorbers is to absorb ultraviolet radiation, thereby protecting the integrity of a product and the skin.
The utilisation of this compound in formulations that require UV protection is predicated upon its capacity to absorb UV radiation, thereby safeguarding the integrity of the product and the skin.
- Dye and Pigment Industry:
It functions as an intermediary in the synthesis of specific dyes, particularly those utilized in textile and printing ink production.
It is involved in the synthesis of photochromic dyes, which undergo a change in colour when exposed to light.
- Fragrance Industry:
Although not employed as a fragrance in and of itself, it functions as a precursor in the synthesis of specific fragrance compounds.
- Electronics Industry:
The production of photoresists is a key step in the manufacture of printed circuit boards and semiconductor devices.
- Synthesis
- Method 1
The reactants are as follows:
Chlorobenzene (C6H5Cl) is the source of the aromatic ring.
Benzoyl chloride (C6H5COCl) furnishes the acyl group.
Aluminium chloride (AlCl3) functions as a Lewis acid catalyst.
Procedure:
Prior to commencing the experiment, the following preparatory steps must be undertaken:
It is necessary to equip a reaction flask with a stirring mechanism and a cooling bath.
It is imperative to ascertain that the flask is free from moisture, as the presence of water can result in the deactivation of the catalyst.
The addition of the catalyst should be carried out in accordance with the relevant safety protocols.
A stoichiometric quantity of aluminium chloride should then be added to the reaction flask. It is typical to utilise a slight excess of AlCl₃ in order to ensure a complete reaction.
The reaction is as follows:
Benzoyl chloride should be added to the flask containing AlCl3 at a slow rate, while maintaining low temperatures (0-5°C), in order to control the exothermic nature of the reaction.
The addition of chlorobenzene to the mixture should be carried out gradually, with continuous stirring.
The reaction should be allowed to proceed, with the temperature gradually increased to room temperature and then to reflux (approximately 80-90°C) in order to complete the reaction.
The procedure for quenching and work-up is as follows:
Once the reaction has reached completion, the mixture should be quenched with ice-cold water in order to decompose the aluminium complex.
The organic layer should then be extracted with an organic solvent, such as diethyl ether or dichloromethane.
The organic layer should then be washed with water, diluted hydrochloric acid and a sodium bicarbonate solution in order to remove any residual catalyst and acidic impurities.
The organic layer should then be dried over anhydrous sodium sulfate.
The subsequent stage is purification.
The organic layer should then be concentrated by evaporation under reduced pressure.
The crude product should then be purified by recrystallisation from an appropriate solvent, which is typically ethanol or methanol. This will result in the production of pure 4-chlorobenzophenone.
- Method 2
The process of acylation utilises acyl anhydrides.
In certain instances, this method may provide conditions that are less severe and greater selectivity.
The utilisation of catalysts is a crucial aspect of the aforementioned method. There are, however, a number of variations in the catalysts themselves that may be employed.
The utilisation of disparate Lewis acids or the deployment of reusable solid acid catalysts, such as zeolites or polymer-supported catalysts, can confer environmental and economic advantages.
- Safety and Handling
It is recommended that 4-chlorobenzophenone be handled with caution, given the potential health risks associated with its use. Contact with the substance may result in irritation to the skin and eyes. It is imperative that the appropriate personal protective equipment (PPE) is worn when handling this compound, including gloves, safety glasses and lab coats. It is recommended that the substance be stored in a cool, dry environment, away from sources of ignition and materials with which it is incompatible.
