Industrial-grade 99.9% 1,4-Dichlorobenzene CAS 106-46-7

What is 1,4-Dichlorobenzene? How does it work?

1,4-Dichlorobenzene, also known as para-dichlorobenzene (or p-Dichlorobenzene, PDCB, para-DCB), is the para-isomer of dichlorobenzene, a white crystalline solid with a strong camphor odor. It is the main ingredient of mothballs and a monomer for the production of polyphenylene sulphide (PPS), a high performance engineering plastic. 1,4-Dichlorobenzene is used in everyday hygiene products and high-end new materials, from wardrobe mothproofing to automotive parts.

Identification data: Molecular formula C6H4Cl2 , molecular weight 147.00 , CAS number 106-46-7 , EC number 203-400-5 , UN 3077 (hazardous to the environment).

Physically, p-dichlorobenzene is a colourless to white crystalline solid with a strong camphor odour; it has a density of 1.25 g/cm³; a melting point of 53.5℃ (higher than the ortho/meta isomer, which is the basis of stepwise crystallisation purification); a boiling point of 174℃; extremely low water solubility (approx. 10.5 mg/100 mL at 20℃); and relatively high vapour pressure (1.3 mmHg at 20℃), subliming at room temperature, which are its key physical properties as a moth fumigant.

Chemically, p-dichlorobenzene is an aromatic chlorinated hydrocarbon: the two chlorine atoms are in the para position, giving the aromatic ring a specific substitution directing effect (nitration mainly produces 2,5-dichloronitrobenzene/1,4-dichloro-2-nitrobenzene); the chlorine sites can be replaced by nucleophilic groups (sulfides, hydroxylamines, etc.) (condensing with sodium sulfide to form PPS); it has a flash point of 66℃ and a lower explosive limit of 2.5%, making it a flammable solid; it is highly lipophilic and can accumulate in biological adipose tissue. It must be stored in a sealed container, away from fire and oxidizers.

From the perspective of mechanism of action, industrial-grade p-dichlorobenzene plays an irreplaceable role due to its "easy sublimation and volatility + the activity of aromatic chlorine". The mechanism of action in different applications is as follows:

1.Sublimation and volatilization mechanism (slow-release fumigation)

p-Dichlorobenzene has a high vapor pressure and can sublimate at room temperature. The solid slowly vaporizes and forms a stable concentration of vapor in enclosed spaces (wardrobes, bathrooms, warehouses). This is the core physical basis for its use as a fumigant for preventing moths, mildew, and deodorizing—slow volatilization and long-lasting effect.

2.Insecticidal and antifungal toxicological mechanism (volatile toxicity)

Vapour of p-Dichlorobenzene is toxic and repellent to clothes moth larvae, woodworms and mould. It has low water solubility and is hard to wash off with water. It has high lipophilicity and easily penetrates the cuticle of pests and creates a protective atmosphere around clothing and collectibles.

3.Polycondensation reaction mechanism (PPS synthesis)

The polycondensation of p-dichlorobenzene with sodium sulphide (Na 2 S) in the polar solvent can proceed by nucleophilic substitution of both para-chlorine atoms. The chlorine is replaced by sulphide anions and then connected to form segments of p-phenylene sulphide, resulting in polyphenylene sulphide (PPS) engineering plastics with high-temperature and corrosion resistance.

4.Aromatic ring substitution reaction mechanism (synthesis of dye intermediates)

The para-directing effect of the two chlorine atoms on the aromatic ring of dichlorobenzene causes its nitration to mainly produce 2,5-dichloronitrobenzene (1,4-dichloro-2-nitrobenzene). The latter can be further reduced and substituted to prepare a series of dye and pigment intermediates. The orientation and leaving ability of the chlorine atoms determine the synthetic route.

5.Lipophilic permeation mechanism (basic bioactivity)

p-Dichlorobenzene has a strong lipophilicity and can easily dissolve and penetrate into lipid-soluble matrices (insect epidermis, organic materials). This is the basis for its insecticidal activity and material penetration application, and also the reason why it easily accumulates in biological adipose tissue and needs to be strictly controlled.

To summarise, p-dichlorobenzene is an industrial chemical used in a wide variety of applications ranging from mothballs to engineering plastics. It has a wide range of application, from everyday hygiene to high-end industrial products, due to its sublimation volatilisation and aromatic chlorine activity, including mothproofing clothing, deodorising toilets, PPS new materials and dye intermediates.

What are the applications of industrial-grade 1,4-Dichlorobenzene?

1.Moth and mildew repellents and mothballs (core application in daily hygiene products)

Application Field: Daily Hygiene & Clothing Care

Corresponding Products: Mothballs, mothproof sheets/bags, drawer repellents, mothproof and mildew-proof agents for fur and silk collectibles, moisture-proof & mildew-proof blocks

Applicability Principle: p-Dichlorobenzene sublimates at room temperature to generate stable fumigation vapours, which are toxic and repellent to clothes moths and woodworms and inhibit mould growth. Its extremely low water solubility prevents it from being washed away by moisture. It sustains long-term mothproof and mildew-proof performance inside sealed wardrobes and serves as a safer alternative to traditional naphthalene mothballs (naphthalene has higher flammability).

2.Deodorizing and disinfecting agents (core application in environmental sanitation)

Application Field: Environmental Sanitation & Public Facilities

Corresponding Products: Urinal cakes, toilet deodorizing blocks, disinfectant & deodorizer for garbage containers, fumigation disinfection tablets for public toilets, sewer deodorizers

Applicability Principle: p-Dichlorobenzene readily sublimes and continuously releases vapours to mask and suppress odours (its characteristic odour is commonly associated with public toilets). It also delivers moderate disinfection activity against environmental microorganisms. Low water solubility allows slow dissolution and sustained vapour release in humid environments such as urinals and garbage cans, providing a low-cost and long-lasting deodorisation & disinfection solution.

3.Monomer for the synthesis of polyphenylene sulfide (PPS) (core application in the field of new materials)

Application Field: High-performance Engineering Plastics & New Materials

Corresponding Products: Polyphenylene sulfide (PPS) resin and modified materials, PPS automotive parts (engine peripherals, cooling systems), electronic connectors and relays, heat-resistant home appliance components, chemical pumps, valves and seals, PPS fibres and films

Applicability Principle: Polyphenylene sulfide is formed by the condensation polymerization, where the two para-chlorine atoms of p-dichlorobenzene react with sodium sulfide. PPS possesses excellent high-temperature resistance (long-term resistance above 200℃), chemical corrosion resistance, flame retardancy, dimensional stability, and electrical insulation properties, making it an important specialty engineering plastic in the automotive, electronics, and chemical industries. p-Dichlorobenzene is an irreplaceable synthetic monomer for PPS.

4.Dye and pigment intermediates (dye industry sector)

Application Field: Dyes and Pigments Industry

Corresponding Products: 1,4-Dichloro-2-nitrobenzene (2,5-dichloronitrobenzene) intermediates, azo dye & pigment intermediates, disperse dyes, organic pigments

Applicability Principle: The nitration of p-dichlorobenzene yields dichloronitrobenzene due to substituent directing effects and chlorine reactivity, making it a critical precursor for azo dyes and pigments. Reactions such as nitro reduction and chlorine substitution introduce chromophores and auxochromes. These intermediates are widely used in manufacturing textile dyes and plastic pigments.

5.Fine chemical synthesis intermediates (fine chemical industry)

Application Field: Fine Chemicals & Organic Synthesis

Corresponding Products: 2,5-Dichloroaniline, p-chlorobenzenethiophenol, aryl sulfides/aryl hydroxylamine derivatives, specialty aromatic compounds

Applicability Principle: The two chlorine sites of p-dichlorobenzene can undergo nucleophilic substitution by sulfides, hydroxylamines and other groups to form aromatic sulfur- and nitrogen-containing intermediates. These intermediates are used to synthesise fine chemicals including pesticides and dyestuffs, and are fundamental raw materials for aromatic fine chemicals.

6.Chemical analysis reagents and laboratory standards (scientific research field)

Application Field: Scientific Research & Testing Analysis

Corresponding Products: Analytical-grade/high-purity p-dichlorobenzene reagents, solvents for organic synthesis and recrystallisation media, chromatographic standards, environmental monitoring reference substances

Applicability Principle: p-Dichlorobenzene has a high melting point, can be readily purified via stepwise crystallisation and exhibits good stability. It is a commonly utilised reagent and reference material for laboratory organic synthesis, recrystallisation purification, and environmental monitoring (detection of dichlorobenzene pollutants in drinking water, air and soil).

To summarise, industrial grade p-dichlorobenzene (C6H4Cl2, CAS 106-46-7) is a versatile chemical that can be used in mothballs and engineering plastics. It uses sublimation, volatilisation, fumigation, and aromatic chlorine activity, and has a mature application in seven major industries, including mothballs, deodorising disinfectants, polyphenylene sulphide (PPS) synthesis monomers, dye and pigment intermediates, fine chemical intermediates, and analytical reagents. Of high-end new materials, the application of PPS synthesis is the fastest growing in the area.