1,4-Dichlorobenzene
Encyclopedia
1,4-Dichlorobenzene is an organic compound
with the formula
C6H4Cl2. This colorless solid
has a strong odor
. It consists of two chlorine
atoms substituted at opposing sites on a benzene
ring. p-DCB is used a pesticide and a deodorant, most familiarly in mothball
s in which it is a replacement for the more traditional naphthalene
. p-DCB is also used as a precursor in the production of the polymer poly(p-phenylene sulfide)
.
of benzene using ferric chloride as a catalyst:
The chief impurity is the 1,2 isomer. The compound can be purified by fractional crystallisation, taking advantage of its relatively high melting point of 53.5 °C; the isomeric dichlorobenzene
s and chlorobenzene melt well below room temperature.
s, moulds, and mildew
. It finds use as a disinfectant in waste containers and restrooms and is the characteristic smell associated with urinal cakes. Its usefulness in these arises from p-DCB's low solubility in water and its relatively high volatility: it sublimes readily near room temperature.
with hydroxyl, amine, and sulfide groups. In a growing application, p-DCB is the precursor to the high performance polymer poly(p-phenylene sulfide)
:
(IARC) have determined that p-DCB may reasonably be anticipated to be a carcinogen
, although there is no direct evidence. Animals given very high levels in water developed liver
and kidney
tumor
s . The United States Environmental Protection Agency
(EPA) has set a target maximum contaminant level of 75 micrograms of p-DCB per liter of drinking water
(75 μg/L). p-DCB is also an EPA-registered pesticide. The US Occupational Safety and Health Administration
(OSHA) has set a maximum level of 75 parts of p-DCB per million parts air in the workplace (75 ppm) for an 8-hour day, 40-hour workweek
.
Little information is available on how children react to p-DCB exposure; however, consumption of p-DCB can cause vomiting in adults. A 2010 Japanese study found that the compound has anabolic-androgenic effect in rats and reduces sperm production although it does not bind to the androgen receptor
, and neither does its major metabolite
, 2,5-dichlorophenol.
Under California's Proposition 65, p-DCB is listed as "known to the State to cause cancer".
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
C6H4Cl2. This colorless solid
Solid
Solid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...
has a strong odor
Odor
An odor or odour is caused by one or more volatilized chemical compounds, generally at a very low concentration, that humans or other animals perceive by the sense of olfaction. Odors are also commonly called scents, which can refer to both pleasant and unpleasant odors...
. It consists of two chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
atoms substituted at opposing sites on a benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
ring. p-DCB is used a pesticide and a deodorant, most familiarly in mothball
Mothball
Mothballs are small balls of chemical pesticide and deodorant used when storing clothing and other articles susceptible to damage from mold or moth larvae ....
s in which it is a replacement for the more traditional naphthalene
Naphthalene
Naphthalene is an organic compound with formula . It is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings...
. p-DCB is also used as a precursor in the production of the polymer poly(p-phenylene sulfide)
Poly(p-phenylene sulfide)
Polyphenylene sulfide is an organic polymer consisting of aromatic rings linked with sulfides. Synthetic fiber and textiles derived from this polymer are known to resist chemical and thermal attack. PPS is used to make filter fabric for coal boilers, papermaking felts, electrical insulation,...
.
Production
p-DCB is produced by chlorinationChlorination
Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water...
of benzene using ferric chloride as a catalyst:
- C6H6 + 2 Cl2 → C6H4Cl2 + 2 HClHydrogen chlorideThe compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...
The chief impurity is the 1,2 isomer. The compound can be purified by fractional crystallisation, taking advantage of its relatively high melting point of 53.5 °C; the isomeric dichlorobenzene
Dichlorobenzene
There are three distinct chemical compounds which are dichlorobenzenes:*1,2-Dichlorobenzene or ortho-dichlorobenzene;*1,3-Dichlorobenzene or meta-dichlorobenzene;*1,4-Dichlorobenzene or para-dichlorobenzene....
s and chlorobenzene melt well below room temperature.
Disinfectant, deodorant, and pesticide
p-DCB is used to control mothMoth
A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...
s, moulds, and mildew
Mildew
Mildew refers to certain kinds of molds or fungi.In Old English, it meant honeydew , and later came to mean mildew in the modern sense of mold or fungus....
. It finds use as a disinfectant in waste containers and restrooms and is the characteristic smell associated with urinal cakes. Its usefulness in these arises from p-DCB's low solubility in water and its relatively high volatility: it sublimes readily near room temperature.
Precursor to other chemicals
The chlorides on p-DCB can be substitutedNucleophilic substitution
In organic and inorganic chemistry, nucleophilic substitution is a fundamental class of reactions in which an electron nucleophile selectively bonds with or attacks the positive or partially positive charge of an atom or a group of atoms called the leaving group; the positive or partially positive...
with hydroxyl, amine, and sulfide groups. In a growing application, p-DCB is the precursor to the high performance polymer poly(p-phenylene sulfide)
Poly(p-phenylene sulfide)
Polyphenylene sulfide is an organic polymer consisting of aromatic rings linked with sulfides. Synthetic fiber and textiles derived from this polymer are known to resist chemical and thermal attack. PPS is used to make filter fabric for coal boilers, papermaking felts, electrical insulation,...
:
Environmental effects
p-DCB is poorly soluble in water and is not easily broken down by soil organisms. Like many hydrocarbons, p-DCB is lipophilic and will accumulate in the fatty tissues.Health effects
The US Department of Health and Human Services (DHHS) and the International Agency for Research on CancerInternational Agency for Research on Cancer
The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....
(IARC) have determined that p-DCB may reasonably be anticipated to be a carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
, although there is no direct evidence. Animals given very high levels in water developed liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
and kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s . The United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
(EPA) has set a target maximum contaminant level of 75 micrograms of p-DCB per liter of drinking water
Drinking water
Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...
(75 μg/L). p-DCB is also an EPA-registered pesticide. The US Occupational Safety and Health Administration
Occupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...
(OSHA) has set a maximum level of 75 parts of p-DCB per million parts air in the workplace (75 ppm) for an 8-hour day, 40-hour workweek
Workweek
The workweek and weekend are those complementary parts of the week devoted to labour and rest respectively. The legal working week , or workweek , is the part of the seven-day week devoted to labor. In most Western countries it is Monday to Friday. The weekend comprises the two traditionally...
.
Little information is available on how children react to p-DCB exposure; however, consumption of p-DCB can cause vomiting in adults. A 2010 Japanese study found that the compound has anabolic-androgenic effect in rats and reduces sperm production although it does not bind to the androgen receptor
Androgen receptor
The androgen receptor , also known as NR3C4 , is a type of nuclear receptor that is activated by binding of either of the androgenic hormones testosterone or dihydrotestosterone in the cytoplasm and then translocating into the nucleus...
, and neither does its major metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...
, 2,5-dichlorophenol.
Under California's Proposition 65, p-DCB is listed as "known to the State to cause cancer".
External links
- Mothball sniffing warning issued, BBC News, 27 July 2006