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Tetrachlorobenzene
Tetrachlorobenzene is any of three isomeric chlorobenzenes with the molecular formula . They differ by the positions of the chlorine atoms around the ring. Tetrachlorobenzenes are colorless crystalline compounds. Properties Synthesis 1,2,4,5-Tetrachlorobenzene can be produced by electrophilic halogenation of benzenes and some chlorobenzenes. 1,2,3,4-Tetrachlorobenzene can only be produced by chlorination of 1,3,5-trichlorobenzene. Uses 1,2,4,5-tetrachlorobenzene once was used as intermediates in the production of pesicides, specifically trichlorophenols. This method has been discontinued because it also produced 2,3,7,8-tetrachlorodibenzo-p-dioxin Dioxin may refer to: * 1,2-Dioxin or 1,4-Dioxin, two unsaturated heterocyclic 6-membered rings where two carbon atoms have been replaced by oxygen atoms, giving the molecular formula C4H4O2 *Dibenzo-1,4-dioxin, the parent compound also known as .... See also * Tetrabromobenzene * Tetraiodobenzene References {{Reflist Chlor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isomeric
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Isomers do not necessarily share similar chemical or physical properties. Two main forms of isomerism are structural or constitutional isomerism, in which ''bonds'' between the atoms differ; and stereoisomerism or spatial isomerism, in which the bonds are the same but the ''relative positions'' of the atoms differ. Isomeric relationships form a hierarchy. Two chemicals might be the same constitutional isomer, but upon deeper analysis be stereoisomers of each other. Two molecules that are the same stereoisomer as each other might be in different conformational forms or be different isotopologues. The depth of analysis depends on the field of study or the chemical and physical properties of interest. The English word "isomer" () is a back-for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorobenzenes
Chlorobenzene is an aromatic organic compound with the chemical formula C6H5Cl. This colorless, flammable liquid is a common solvent and a widely used intermediate in the manufacture of other chemicals. Uses Historical The major use of chlorobenzene is as an intermediate in the production of herbicides, dyestuffs, and rubber. Chlorobenzene is also used as a high-boiling solvent in industrial applications as well as in the laboratory. Chlorobenzene is nitrated on a large scale to give a mixture of 2-nitrochlorobenzene and 4-nitrochlorobenzene, which are separated. These mononitrochlorobenzenes are converted to related 2-nitrophenol, 2-nitroanisole, bis(2-nitrophenyl)disulfide, and 2-nitroaniline by nucleophilic displacement of the chloride, with respectively sodium hydroxide, sodium methoxide, sodium disulfide, and ammonia. The conversions of the 4-nitro derivative are similar. Chlorobenzene once was used in the manufacture of pesticides, most notably DDT, by reaction with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrophilic Halogenation
In organic chemistry, an electrophilic aromatic halogenation is a type of electrophilic aromatic substitution. This organic reaction is typical of aromatic compounds and a very useful method for adding substituents to an aromatic system. : A few types of aromatic compounds, such as phenol, will react without a catalyst, but for typical benzene derivatives with less reactive substrates, a Lewis acid is required as a catalyst. Typical Lewis acid catalysts include , , and . These work by forming a highly electrophilic complex which is attacked by the benzene ring. Reaction mechanism The reaction mechanism for chlorination of benzene is the same as bromination of benzene. Iron(III) bromide and iron(III) chloride become inactivated if they react with water, including moisture in the air. Therefore, they are generated by adding iron filings to bromine or chlorine. Here is the mechanism of this reaction: : The mechanism for iodination is slightly different: iodine (I2) is treated wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline. It is used primarily as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. Although benzene is a major industrial chemical, it finds limited use in consumer items because of its toxicity. History Discovery The word "''benzene''" derives from "''gum benzoin''" (benzoin res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Espacenet
Espacenet (formerly stylized as ''esp@cenet'') is a free online service for searching patents and patent applications. Espacenet was developed by the European Patent Office (EPO) together with the member states of the European Patent Organisation. Most member states have an Espacenet service in their national language, and access to the EPO's worldwide database, most of which is in English. In 2022, the Espacenet worldwide service claimed to have records on more than 140 million patent publications. History By launching Espacenet in 1998, the EPO is said to have "revolutionized public access to international patent information, releasing patent data from its paper prisons and changing forever how patents are disseminated, organized, searched, and retrieved." In 2004, i.e. in the early years of Espacenet, Nancy Lambert considered that, although free, Espacenet, like the United States Patent and Trademark Office (USPTO) database of US patents, "still tend dto have primitive searc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1,3,5-Trichlorobenzene
1,3,5-Trichlorobenzene is an organochlorine compound. It is one of the three isomers of trichlorobenzene. Being more symmetrical than the other isomers, it exists as colourless crystals whereas the other isomers are liquids at room temperature. It is not formed upon chlorination of benzene. Instead it is prepared by the Sandmeyer reaction from 3,5-dichloroaniline Dichloroanilines are chemical compounds which consist of an aniline ring substituted with two chlorine atoms and have the molecular formula C6H5Cl2N. There are six isomers, varying in the positions of the chlorine atoms around the ring relative to .... See also * Chlorobenzenes—different numbers of chlorine substituents and isomeric forms References {{DEFAULTSORT:Trichlorobenzene, 1,3,5- Chlorobenzenes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Toxicology Program
The National Toxicology Program (NTP) is an inter-agency program run by the United States Department of Health and Human Services to coordinate, evaluate, and report on toxicology within public agencies. The National Toxicology Program is headquartered at the National Institute of Environmental Health Sciences (NIEHS). The NIEHS Director, currently Dr. Richard Woychik, Ph.D., also concurrently serves as NTP Director. History The program was established in 1978 by Joseph A. Califano Jr., then the United States Secretary of Health, Education, and Welfare (today known as the Secretary of Health and Human Services). The program arose from congressional concerns about the health effects of chemical agents in the environment. In October 1981, Secretary Richard S. Schwiker granted permanent status to the program. Interagency Center for Evaluation of Alternative Toxicological Methods The NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) supports th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dioxin
Dioxin may refer to: * 1,2-Dioxin or 1,4-Dioxin, two unsaturated heterocyclic 6-membered rings where two carbon atoms have been replaced by oxygen atoms, giving the molecular formula C4H4O2 *Dibenzo-1,4-dioxin, the parent compound also known as dibenzodioxin or dibenzo-''p''-dioxin (molecular formula C12H8O2), in which two benzene rings are connected through two oxygen atoms *Dioxins and dioxin-like compounds, a diverse range of chemical compounds which are known to exhibit "dioxin-like" toxicity *2,3,7,8-Tetrachlorodibenzodioxin (TCDD), the prototypical example of the above class, often referred to simply as "dioxin" See also * 1,4-Dioxane, the saturated analog * Agent orange, of which TCDD is a marginal component * Digoxin * Dioxin affair, a 1999 crisis in Belgium *Seveso disaster, a 1976 crisis in Italy *Times Beach, Missouri Times Beach is a ghost town in St. Louis County, Missouri, United States, southwest of St. Louis and east of Eureka. Once home to more than two t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrabromobenzene
1,2,4,5-Tetrabromobenzene is a bromobenzene with the formula C6H2Br4. It is one of three isomers of tetrabromobenzene. The compound is a white solid. 1,2,4,5-Tetrabromobenzene is an important metabolite of the flame retardant hexabromobenzene. Preparation The synthesis of 1,2,4,5-tetrabromobenzene has already been reported in 1865 from benzene and excess bromine in a sealed tube at 150 °C. However, the clearly reduced melting point of about 160 °C indicates impurities in the final product. In his 1885 dissertation, Adolf Scheufelen published the synthesis of a purer sample using iron(III) chloride FeCl as a catalyst, isolated as "pretty needles" ("schönen Nadeln"). The synthesis can also be carried out in solution in chloroform or tetrachloromethane and yields 1,2,4,5-tetrabromobenzene in 89% yield. This reaction can also be carried out in a laboratory experiment with excess bromine and iron nails (as starting material for iron (III) bromide FeBr). The inter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetraiodobenzene
Tetraiodobenzenes form a group of iodobenzenes with four iodine atoms as substituents (C6H2I4). By their different arrangement, three constitutional isomers are possible. See also *Tetrachlorobenzene *Tetrabromobenzene 1,2,4,5-Tetrabromobenzene is a bromobenzene with the formula C6H2Br4. It is one of three isomers of tetrabromobenzene. The compound is a white solid. 1,2,4,5-Tetrabromobenzene is an important metabolite of the flame retardant hexabromobenzene ... References ''Handbook of Data on Common Organic Compounds'', S. 466 (). {{cite journal , doi=10.1021/jo00172a063 , title=Periodination of benzene with periodate/Iodide , date=1983 , last1=Mattern , first1=Daniell Lewis , journal=The Journal of Organic Chemistry , volume=48 , issue=24 , pages=4772–4773 Iodobenzenes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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