In organic chemistry, an alkane, or paraffin, is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which all the carbon–carbon bonds are single. Alkanes have the general chemical formula CnH2n+2. The alkanes range in complexity from the simplest case of methane, where n = 1, to arbitrarily large and complex molecules, like pentacontane or 6-ethyl-2-methyl-5-(1-methylethyl) octane, an isomer of tetradecane.
In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or in the terminal position. Terminal alkenes are also known as α-olefins.
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula CnH2n−2. Alkynes are traditionally known as acetylenes, although the name acetylene also refers specifically to C2H2, known formally as ethyne using IUPAC nomenclature. Like other hydrocarbons, alkynes are generally hydrophobic.
Bromine is a chemical element; it has symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between those of chlorine and iodine. Isolated independently by two chemists, Carl Jacob Löwig and Antoine Jérôme Balard, its name was derived from the Ancient Greek βρῶμος (bromos) meaning "stench", referring to its sharp and pungent smell.
The haloalkanes are alkanes containing one or more halogen substituents. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially. They are used as flame retardants, fire extinguishants, refrigerants, propellants, solvents, and pharmaceuticals. Subsequent to the widespread use in commerce, many halocarbons have also been shown to be serious pollutants and toxins. For example, the chlorofluorocarbons have been shown to lead to ozone depletion. Methyl bromide is a controversial fumigant. Only haloalkanes that contain chlorine, bromine, and iodine are a threat to the ozone layer, but fluorinated volatile haloalkanes in theory may have activity as greenhouse gases. Methyl iodide, a naturally occurring substance, however, does not have ozone-depleting properties and the United States Environmental Protection Agency has designated the compound a non-ozone layer depleter. For more information, see Halomethane. Haloalkane or alkyl halides are the compounds which have the general formula "RX" where R is an alkyl or substituted alkyl group and X is a halogen.
In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. This kind of conversion is in fact so common that a comprehensive overview is challenging. This article mainly deals with halogenation using elemental halogens. Halides are also commonly introduced using salts of the halides and halogen acids. Many specialized reagents exist for and introducing halogens into diverse substrates, e.g. thionyl chloride.
In organic chemistry, an aryl halide is an aromatic compound in which one or more hydrogen atoms, directly bonded to an aromatic ring are replaced by a halide. The haloarene are different from haloalkanes because they exhibit many differences in methods of preparation and properties. The most important members are the aryl chlorides, but the class of compounds is so broad that there are many derivatives and applications.
In organic chemistry, free-radical addition is an addition reaction which involves free radicals. Radical additions are known for a variety of unsaturated substrates, both olefinic or aromatic and with or without heteroatoms.
Halomethane compounds are derivatives of methane with one or more of the hydrogen atoms replaced with halogen atoms. Halomethanes are both naturally occurring, especially in marine environments, and human-made, most notably as refrigerants, solvents, propellants, and fumigants. Many, including the chlorofluorocarbons, have attracted wide attention because they become active when exposed to ultraviolet light found at high altitudes and destroy the Earth's protective ozone layer.
Organochlorine chemistry is concerned with the properties of organochlorine compounds, or organochlorides, organic compounds containing at least one covalently bonded atom of chlorine. The chloroalkane class includes common examples. The wide structural variety and divergent chemical properties of organochlorides lead to a broad range of names, applications, and properties. Organochlorine compounds have wide use in many applications, though some are of profound environmental concern, with TCDD being one of the most notorious.
In organic chemistry, α-keto halogenation is a special type of halogenation. The reaction may be carried out under either acidic or basic conditions in an aqueous medium with the corresponding elemental halogen. In this way, chloride, bromide, and iodide functionality can be inserted selectively in the alpha position of a ketone.
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.
The Hunsdiecker reaction is a name reaction in organic chemistry whereby silver salts of carboxylic acids react with a halogen to produce an organic halide. It is an example of both a decarboxylation and a halogenation reaction as the product has one fewer carbon atoms than the starting material and a halogen atom is introduced its place. A catalytic approach has been developed.
A halonium ion is any onium ion containing a halogen atom carrying a positive charge. This cation has the general structure R−+X−R′ where X is any halogen and no restrictions on R, this structure can be cyclic or an open chain molecular structure. Halonium ions formed from fluorine, chlorine, bromine, and iodine are called fluoronium, chloronium, bromonium, and iodonium, respectively. The 3-membered cyclic variety commonly proposed as intermediates in electrophilic halogenation may be called haliranium ions, using the Hantzsch-Widman nomenclature system.
Iodine compounds are compounds containing the element iodine. Iodine can form compounds using multiple oxidation states. Iodine is quite reactive, but it is much less reactive than the other halogens. For example, while chlorine gas will halogenate carbon monoxide, nitric oxide, and sulfur dioxide, iodine will not do so. Furthermore, iodination of metals tends to result in lower oxidation states than chlorination or bromination; for example, rhenium metal reacts with chlorine to form rhenium hexachloride, but with bromine it forms only rhenium pentabromide and iodine can achieve only rhenium tetraiodide. By the same token, however, since iodine has the lowest ionisation energy among the halogens and is the most easily oxidised of them, it has a more significant cationic chemistry and its higher oxidation states are rather more stable than those of bromine and chlorine, for example in iodine heptafluoride.
In chemistry, a reaction intermediate, or intermediate, is a molecular entity arising within the sequence of a stepwise chemical reaction. It is formed as the reaction product of an elementary step, from the reactants and/or preceding intermediates, but is consumed in a later step. It does not appear in the chemical equation for the overall reaction.
In chemistry, the haloform reaction is a chemical reaction in which a haloform is produced by the exhaustive halogenation of an acetyl group, in the presence of a base. The reaction can be used to transform acetyl groups into carboxyl groups or to produce chloroform, bromoform, or iodoform. Note that fluoroform can't be prepared in this way.
Organobromine chemistry is the study of the synthesis and properties of organobromine compounds, also called organobromides, which are organic compounds that contain carbon bonded to bromine. The most pervasive is the naturally produced bromomethane.
Radical disproportionation encompasses a group of reactions in organic chemistry in which two radicals react to form two different non-radical products. Radicals in chemistry are defined as reactive atoms or molecules that contain an unpaired electron or electrons in an open shell. The unpaired electrons can cause radicals to be unstable and reactive. Reactions in radical chemistry can generate both radical and non-radical products. Radical disproportionation reactions can occur with many radicals in solution and in the gas phase. Due to the reactive nature of radical molecules, disproportionation proceeds rapidly and requires little to no activation energy. The most thoroughly studied radical disproportionation reactions have been conducted with alkyl radicals, but there are many organic molecules that can exhibit more complex, multi-step disproportionation reactions.
Photochlorination is a chlorination reaction that is initiated by light. Usually a C-H bond is converted to a C-Cl bond. Photochlorination is carried out on an industrial scale. The process is exothermic and proceeds as a chain reaction initiated by the homolytic cleavage of molecular chlorine into chlorine radicals by ultraviolet radiation. Many chlorinated solvents are produced in this way.
