In chemistry Chemistry is the science of matter and the changes it undergoes. The science of matter is also addressed by physics, but while physics takes a more general and fundamental approach, chemistry is more specialized, being concerned with the composition, behavior, structure, and properties of matter, as well as the changes it undergoes during chemical, an alkyl group is an alkane Alkanes are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i.e., hydrocarbons), wherein these atoms are linked together exclusively by single bonds (i.e., they are saturated compounds). Alkanes belong to a homologous series of organic compounds in which the members differ by a constant relative molecular mass of 1 missing one hydrogen Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of 1.00794 u (1.007825 u for Hydrogen-1), hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its. It has the general formula CnH2n+1. Typically an alkyl is a part of a larger molecule. In structural formulae The structural formula of a chemical compound is a graphical representation of the molecular structure, showing how the atoms are arranged. The chemical bonding within the molecule is also shown, either explicitly or implicitly. There are three common representations used in publications: text, Lewis type and line-angle formula. Also several other, the symbol R is used to designate a generic (unspecified) alkyl group. The smallest alkyl group is methyl In chemistry, a methyl group is a hydrophobic alkyl functional group named after methylene (RC , with the formula CH3—. [1]
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Alkyls in everyday life
The word root alkyl is encountered in several contexts in everyday life. Alkylation Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in organic molecules. Many biological target molecules is an important operation in refineries, for example in the production of high-octane gasoline. Alkylating antineoplastic agents An alkylating antineoplastic agent is an alkylating agent used in cancer treatment that attaches an alkyl group to DNA refer to a class of compounds that are used to treat cancer. In such case, the term alkyl is used loosely. For example, nitrogen mustards The nitrogen mustards are cytotoxic chemotherapy agents similar to mustard gas. Although their common use is medicinal, in principle these compounds can also be deployed as chemical warfare agents. Nitrogen mustards are nonspecific DNA alkylating agents. Nitrogen mustard gas was stockpiled by several nations during the Second World War, but it was are well-known alkylating agents, but they are more complex than a mere hydrocarbon. In chemistry, alkyl refers to a group, a substituent, that is attached to other molecular fragments. For example, alkyl lithium reagents An organolithium reagent is an organometallic compound with a direct bond between a carbon and a lithium atom. As the electropositive nature of lithium puts most of the charge density of the bond on the carbon atom, effectively creating a carbanion, organolithium compounds are extremely powerful bases and nucleophiles have the empirical formula Li(alkyl), where alkyl = methyl, ethyl, etc. A dialkyl ether is an ether Ether is a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether" . Ethers are common in organic chemistry and pervasive in biochemistry, as they with two alkyl groups, e.g., diethyl ether (O(C2H5)2).
Alkyl cations, anions, and radicals
Usually alkyl groups are attached to other atoms or groups of atoms. Free alkyls occur as neutral compounds, as anions, or as cations. The neutral alkyls are called free radicals In chemistry, radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. The unpaired electrons cause them to be highly chemically reactive. Radicals play an important role in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes, including human. The cations are called carbocations A carbocation is an ion with a positively-charged carbon atom. The charged carbon atom in a carbocation is a "sextet", i.e. it has only six electrons in its outer valence shell instead of the eight valence electrons that ensures maximum stability (octet rule). Therefore carbocations are often reactive, seeking to fill the octet of. The anions are called carbanions A carbanion is an anion in which carbon has an unshared pair of electrons and bears a negative charge usually with three substituents for a total of eight valence electrons . The carbanion exists in a trigonal pyramidal geometry. Formally a carbanion is the conjugate base of a carbon acid. Such species are usually encountered only as transient intermediates, but some are quite stable and can be "put into a bottle." Typically alkyl cations are generated using super acids A superacid is an acid with an acidity greater than that of 100% pure sulfuric acid, which has a Hammett acidity function of −12. Commercially available superacids include trifluoromethanesulfonic acid (CF3SO3H), also known as triflic acid, and fluorosulfonic acid (FSO3H), both of which are about a thousand times stronger (i.e. have more, alkyl anions are observed in the presence of strong bases, and alkyl radicals are generated by a photochemical reaction Photochemistry, a sub-discipline of chemistry, is the study of the interactions between light and atoms or molecules. Photochemistry describes chemical reactions that proceeds with the absorption of light. Everyday examples include the degradation of plastics and the formation of vitamin D in sunlight. Alkyls are commonly observed in mass spectrometry Mass spectrometry is an analytical technique for the determination of the elemental composition of a sample or molecule. It is also used for elucidating the chemical structures of molecules, such as peptides and other chemical compounds. The MS principle consists of ionizing chemical compounds to generate charged molecules or molecule fragments of organic compounds An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic. The distinction between "organic" and ".
Nomenclature
Alkyls form homologous series In chemistry, a homologous series is a series of organic compounds with a similar general formula, possessing similar chemical properties due to the presence of the same functional group, and shows a gradation in physical properties as a result of increase in molecular size and mass . For example, ethane has a higher boiling point than methane. The simplest series have the general formula CnH2n+1. Alkyls include methyl In chemistry, a methyl group is a hydrophobic alkyl functional group named after methylene (RC , CH3· (named after methane Methane is a chemical compound with the chemical formula CH4. It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees. Burning methane in the presence of oxygen produces carbon dioxide and water. The relative abundance of methane makes it an attractive fuel. However, because it is a gas at), ethyl In chemistry, an ethyl group is an alkyl functional group derived from ethane . It has the formula -C2H5 and is very often abbreviated -Et (C2H5·), propyl In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula -C3H7. It is the substituent form of the alkane propane (C3H7·), butyl In organic chemistry, butyl is a four-carbon alkyl radical or substituent group with general chemical formula -C4H9, derived from either of the two isomers of butane (C4H9·), pentyl In organic chemistry, pentyl is a five-carbon alkyl substituent with chemical formula -C5H11. It is the substituent form of the alkane pentane. In older literature, the common non-systematic name "amyl" was often used for the pentyl group (C5H11·), and so on. Alkyl groups that contain one ring have the formula CnH2n-1, e.g. cyclopropyl and cyclohexyl. The naming convention is taken from IUPAC nomenclature IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. It is developed and kept up to date under the auspices of the International Union of Pure and Applied Chemistry . The rules for naming organic and inorganic compounds are contained in two publications, known as the Blue Book and the:
These names are used to name branched chained structures, for example 3-methylpentane:
The structure of 3-methylpentane is viewed as consisting of two parts. First, five atoms comprise the longest straight chain of carbon Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of centers. The parent five-carbon compound is named pentane (highlighted blue). The methyl "substituent" or "group" is highlighted red. According the usual rules of nomenclature, alkyl groups are included in the name of the molecule before the root, as in methylpentane. This name is, however, ambiguous, as the methyl branch could be on various carbon atoms. Thus, the name is 3-methylpentane 3-Methylpentane is a branched-chain alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the third carbon atom in a pentane chain. It is of similar structure to the isomeric 2-methylpentane, which has the methyl group located on the second carbon of the pentane chain to avoid ambiguity: The 3- is because the methyl is attached to the third of the 5-carbon atoms.
If there is more than one of the same alkyl group attached to a chain, then the prefixes are used on the alkyl groups to indicate multiples (i.e., di, tri, tetra, etc.)
This compound is known as 2,3,3-trimethylpentane. Here, there are three identical alkyl groups attached to carbon atoms 2, 3, and 3. These numbers are included in the name to avoid ambiguity on the position of the groups, and 'tri' indicates that there are three identical methyl groups. If one of the methyl attached to the third carbon atom were an ethyl group, then the name would become 3-ethyl-2,3-dimethylpentane. Note that, when there are different alkyl groups, they are listed in alphabetical order.
See also
- Alkane Alkanes are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i.e., hydrocarbons), wherein these atoms are linked together exclusively by single bonds (i.e., they are saturated compounds). Alkanes belong to a homologous series of organic compounds in which the members differ by a constant relative molecular mass of 1
- Alkene In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond. The simplest acyclic alkenes, with only one double bond and no other functional groups, form an homologous series of hydrocarbons with the general formula CnH2n
- Alkyne Alkynes are hydrocarbons that have a triple bond between two carbon atoms, with the 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 but tend to be more reactive
- Aryl In the context of organic molecules, aryl refers to any functional group or substituent derived from a simple aromatic ring, be it phenyl, thiophene, indolyl, etc . "Aryl" is used for the sake of abbreviation or generalization
- Hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls. Aromatic hydrocarbons , alkanes, alkenes, cycloalkanes and alkyne-based compounds are different types of hydrocarbons
- IUPAC nomenclature of organic chemistry The IUPAC nomenclature of organic chemistry is a systematic method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry . Ideally, every organic compound should have a name from which an unambiguous structural formula can be drawn. There is also an IUPAC nomenclature of inorganic chemistry
References
- ^ Virtual Textbook of Organic Chemistry Naming Organic Compounds
Categories: Functional groups
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