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, a methyl group is a hydrophobic In chemistry, hydrophobicity is the physical property of a molecule (known as a hydrophobe) that is repelled from a mass of water alkyl In chemistry, an alkyl group is an alkane missing one hydrogen. It has the general formula CnH2n+1. Typically an alkyl is a part of a larger molecule. In structural formulae, the symbol R is used to designate a generic alkyl group. The smallest alkyl group is methyl, with the formula CH3— functional group In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of. However, its relative reactivity can be named after methylene Methylene groups in a chain or ring contribute to its size and lipophilicity. Methylene was also the old original name for methanol (RC 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 H 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 its2R or C 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 H 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 its3O Oxygen (pronounced /ˈɒksɨdʒɨn/, OK-si-jin, from the Greek roots ὀξύς (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter), is the element with atomic number 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly H 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 formula A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound -C 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 H 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 its3 and is often abbreviated -Me. Such 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 groups occur in many 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 ".
Methyl groups can be incorporated into organic compounds by an SN2 reaction The SN2 reaction is a type of nucleophilic substitution, where a lone pair from a nucleophile attacks an electron deficient electrophilic center and bonds to it, expelling another group called a leaving group. Thus the incoming group replaces the leaving group in one step. Since two reacting species are involved in the slow, rate-determining step on iodomethane Methyl iodide, also called iodomethane, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. This dense volatile liquid is related to methane by replacement of one hydrogen atom by an atom of iodine. Its dipole moment is 1.59 D, and its refractive index is 1.5304 , 1.5293 (21 °C, D). Methyl iodide is miscible, or by the reaction of methyl lithium Methyllithium is an organolithium reagent with the empirical formula CH3Li. This s-block organometallic compound adopts an oligomeric structure both in solution and in the solid state. This highly reactive compound, invariably used as a solution in ethers, is a reagent in organic synthesis as well as organometallic chemistry. Operations involving or MeMgCl with a carbon atom that is substituted with a leaving group In chemistry, a leaving group is a molecular fragment that departs with a pair of electrons in heterolytic bond cleavage. Leaving groups can be anions or neutral molecules. Common anionic leaving groups are halides such as Cl−, Br−, and I−, and sulfonate esters, such as para-toluenesulfonate or "tosylate" . Common neutral molecule.
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Reactivity
The methyl group can be found in 3 forms: anion An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge, cation An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge and radical In chemistry, radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Radicals may have positive, negative or zero charge. By convention, metals and their ions or complexes with unpaired electrons are not radicals. The unpaired electrons cause radicals to be highly chemically reactive. The anion has 8 electrons, the radical 7 and the cation 6. They are all reactive due to there being no stabilising effects such as induction or delocalization.
The introduction of methyl groups as substituents into a compound usually increases its lipophilicity Lipophilicity, , refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. These non-polar solvents are themselves lipophilic — the axiom that like dissolves like generally holds true. Thus lipophilic substances tend to dissolve in other lipophilic substances, while and reduces its solubility in water. It should ease its absorption into biological membranes and make its release into aqueous surroundings more difficult. Incorporating a methyl group into a molecule can have any of three effects, each increasing its reactivity (the rate of its metabolism Metabolism is the set of chemical reactions that happen in living organisms to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories. Catabolism breaks down organic matter, for example to harvest energy in cellular):
- by oxidizing Redox describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process, such as the oxidation of carbon to yield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), or a complex process such as the oxidation of sugar(C6H12O6) in the the methyl group,
- by demethylation (the transfer of the methyl group to another compound), or
- by reduction Redox reactions describe all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process, such as the oxidation of carbon to yield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), or a complex process such as the oxidation of sugar(C6H12O6) in, reducing the analogue.
The reactivity of a methyl group depends on what it is attached to. When occurring in 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, it is quite unreactive and resists all but the strongest of acids, bases, oxidizing agents, and reducing agents. But, in toluene Toluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. Chemically it is a mono-substituted benzene derivative, i.e. one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3, C6H5 where the six carbon atoms are arranged in a cyclic ring structure. This hydrophobic, highly-stable and aromatic hydrocarbon unit can be found in many organic compounds. It can be thought of as being derived from benzene . In fact, in chemical literature benzene itself is sometimes denoted as PhHCH3, the methyl group is considerably more reactive, due to the electron-donating propensity of the ring. Electrophilic reagents are then able to attack the methyl group. For example, oxidation with permanganate A permanganate is the general name for a chemical compound containing the manganate ion, (MnO4−). Because manganese is in the +7 oxidation state, the manganate(VII) ion is a strong oxidizing agent. The ion has tetrahedral geometry. Permanganate solutions are purple in color and are stable in neutral or slightly alkaline media converts the methyl group to carboxyl (-COOH), to produce benzoic acid Benzoic acid, C7H6O2 , is a colorless crystalline solid and the simplest aromatic carboxylic acid. The name derived from gum benzoin, which was for a long time the only source for benzoic acid. This weak acid and its salts are used as a food preservative. Benzoic acid is an important precursor for the synthesis of many other organic substances.
Syntheses
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The methylium cation (CH3+) can be formed using an effective leaving group in a SN2 reaction, such as methyl iodide Methyl iodide, also called iodomethane, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. This dense volatile liquid is related to methane by replacement of one hydrogen atom by an atom of iodine. Its dipole moment is 1.59 D, and its refractive index is 1.5304 , 1.5293 (21 °C, D). Methyl iodide is miscible, MeI or methyl tosylate A tosyl group is CH3C6H4SO2. This group is usually derived from the compound 4-toluenesulfonyl chloride, CH3C6H4SO2Cl, which forms esters and amides of toluenesulfonic acid. The para orientation illustrated (p-toluenesulfonyl) is most common, and by convention tosyl refers to the p-toluenesulfonyl group. Tosylate refers to the anion of p-, MeOTs.
The methanide anion (CH3-), also known as carbanide is highly unstable and an extremely strong base. Grignard reagents The Grignard reaction is an organometallic chemical reaction in which alkyl- or aryl-magnesium halides act as nucleophiles and attack electrophilic carbon atoms that are present within polar bonds (e.g. in a carbonyl group as in the example shown below) to yield a carbon-carbon bond, thus altering hybridization about the reaction center. The or organolithium reagent can be considered to be mostly ionic and act as alkyl anions. Methanide is not to be confused with methanetetraide (carbide), which is completely depronotoned methane. An example of a methanide is the highly reactive, lithium methanide Methyllithium is an organolithium reagent with the empirical formula CH3Li. This s-block organometallic compound adopts an oligomeric structure both in solution and in the solid state. This highly reactive compound, invariably used as a solution in ethers, is a reagent in organic synthesis as well as organometallic chemistry. Operations involving.
Methyl radical
The methyl radical In chemistry, radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Radicals may have positive, negative or zero charge. By convention, metals and their ions or complexes with unpaired electrons are not radicals. The unpaired electrons cause radicals to be highly chemically reactive is the substance CH3 on its own, with an unpaired electron. Though it readily dimerizes to ethane Ethane is a chemical compound with chemical formula C2H6. It is the only two-carbon alkane that is an aliphatic hydrocarbon. At standard temperature and pressure, ethane is a colorless, odorless gas, it is stable enough (unlike atomic hydrogen) to be observed as a dilute gas. It can be produced by thermal decomposition of certain compounds, especially those with an -N=N- linkage, which lose the extremely stable dinitrogen molecule on heating.
Etymology
French France is a founding member state of the European Union and is the largest one by area. France has been a major power for several centuries with strong cultural, economic, military and political influence in Europe and in the world. During the 17th and 18th centuries, France colonised great parts of North America; during the 19th and early 20th chemists Jean-Baptiste Dumas Jean Baptiste André Dumas was a French chemist, best known for his works on organic analysis and synthesis, as well as the determination of atomic weights (relative atomic masses) and molecular weights by measuring vapor densities. He also developed a method for the analysis of nitrogen in compounds and Eugene Peligot Eugène-Melchior Péligot , also known as Eugène Péligot, was a French chemist who isolated the first sample of uranium metal in 1841, after determining methanol's chemical structure, introduced "methylene" from the Greek methy = "wine" + hȳlē = wood (patch of trees) with the intention of highlighting its origins, "alcohol made from wood (substance)." The term "methyl" was derived in about 1840 by back-formation In etymology, back-formation is the process of creating a new lexeme by removing actual or supposed affixes. The resulting neologism is called a back-formation, a term coined by James Murray in 1889. (OED online first definition of 'back formation' is from the definition of to burgle which was first published in 1889.) from methylene, and was then applied to describe "methyl alcohol."
See also
- Methanol Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with formula C
- 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
Categories: Functional groups | Alkyl groups
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Mon, 16 Aug 2010 20:03:11 GMT+00:00
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