A cumulene is a hydrocarbon with three or more cumulative double bonds. They are analogous to allenes; the simplest molecule in this class is butatriene, called cumulene. Unlike most alkanes and alkenes, cumulenes tend to be rigid, comparable to alkynes, which makes them appealing for molecular nanotechnology. Polyynes are another kind of rigid carbon chains. Cumulenes are found in regions of outer space. Cumulenes containing heteroatoms are called heterocumulenes; the first reported synthesis of a butatriene is that of tetraphenylbutatriene in 1921. The most common synthetic method for butatriene synthesis is based on reductive coupling of a geminal dihalovinylidene. Tetraphenylbutatriene was reported synthesized in 1977 by homocoupling of 2,2-diphenyl-1,1,1-tribromoethane with elemental copper in dimethylformamide; the rigidity of cumulenes arises from the fact that the internal carbon atoms carry two double bonds. Their sp hybridisation results in two π bonds, one to each neighbor, which are perpendicular to each other.
This bonding reinforces a linear geometry of the carbon chain. Cumulenes with non-equivalent substituents on each end exhibit isomerism. If the number of consecutive double bonds is odd, there is cis–trans isomerism as for alkenes. If the number of consecutive double bonds is there is axial chirality as for allenes; the reactions of cumulene are those of simple isolated double bonds because the consecutive double bonds are not conjugated to each other. The first reported complex containing a vinylidene ligand was (Ph2C2Fe28, derived from the reaction of diphenylketene and Fe5 Structurally, this molecule resembles Fe29, wherein one μ-CO ligand is replaced by 1,1-diphenylvinylidene, Ph2C2; the first monometallic vinylidene complex was Mo2Cl. Cyclopropatriene and cyclohexahexaene, cyclic cumulenes
International Union of Pure and Applied Chemistry
The International Union of Pure and Applied Chemistry is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Council for Science. IUPAC is registered in Zürich and the administrative office, known as the "IUPAC Secretariat", is in Research Triangle Park, North Carolina, United States; this administrative office is headed by IUPAC's executive director Lynn Soby. IUPAC was established in 1919 as the successor of the International Congress of Applied Chemistry for the advancement of chemistry, its members, the National Adhering Organizations, can be national chemistry societies, national academies of sciences, or other bodies representing chemists. There are fifty-four National Adhering Organizations and three Associate National Adhering Organizations. IUPAC's Inter-divisional Committee on Nomenclature and Symbols is the recognized world authority in developing standards for the naming of the chemical elements and compounds.
Since its creation, IUPAC has been run by many different committees with different responsibilities. These committees run different projects which include standardizing nomenclature, finding ways to bring chemistry to the world, publishing works. IUPAC is best known for its works standardizing nomenclature in chemistry and other fields of science, but IUPAC has publications in many fields including chemistry and physics; some important work IUPAC has done in these fields includes standardizing nucleotide base sequence code names. IUPAC is known for standardizing the atomic weights of the elements through one of its oldest standing committees, the Commission on Isotopic Abundances and Atomic Weights; the need for an international standard for chemistry was first addressed in 1860 by a committee headed by German scientist Friedrich August Kekulé von Stradonitz. This committee was the first international conference to create an international naming system for organic compounds; the ideas that were formulated in that conference evolved into the official IUPAC nomenclature of organic chemistry.
IUPAC stands as a legacy of this meeting, making it one of the most important historical international collaborations of chemistry societies. Since this time, IUPAC has been the official organization held with the responsibility of updating and maintaining official organic nomenclature. IUPAC as such was established in 1919. One notable country excluded from this early IUPAC is Germany. Germany's exclusion was a result of prejudice towards Germans by the Allied powers after World War I. Germany was admitted into IUPAC during 1929. However, Nazi Germany was removed from IUPAC during World War II. During World War II, IUPAC was affiliated with the Allied powers, but had little involvement during the war effort itself. After the war and West Germany were readmitted to IUPAC. Since World War II, IUPAC has been focused on standardizing nomenclature and methods in science without interruption. In 2016, IUPAC denounced the use of chlorine as a chemical weapon; the organization pointed out their concerns in a letter to Ahmet Üzümcü, the director of the Organisation for the Prohibition of Chemical Weapons, in regards to the practice of utilizing chlorine for weapon usage in Syria among other locations.
The letter stated, "Our organizations deplore the use of chlorine in this manner. The indiscriminate attacks carried out by a member state of the Chemical Weapons Convention, is of concern to chemical scientists and engineers around the globe and we stand ready to support your mission of implementing the CWC." According to the CWC, "the use, distribution, development or storage of any chemical weapons is forbidden by any of the 192 state party signatories." IUPAC is governed by several committees. The committees are as follows: Bureau, CHEMRAWN Committee, Committee on Chemistry Education, Committee on Chemistry and Industry, Committee on Printed and Electronic Publications, Evaluation Committee, Executive Committee, Finance Committee, Interdivisional Committee on Terminology and Symbols, Project Committee, Pure and Applied Chemistry Editorial Advisory Board; each committee is made up of members of different National Adhering Organizations from different countries. The steering committee hierarchy for IUPAC is as follows: All committees have an allotted budget to which they must adhere.
Any committee may start a project. If a project's spending becomes too much for a committee to continue funding, it must take the issue to the Project Committee; the project committee either decides on an external funding plan. The Bureau and Executive Committee oversee operations of the other committees. IUPAC committee has a long history of naming organic and inorganic compounds. IUPAC nomenclature is developed so that any compound can be named under one set of standardized rules to avoid duplicate names; the first publication on IUPAC nomenclature of organic compounds was A Guide to IUPAC Nomenclature of Organic Compounds in 1900, which contained information from the International Congress of Applied Chemistry. IUPAC organic nomenclature has three basic parts: the substituents, carbon chain length and chemical ending; the substituents are any functional groups attached to the main carbon chain. The main carbon chain is the longest possible continuous chain; the chemical ending denotes. For example, the ending ane denotes a single bonded carbon chain, as in "hexane".
Another example of IUPAC organic no
Blue is one of the three primary colours of pigments in painting and traditional colour theory, as well as in the RGB colour model. It lies between green on the spectrum of visible light; the eye perceives blue when observing light with a dominant wavelength between 450 and 495 nanometres. Most blues contain a slight mixture of other colours; the clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called. Distant objects appear. Blue has been an important colour in decoration since ancient times; the semi-precious stone lapis lazuli was used in ancient Egypt for jewellery and ornament and in the Renaissance, to make the pigment ultramarine, the most expensive of all pigments. In the eighth century Chinese artists used cobalt blue to white porcelain. In the Middle Ages, European artists used it in the windows of Cathedrals. Europeans wore clothing coloured with the vegetable dye woad until it was replaced by the finer indigo from America.
In the 19th century, synthetic blue dyes and pigments replaced mineral pigments and synthetic dyes. Dark blue became a common colour for military uniforms and in the late 20th century, for business suits; because blue has been associated with harmony, it was chosen as the colour of the flags of the United Nations and the European Union. Surveys in the US and Europe show that blue is the colour most associated with harmony, confidence, infinity, the imagination and sometimes with sadness. In US and European public opinion polls it is the most popular colour, chosen by half of both men and women as their favourite colour; the same surveys showed that blue was the colour most associated with the masculine, just ahead of black, was the colour most associated with intelligence, knowledge and concentration. Blue is the colour of light between green on the visible spectrum. Hues of blue include ultramarine, closer to violet. Blue varies in shade or tint. Darker shades of blue include ultramarine, cobalt blue, navy blue, Prussian blue.
Blue pigments were made from minerals such as lapis lazuli and azurite, blue dyes were made from plants. Today most blue dyes are made by a chemical process; the modern English word blue comes from Middle English bleu or blewe, from the Old French bleu, a word of Germanic origin, related to the Old High German word blao. In heraldry, the word azure is used for blue. In Russian and some other languages, there is no single word for blue, but rather different words for light blue and dark blue. See Colour term. Several languages, including Japanese, Thai and Lakota Sioux, use the same word to describe blue and green. For example, in Vietnamese the colour of both tree leaves and the sky is xanh. In Japanese, the word for blue is used for colours that English speakers would refer to as green, such as the colour of a traffic signal meaning "go". Linguistic research indicates. Colour names developed individually in natural languages beginning with black and white, adding red, only much – as the last main category of colour accepted in a language – adding the colour blue when blue pigments could be manufactured reliably in the culture using that language.
Human eyes perceive blue when observing light which has a dominant wavelength of 450–495 nanometres. Blues with a higher frequency and thus a shorter wavelength look more violet, while those with a lower frequency and a longer wavelength appear more green. Pure blue, in the middle, has a wavelength of 470 nanometres. Isaac Newton included blue as one of the seven colours in his first description the visible spectrum, He chose seven colours because, the number of notes in the musical scale, which he believed was related to the optical spectrum, he included indigo, the hue between blue and violet, as one of the separate colours, though today it is considered a hue of blue. In painting and traditional colour theory, blue is one of the three primary colours of pigments, which can be mixed to form a wide gamut of colours. Red and blue mixed together form violet and yellow together form green. Mixing all three primary colours together produces a dark grey. From the Renaissance onwards, painters used this system to create their colours.
The RYB model was used for colour printing by Jacob Christoph Le Blon as early as 1725. Printers discovered that more accurate colours could be created by using combinations of magenta, cyan and black ink, put onto separate inked plates and overlaid one at a time onto paper; this method could produce all the colours in the spectrum with reasonable accuracy. In the 19th century the Scottish physicist James Clerk Maxwell found a new way of explaining colours, by the wa
A thial or thioaldehyde is a functional group in organic chemistry, similar to an aldehyde, RCH, in which a sulfur atom replaces the oxygen atom of the aldehyde. Thioaldehydes are more reactive than thioketones. Unhindered thioaldehydes are too reactive to be isolated — for example, thioformaldehyde, H2C=S, condenses to the cyclic trimer 1,3,5-trithiane. Thioacrolein, H2C=CHCH=S, formed by decomposition of allicin from garlic, undergoes a self Diels-Alder reaction giving isomeric vinyldithiins. While thioformaldehyde is reactive, it is found in interstellar space along with its mono- and di-deuterated isotopologues. With sufficient steric bulk, stable thioaldehydes can be isolated. In early work, the existence of thioaldehydes was inferred by trapping processes. For instance the reaction of Fc2P2S4 with benzaldehyde was proposed to form thiobenzaldehyde, which forms a cycloadduct with the dithiophosphine ylides to form a C2PS3 ring. Thioketone Thioenol Organosulfur compounds
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 refers to C2H2, known formally as ethyne using IUPAC nomenclature. Like other hydrocarbons, alkynes are hydrophobic but tend to be more reactive. Alkynes are characteristically more unsaturated than alkenes, thus they add two equivalents of bromine. Other reactions are listed below. In some reactions, alkynes are less reactive than alkenes. For example, in a molecule with an -ene and an -yne group, addition occurs preferentially at the -ene. Possible explanations involve the two π-bonds in the alkyne delocalising, which would reduce the energy of the π-system or the stability of the intermediates during the reaction, they show greater tendency to oligomerize than alkenes do.
The resulting polymers, called polyacetylenes are conjugated and can exhibit semiconducting properties. In acetylene, the H–C≡C bond angles are 180°. By virtue of this bond angle, alkynes are rod-like. Correspondingly, cyclic alkynes are rare. Benzyne is unstable; the C≡C bond distance of 121 picometers is much shorter than the C=C distance in alkenes or the C–C bond in alkanes. The triple bond is strong with a bond strength of 839 kJ/mol; the sigma bond contributes 369 kJ/mol, the first pi bond contributes 268 kJ/mol and the second pi-bond of 202 kJ/mol bond strength. Bonding discussed in the context of molecular orbital theory, which recognizes the triple bond as arising from overlap of s and p orbitals. In the language of valence bond theory, the carbon atoms in an alkyne bond are sp hybridized: they each have two unhybridized p orbitals and two sp hybrid orbitals. Overlap of an sp orbital from each atom forms one sp–sp sigma bond; each p orbital on one atom overlaps one on the other atom, forming two pi bonds, giving a total of three bonds.
The remaining sp orbital on each atom can form a sigma bond to another atom, for example to hydrogen atoms in the parent acetylene. The two sp orbitals project on opposite sides of the carbon atom. Internal alkynes feature carbon substituents on each acetylenic carbon. Symmetrical examples include 3-hexyne. Terminal alkynes have the formula RC2H. An example is methylacetylene. Terminal alkynes, like acetylene itself, are mildly acidic, with pKa values of around 25, they are far more acidic than alkenes and alkanes, which have pKa values of around 40 and 50, respectively. The acidic hydrogen on terminal alkynes can be replaced by a variety of groups resulting in halo-, silyl-, alkoxoalkynes; the carbanions generated by deprotonation of terminal alkynes are called acetylides. In systematic chemical nomenclature, alkynes are named with the Greek prefix system without any additional letters. Examples include octyne. In parent chains with four or more carbons, it is necessary to say. For octyne, one can either write oct-3-yne when the bond starts at the third carbon.
The lowest number possible is given to the triple bond. When no superior functional groups are present, the parent chain must include the triple bond if it is not the longest possible carbon chain in the molecule. Ethyne is called by its trivial name acetylene. In chemistry, the suffix -yne is used to denote the presence of a triple bond. In organic chemistry, the suffix follows IUPAC nomenclature. However, inorganic compounds featuring unsaturation in the form of triple bonds may be denoted by substitutive nomenclature with the same methods used with alkynes. "-diyne" is used when there are two triple bonds, so on. The position of unsaturation is indicated by a numerical locant preceding the "-yne" suffix, or'locants' in the case of multiple triple bonds. Locants are chosen. "-yne" is used as an infix to name substituent groups that are triply bound to the parent compound. Sometimes a number between hyphens is inserted before it to state which atoms the triple bond is between; this suffix arose as a collapsed form of the end of the word "acetylene".
The final" - e" disappears. Commercially, the dominant alkyne is acetylene itself, used as a fuel and a precursor to other compounds, e.g. acrylates. Hundreds of millions of kilograms are produced annually by partial oxidation of natural gas: 2 CH4 + 3/2 O2 → HC≡CH + 3 H2OPropyne industrially useful, is prepared by thermal cracking of hydrocarbons. Most other industrially useful alkyne derivatives are prepared from acetylene, e.g. via condensation with formaldehyde. Specialty alkynes are prepared by dehydrohalogenation of vicinal alkyl dihalides or vinyl halides. Metal acetylides can be coupled with primary alkyl halides. Via the Fritsch–Buttenberg–Wiechell rearrangement, alkynes are prepared from vinyl bromides. Alkynes can be prepared from aldehydes using the Corey–Fuchs reaction and from aldehydes or ketones by the Seyferth–Gilbert homologation. In the alkyne zipper reaction, alkynes are generated from other alkynes by treatment with a strong base. Featuring a reactive functional group, alkynes participate in many organic reactions.
Such use was pioneered by Ralph Raphael, who in 1955 wrote the first book describing their versatility as intermediates in synthesis. Alkynes character
In chemistry, an ethyl group is an alkyl substituent derived from ethane. It has the formula –CH2CH3 and is often abbreviated Et. Ethyl is used in the IUPAC nomenclature of organic chemistry for a saturated two-carbon moiety in a molecule, whilst the prefix "eth-" is used to indicate the presence of two carbon atoms in the molecule. Ethylation is the formation of a compound by introduction of the ethyl group; the most practiced example of this reaction is the ethylation of benzene with ethylene to yield ethylbenzene, a precursor to styrene, a precursor to polystyrene. 24.7 million tons of ethylbenzene were produced in 1999. Many ethyl-containing compounds are generated by electrophilic ethylation, i.e. treatment of nucleophiles with sources of Et+. Triethyloxonium tetrafluoroborate BF4 is such a reagent. For good nucleophiles, less electrophilic reagents are employed, such as ethyl halides. In unsymmetrical ethylated compounds, the methylene protons in the ethyl substituent are diastereotopic. Chiral reagents are known to stereoselectively modify such substituents.
The name of the group is derived from the Aether, the first-born Greek elemental god of air and "hyle", referring to "stuff". The name "ethyl" was coined in 1835 by the Swedish chemist Jöns Jacob Berzelius. Functional group
A methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms — CH3. In formulas, the group is abbreviated Me; such hydrocarbon groups occur in many organic compounds. It is a stable group in most molecules. While the methyl group is part of a larger molecule, it can be found on its own in any of three forms: anion, cation or radical; the anion has the radical seven and the cation six. All three forms are reactive and observed; the methylium cation is otherwise not encountered. Some compounds are considered to be sources of the CH3+ cation, this simplification is used pervasively in organic chemistry. For example, protonation of methanol gives a electrophilic methylating reagent: CH3OH + H+ → CH3+ + H2OSimilarly, methyl iodide and methyl triflate are viewed as the equivalent of the methyl cation because they undergo SN2 reactions by weak nucleophiles; the methanide anion exists only under exotic conditions. It can be produced by electrical discharge in ketene at low pressure and its enthalpy of reaction is determined to be about 252.2±3.3 kJ/mol.
In discussions mechanisms of organic reactions, methyl lithium and related Grignard reagents are considered to be salts of "CH3−". Such reagents are prepared from the methyl halides: 2 M + CH3X → MCH3 + MXwhere M is an alkali metal; the methyl radical has the formula CH3. It exists in dilute gases, but in more concentrated form it dimerizes to ethane, it can be produced by thermal decomposition of only certain compounds those with an -N=N- linkage. The reactivity of a methyl group depends on the adjacent substituents. Methyl groups can be quite unreactive. For example, in organic compounds, the methyl group resists attack by the strongest acids; the oxidation of a methyl group occurs in nature and industry. The oxidation products derived from methyl are CH2OH, CHO, CO2H. For example, permanganate converts a methyl group to a carboxyl group, e.g. the conversion of toluene to benzoic acid. Oxidation of methyl groups gives protons and carbon dioxide, as seen in combustion. Demethylation is a common process, reagents that undergo this reaction are called methylating agents.
Common methylating agents are dimethyl sulfate, methyl iodide, methyl triflate. Methanogenesis, the source of natural gas, arises via a demethylation reaction. Certain methyl groups can be deprotonated. For example, the acidity of the methyl groups in acetone is about 1020 more acidic than methane; the resulting carbanions are key intermediates in many reactions in organic synthesis and biosynthesis. Fatty acids are produced in this way; when placed in benzylic or allylic positions, the strength of the C-H bond is decreased, the reactivity of the methyl group increases. One manifestation of this enhanced reactivity is the photochemical chlorination of the methyl group in toluene to give benzyl chloride. In the special case where one hydrogen is replaced by deuterium and another hydrogen by tritium, the methyl substituent becomes chiral. Methods exist to produce optically pure methyl compounds, e.g. chiral acetic acid. Through the use of chiral methyl groups, the stereochemical course of several biochemical transformations have been analyzed.
A methyl group may rotate around the R—C-axis. This is a free rotation only in the simplest cases like gaseous CClH3. In most molecules, the remainder R breaks the C ∞ symmetry of the R—C-axis and creates a potential V that restricts the free motion of the three protons. For the model case of C2H6 this is discussed under the name ethane barrier. In condensed phases, neighbour molecules contribute to the potential. Methyl group rotation can be experimentally studied using quasielastic neutron scattering. French chemists Jean-Baptiste Dumas and Eugene Peligot, after determining methanol's chemical structure, introduced "methylene" from the Greek methy "wine" and hȳlē "wood, patch of trees" with the intention of highlighting its origins, "alcohol made from wood"; the term "methyl" was derived in about 1840 by back-formation from "methylene", was applied to describe "methyl alcohol". Methyl is the IUPAC nomenclature of organic chemistry term for an alkane molecule, using the prefix "meth-" to indicate the presence of a single carbon