|
Pinacol Coupling Reaction
A pinacol coupling reaction is an organic reaction in which a carbon–carbon bond is formed between the carbonyl groups of an aldehyde or a ketone in presence of an electron donor in a free radical process. The reaction product is a vicinal diol. The reaction is named after pinacol (also known as 2,3-dimethyl-2,3-butanediol or tetramethylethylene glycol), which is the product of this reaction when done with acetone as reagent. The reaction is usually a homocoupling but intramolecular cross-coupling reactions are also possible. Pinacol was discovered by Wilhelm Rudolph Fittig in 1859. Reaction mechanism The first step in the reaction mechanism is a one-electron reduction of the carbonyl group by a reducing agent —such as magnesium— to a ketyl radical anion species. Two ketyl groups react in a coupling reaction yielding a vicinal diol with both hydroxyl groups deprotonated. Addition of water or another proton donor gives the diol. With magnesium as an electron donor, the initia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinacol Coupling Of Benzaldehyde
Pinacol is a white solid organic compound. It is a diol that has hydroxyl groups (-OH) on vicinal carbon atoms. Preparation It may be produced by the pinacol coupling reaction from acetone: Reactions As a vicinal-diol, it can rearrange to pinacolone by the pinacol rearrangement, e.g. by heating with sulfuric acid: Pinacol can be used with borane and boron trichloride to produce useful synthetic intermediates such as pinacolborane, bis(pinacolato)diboron,{{OrgSynth , collvol = 10 , collvolpages = 115 , year = 2004 , prep = v77p0176 , title = Bis(pinacolato)diboron , author1 = Tatsuo Ishiyama, author2= Miki Murata, author3=Taka-aki Ahiko, author4-link= Norio Miyaura, author4=Norio Miyaura and pinacolchloroborane. See also * Semipinacol rearrangement The semipinacol rearrangement is a rearrangement reaction in organic chemistry involving a heterosubstituted alcohol of the type R1R2(HO)C–C(X)R3R4. The hetero substituent can be a halogen (Cl, Br, I), a tosylate, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnesium Hydroxide
Magnesium hydroxide is the inorganic compound with the chemical formula Mg(OH)2. It occurs in nature as the mineral brucite. It is a white solid with low solubility in water (). Magnesium hydroxide is a common component of antacids, such as milk of magnesia. Preparation Treating the solution of different soluble magnesium salts with alkaline water induces the precipitation of the solid hydroxide Mg(OH)2: :Mg2+ + 2OH− → Mg(OH)2 As is the second most abundant cation present in seawater after , it can be economically extracted directly from seawater by alkalinisation as described here above. On an industrial scale, Mg(OH)2 is produced by treating seawater with lime (Ca(OH)2). A volume of (or 160,000 US gallons) of seawater gives about one ton of Mg(OH)2. Ca(OH)2 is far more soluble than Mg(OH)2 and drastically increases the pH value of seawater from 8.2 to 12.5. The less soluble precipitates because of the common ion effect due to the added by the dissolution of : : ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Montmorillonite
Montmorillonite is a very soft phyllosilicate group of minerals that form when they precipitate from water solution as microscopic crystals, known as clay. It is named after Montmorillon in France. Montmorillonite, a member of the smectite group, is a 2:1 clay, meaning that it has two tetrahedral sheets of silica sandwiching a central octahedral sheet of alumina. The particles are plate-shaped with an average diameter around 1 μm and a thickness of 0.96 nm; magnification of about 25,000 times, using an electron microscope, is required to "see" individual clay particles. Members of this group include, amongst others, saponite, nontronite, beidellite, and hectorite. Montmorillonite is a subclass of smectite, a 2:1 phyllosilicate mineral characterized as having greater than 50% octahedral charge; its cation exchange capacity is due to isomorphous substitution of Mg for Al in the central alumina plane. The substitution of lower valence cations in such instances leaves the n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meso Compound
A meso compound or meso isomer is a non-optically active member of a set of stereoisomers, at least two of which are optically active. This means that despite containing two or more stereocenters, the molecule is not chiral. A meso compound is "superposable" on its mirror image (not to be confused with superimposable, as any two objects can be superimposed over one another regardless of whether they are the same). Two objects can be superposed if all aspects of the objects coincide and it does not produce a "(+)" or "(-)" reading when analyzed with a polarimeter. The name is derived from the Greek ''mésos'' meaning “middle”. For example, tartaric acid can exist as any of three stereoisomers depicted below in a Fischer projection. Of the four colored pictures at the top of the diagram, the first two represent the meso compound (the 2'' R'',3'' S'' and 2'' S'',3'' R'' isomers are equivalent), followed by the optically active pair of levotartaric acid (L-(''R,R'')-(+)-tartaric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diastereomer
In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters and are not mirror images of each other. When two diastereoisomers differ from each other at only one stereocenter, they are epimers. Each stereocenter gives rise to two different configurations and thus typically increases the number of stereoisomers by a factor of two. Diastereomers differ from enantiomers in that the latter are pairs of stereoisomers that differ in all stereocenters and are therefore mirror images of one another. Enantiomers of a compound with more than one stereocenter are also diastereomers of the other stereoisomers of that compound that are not their mirror image (that is, excluding the opposing enantiomer). Diastereomers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Room Temperature
Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a person when they are wearing typical indoor clothing. Human comfort can extend beyond this range depending on humidity, air circulation and other factors. Food or beverages may be served at ''room temperature'', meaning neither heated nor cooled. In certain fields, like science and engineering, and within a particular context, ''room temperature'' can mean different agreed-upon ranges. In contrast, ''ambient temperature'' is the actual temperature, as measured by a thermometer, of the air (or other medium and surroundings) in any particular place. The ambient temperature (e.g. an unheated room in winter) may be very different from an ideal ''room temperature''. Comfort temperatures '' The American Heritage Dictionary of the English Language'' identifies room temperature as around , while the ''Oxford English Dictionary'' states that it is "co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterogeneous
Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, size, weight, height, distribution, texture, language, income, disease, temperature, radioactivity, architectural design, etc.); one that is heterogeneous is distinctly nonuniform in at least one of these qualities. Heterogeneous Mixtures, in chemistry, is where certain elements are unwillingly combined and, when given the option, will separate. Etymology and spelling The words ''homogeneous'' and ''heterogeneous'' come from Medieval Latin ''homogeneus'' and ''heterogeneus'', from Ancient Greek ὁμογενής (''homogenēs'') and ἑτερογενής (''heterogenēs''), from ὁμός (''homos'', “same”) and ἕτερος (''heteros'', “other, another, different”) respectively, followed by γένος (''genos'', “kind”); - ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has a great affinity towards oxygen, and forms a protective layer of oxide on the surface when exposed to air. Aluminium visually resembles silver, both in its color and in its great ability to reflect light. It is soft, non-magnetic and ductile. It has one stable isotope, 27Al; this isotope is very common, making aluminium the twelfth most common element in the Universe. The radioactivity of 26Al is used in radiodating. Chemically, aluminium is a post-transition metal in the boron group; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state. The aluminium cation Al3+ is small and highly charged; as such, it is polarizing, and bonds aluminium forms tend towards covalency. The strong affinity toward ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vanadium(III) Chloride
Vanadium trichloride is the inorganic compound with the formula VCl3. This purple salt is a common precursor to other vanadium(III) complexes. Structure VCl3 has the common BiI3 structure, a motif that features hexagonally closest-packed chloride framework with vanadium ions occupying the octahedral holes. VBr3 and VI3 adopt the same structure, but VF3 features a structure more closely related to ReO3. VCl3 is paramagnetic and has two unpaired electrons. Preparation and reactions VCl3 is prepared by heating VCl4 at 160–170 °C under a flowing stream of inert gas, which sweeps out the Cl2. The bright red liquid converts to a purple solid. Heating of VCl3 decomposes with volatilization of VCl4, leaving VCl2. Upon heating under H2 at 675 °C (but less than 700 °C), VCl3 reduces to greenish VCl2. :: 2 VCl3 + H2 → 2 VCl2 + 2 HCl Comproportionation of vanadium trichloride and vanadium(V) oxides gives vanadium oxydichloride: :V2O5 + VOCl3 + 3 VCl3 → ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinacol Reaction Mechanism
Pinacol is a white solid organic compound. It is a diol that has hydroxyl groups (-OH) on vicinal carbon atoms. Preparation It may be produced by the pinacol coupling reaction from acetone: Reactions As a vicinal-diol, it can rearrange to pinacolone by the pinacol rearrangement, e.g. by heating with sulfuric acid: Pinacol can be used with borane and boron trichloride to produce useful synthetic intermediates such as pinacolborane, bis(pinacolato)diboron,{{OrgSynth , collvol = 10 , collvolpages = 115 , year = 2004 , prep = v77p0176 , title = Bis(pinacolato)diboron , author1 = Tatsuo Ishiyama, author2= Miki Murata, author3=Taka-aki Ahiko, author4-link= Norio Miyaura, author4=Norio Miyaura and pinacolchloroborane. See also * Semipinacol rearrangement The semipinacol rearrangement is a rearrangement reaction in organic chemistry involving a heterosubstituted alcohol of the type R1R2(HO)C–C(X)R3R4. The hetero substituent can be a halogen (Cl, Br, I), a tosylate, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, and Biological Chemistry'. 1232 pages. Two general types of monoalkenes are distinguished: terminal and internal. Also called α-olefins, terminal alkenes are more useful. However, the International Union of Pure and Applied Chemistry (IUPAC) recommends using the name "alkene" only for acyclic hydrocarbons with just one double bond; alkadiene, alkatriene, etc., or polyene for acyclic hydrocarbons with two or more double bonds; cycloalkene, cycloalkadiene, etc. for cyclic ones; and "olefin" for the general class – cyclic or acyclic, with one or more double bonds. Acyclic alkenes, with only one double bond and no other functional groups (also known as mono-enes) form a homologous series of hydrocarbons with the general formula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanium(IV) Chloride
Titanium tetrachloride is the inorganic compound with the formula . It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. is a volatile liquid. Upon contact with humid air, it forms thick clouds of titanium dioxide () and hydrochloric acid, a reaction that was formerly exploited for use in smoke machines. It is sometimes referred to as "tickle" or "tickle 4" due to the phonetic resemblance of its molecular formula () to the word. Properties and structure is a dense, colourless distillable liquid, although crude samples may be yellow or even red-brown. It is one of the rare transition metal halides that is a liquid at room temperature, being another example. This property reflects the fact that molecules of weakly self-associate. Most metal chlorides are polymers, wherein the chloride atoms bridge between the metals. Its melting and boiling points are similar to those of . has a "closed" electronic shell, with the same numbe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
