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Double Bond Rule
In chemistry, the double bond rule states that elements with a principal quantum number greater than 2 for their valence electrons (period 3 elements and higher) tend not to form multiple bonds (e.g. double bonds and triple bonds). The double bonds, when they exist, are often weak due to poor orbital overlap. Although such compounds are not intrinsically unstable, they instead tend to polymerize. An example is the rapid polymerization that occurs upon condensation of disulfur, the heavy analogue of . Numerous violations to the rule exist. Other meanings Another unrelated double bond rule exists that relates to the enhanced reactivity of sigma bonds attached to an atom adjacent to a double bond. In bromoalkenes, the C–Br bond is very stable, but in an allyl bromide, this bond is very reactive. Likewise, bromobenzenes are generally inert, whereas benzylic bromides are reactive. The first to observe the phenomenon was Conrad Laar Conrad Peter Laar (22 March 1853 – 11 Fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a Chemical reaction, reaction with other Chemical substance, substances. Chemistry also addresses the nature of chemical bonds in chemical compounds. In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both Basic research, basic and Applied science, applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diborene
Diborane(2) or diborene is a theoretical/hypothetical inorganic compound with the formula B2H2. Diborenes also refers to a series of molecules with a formula R:(BH)=(BH):R, where R is an organic group. B2H2 are unstable under ambient conditions. They are synthesized by pulsed laser ablation of boron in a mixed hydrogen-argon gas atmosphere. Upon cooling the mixture, the argon gas changes into a solid, thereby stabilizing the trapped diboranes. B2H2 is a linear molecule with a triplet ground state, as revealed by electron paramagnetic resonance Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a method for studying materials that have unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but the spi ..., and shows an antisymmetric stretching mode at 2679.9 cm–1. References Boranes {{theoretical-chem-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Azo Compound
Azo compounds are organic compounds bearing the functional group diazenyl (, in which R and R′ can be either aryl or alkyl groups). IUPAC defines azo compounds as: "Derivatives of diazene (diimide), , wherein both hydrogens are substituted by hydrocarbyl groups, e.g. azobenzene or diphenyldiazene." The more stable derivatives contain two aryl groups. The group is called an ''azo group'' (, ). Many textile and leather articles are dyed with azo dyes and pigments. Aryl azo compounds Aryl azo compounds are usually stable, crystalline species. Azobenzene is the prototypical aromatic azo compound. It exists mainly as the ''trans'' isomer, but upon illumination, converts to the ''cis'' isomer. Aromatic azo compounds can be synthesized by azo coupling, which entails an electrophilic substitution reaction where an aryl diazonium cation is attacked by another aryl ring, especially those substituted with electron-donating groups: :ArN2+ + Ar'H -> ArN=NAr' + H+ Since diazoniu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thioketone
In organic chemistry, thioketones (; also known as thiones or thiocarbonyls) are organosulfur compounds related to conventional ketones in which the oxygen has been replaced by a sulfur. Instead of a structure of , thioketones have the structure , which is reflected by the prefix "thio-" in the name of the functional group. Unhindered alkylthioketones typically tend to form polymers or rings. Structure and bonding The C=S bond length of thiobenzophenone is 1.63 Å, which is comparable to 1.64 Å, the C=S bond length of thioformaldehyde, measured in the gas phase. Due to steric interactions, the phenyl groups are not coplanar and the dihedral angle SC-CC is 36°. Unhindered dialkylthiones polymerize or oligomerize but thiocamphor is well characterized red solid. Consistent with the double bond rule, most alkyl thioketones are unstable with respect to dimerization.Organosulfur Chemistry I: Topics in Current Chemistry, 1999, Volume 204/1999, 127-181, The energy difference between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphaalkene
Phosphaalkenes (IUPAC name: alkylidenephosphanes) are organophosphorus compounds with double bonds between carbon and phosphorus(III) with the formula R2C=PR. In the compound phosphorine one carbon atom in benzene is replaced by phosphorus. The reactivity of phosphaalkenes is often compared to that of alkenes and not to that of imines because the HOMO of phosphaalkenes is not the phosphorus lone pair (as in imines the amine lone pair) but the double bond. Therefore like alkenes, phosphaalkenes engage in Wittig reactions, Peterson reactions, Cope rearrangements and Diels-Alder reactions. The first phosphaalkene discovered was a phosphabenzene, by Mërkl in 1969. The first localized phosphaalkene was reported in 1976 by Gerd Becker as a keto-enol tautomerism akin a Brook rearrangement: :: In the same year Harold Kroto established spectroscopically that thermolysis of Me2PH generates CH2=PMe. A general method for the synthesis of phosphaalkenes is by 1,2-elimination of suitab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organosilicon
Organosilicon compounds are organometallic compounds containing carbon–silicon bonds. Organosilicon chemistry is the corresponding science of their preparation and properties. Most organosilicon compounds are similar to the ordinary organic compounds, being colourless, flammable, hydrophobic, and stable to air. Silicon carbide is an ''inorganic'' compound. History In 1846 Von Ebelman's had synthesized Tetraethyl orthosilicate (Si(OC2H5)4). In 1863 Friedel and Crafts managed to make the first organosilieon compound with C-Si bonds which gone byound the syntheses of orthosilicic acid esters. The same year they also described a «polysilicic acid ether» in the preparation of ethyl- and methyl-o-silicic acid. The early extensive research in the field of organosilicon compounds was pioneerd in the beginning of 20th century by Frederic Kipping. He also had coined the term «silicone» (akin to ketones) in relation to these materials in 1904. In recognition of Kipping's achiev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxonium Ion
In chemistry, an oxonium ion is any cation containing an oxygen atom that has three bonds and 1+ formal charge. The simplest oxonium ion is the hydronium ion (). Alkyloxonium Hydronium is one of a series of oxonium ions with the formula R''n''H3−''n''O+. Oxygen is usually pyramidal with an sp3 hybridization. Those with ''n'' = 1 are called primary oxonium ions, an example being protonated alcohol (e.g. methanol). In acidic media, the oxonium functional group produced by protonating an alcohol can be a leaving group in the E2 elimination reaction. The product is an alkene. Extreme acidity, heat, and dehydrating conditions are usually required. Other hydrocarbon oxonium ions are formed by protonation or alkylation of alcohols or ethers (R−C−−R1R2). Secondary oxonium ions have the formula R2OH+, an example being protonated ethers. Tertiary oxonium ions have the formula R3O+, an example being trimethyloxonium. Tertiary alkyloxonium salts are useful alkylating a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a carbonyl group is often referred to as a carbonyl compound. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e.g. nickel carbonyl). The remainder of this article concerns itself with the organic chemistry definition of carbonyl, where carbon and oxygen share a double bond. Carbonyl compounds In organic chemistry, a carbonyl group characterizes the following types of compounds: Other organic carbonyls are urea and the carbamates, the derivatives of acyl chlorides chloroformates and phosgene, carbonate esters, thioesters, lactones, lactams, hydroxamates, and isocyanates. Examples of inorganic carbonyl compounds are carbon dioxide and carbonyl sulfide. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imine
In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bonds. Imines are common in synthetic and naturally occurring compounds and they participate in many reactions. Structure For ketimines and aldimines, respectively, the five core atoms (C2C=NX and C(H)C=NX, X = H or C) are coplanar. Planarity results from the sp2-hybridization of the mutually double-bonded carbon and the nitrogen atoms. The C=N distance is 1.29-1.31 Å for nonconjugated imines and 1.35 Å for conjugated imines. By contrast, C-N distances in amines and nitriles are 1.47 and 1.16 Å, respectively. Rotation about the C=N bond is slow. Using NMR spectroscopy, both E- and Z-isomers of aldimines have been detected. Owing to steric effects, the E isomer is favored. Nomenclature and classification The term "imine" was coine ... [...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 with '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesityl
Mesitylene or 1,3,5-trimethylbenzene is a derivative of benzene with three methyl substituents positioned symmetrically around the ring. The other two isomeric trimethylbenzenes are 1,2,4-trimethylbenzene (pseudocumene) and 1,2,3-trimethylbenzene (hemimellitene). All three compounds have the formula C6H3(CH3)3, which is commonly abbreviated C6H3Me3. Mesitylene is a colorless liquid with sweet aromatic odor. It is a component of coal tar, which is its traditional source. It is a precursor to diverse fine chemicals. The mesityl group (Mes) is a substituent with the formula C6H2Me3 and is found in various other compounds. Preparation Mesitylene is prepared by transalkylation of xylene over solid acid catalyst:Karl Griesbaum, Arno Behr, Dieter Biedenkapp, Heinz-Werner Voges, Dorothea Garbe, Christian Paetz, Gerd Collin, Dieter Mayer, Hartmut Höke “Hydrocarbons” in Ullmann's Encyclopedia of Industrial Chemistry 2002 Wiley-VCH, Weinheim. . :2 C6H4(CH3)2 ⇌ C6H3(CH ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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