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Gomberg's Dimer
Gomberg's dimer is the organic compound with the formula Ph2C=C6H5-CPh3, where Ph = C6H5. It is a yellow solid that is air-stable for hours at room temperature and soluble in organic solvents. The compound achieved fame as the dimer of triphenylmethyl radical, which was prepared by Moses Gomberg in his quest for hexaphenylethane. Its quinoid structure has been determined by X-ray crystallography. The C-C bond that reversibly breaks is rather long at 159.7 picometers. Synthesis and reactions Gomberg's dimer can be prepared quantitatively by treating trityl bromide with powdered copper or silver: :2Ph3CBr + 2Cu → Ph2C=C6H5-CPh3 + 2CuBr Gomberg's dimer reversibly dissociates to the triphenylmethyl radical in organic solvents: : See also * Hexaphenylethane Hexaphenylethane is a hypothetical organic compound consisting of an ethane core with six phenyl substituents. All attempts at its synthesis have been unsuccessful. The trityl free radical, Ph3C, was originall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenyl
In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula C6 H5, and is often represented by the symbol Ph. Phenyl group is closely related to benzene and can be viewed as a benzene ring, minus a hydrogen, which may be replaced by some other element or compound to serve as a functional group. Phenyl group has six carbon atoms bonded together in a hexagonal planar ring, five of which are bonded to individual hydrogen atoms, with the remaining carbon bonded to a substituent. Phenyl groups are commonplace in organic chemistry. Although often depicted with alternating double and single bonds, phenyl group is chemically aromatic and has equal bond lengths between carbon atoms in the ring. Nomenclature Usually, a "phenyl group" is synonymous with C6H5− and is represented by the symbol Ph or, archaically, Φ. Benzene is sometimes denoted as PhH. Phenyl groups are generally attached to other atoms or groups. For example, triphenylmethane (Ph3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimer (chemistry)
A dimer () ('' di-'', "two" + ''-mer'', "parts") is an oligomer consisting of two monomers joined by bonds that can be either strong or weak, covalent or intermolecular. Dimers also have significant implications in polymer chemistry, inorganic chemistry, and biochemistry. The term ''homodimer'' is used when the two molecules are identical (e.g. A–A) and ''heterodimer'' when they are not (e.g. A–B). The reverse of dimerization is often called dissociation. When two oppositely charged ions associate into dimers, they are referred to as ''Bjerrum pairs'', after Niels Bjerrum. Noncovalent dimers Anhydrous carboxylic acids form dimers by hydrogen bonding of the acidic hydrogen and the carbonyl oxygen. For example, acetic acid forms a dimer in the gas phase, where the monomer units are held together by hydrogen bonds. Under special conditions, most OH-containing molecules form dimers, e.g. the water dimer. Excimers and exciplexes are excited structures with a short lifetime. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triphenylmethyl Radical
The triphenylmethyl radical (often shorted to trityl radical) is an organic compound with the formula (C6H5)3C. It is a persistent radical. It was the first radical ever to be described in organic chemistry. Because of its accessibility, the trityl radical has been heavily exploited. Preparation and properties It can be prepared by homolysis of triphenylmethyl chloride 1 by a metal like silver or zinc in benzene or diethyl ether. The radical 2 forms a chemical equilibrium with the quinoid-type dimer 3 (Gomberg's dimer). In benzene the concentration of the radical is 2%. Solutions containing the radical are yellow; when the temperature of the solution is raised, the yellow color becomes more intense as the equilibrium is shifted in favor of the radical (in accordance with Le Chatelier's principle). When exposed to air, the radical rapidly oxidizes to the peroxide, and the color of the solution changes from yellow to colorless. Likewise, the radical reacts with iodine to tri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moses Gomberg
Moses Gomberg (February 8, 1866 – February 12, 1947) was a chemistry professor at the University of Michigan. He was elected to the National Academy of Sciences and served as president of the American Chemical Society. Early life and education He was born in Yelisavetgrad, Russian Empire to a Jewish merchant family. His father was Hershko (Hirsh) Gomberg and his mother was Maryam-Ethel Reznikova. In 1884, the family emigrated to Chicago to escape the pogroms following the assassination of Czar Alexander II. In Chicago he worked at the Stock Yards while attending Lake High School. In 1886, Moses entered the University of Michigan, where he obtained his B.Sc. in 1890 and his doctorate in 1894 under the supervision of A. B. Prescott. His thesis, titled "''Trimethylxanthine and Some of its Derivatives''", dealt with the derivatization of caffeine. Career Appointed an instructor in 1893, Gomberg worked at the University of Michigan for the duration of his professional academic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexaphenylethane
Hexaphenylethane is a hypothetical organic compound consisting of an ethane core with six phenyl substituents. All attempts at its synthesis have been unsuccessful. The trityl free radical, Ph3C, was originally thought to dimerize to form hexaphenylethane. However, an inspection of the NMR spectrum of this dimer reveals that it is in fact a non-symmetrical species, Gomberg's dimer instead. A substituted derivative of hexaphenylethane, hexakis(3,5-di-''t''-butylphenyl)ethane, has however been prepared. It features a very long central C–C bond at 167 pm (compared to the typical bond length of 154 pm). Attractive London dispersion forces between the ''t''-butyl substituents are believed to be responsible for the stability of this very hindered molecule. See also * Tetraphenylmethane Tetraphenylmethane is an organic compound consisting of a methane core with four phenyl substituents. It was first synthesized by Moses Gomberg in 1898. Synthesis Gomberg's class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quinoid
In organic chemistry, quinoids are a class of chemical compounds that are derived from quinone. Unlike benzenoid structures, the quinoid part is not aromatic. See also * Benzenoid * Aromatic compound Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past grouping ... Cyclic compounds {{Organic-compound-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Crystallography
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorder, and various other information. Since many materials can form crystals—such as salts, metals, minerals, semiconductors, as well as various inorganic, organic, and biological molecules—X-ray crystallography has been fundamental in the development of many scientific fields. In its first decades of use, this method determined the size of atoms, the lengths and types of chemical bonds, and the atomic-scale differences among various mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Picometer
The picometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: pm) or picometer (American spelling) is a unit of length in the International System of Units (SI), equal to , or one trillionth of a metre, which is the SI base unit of length. The picometre is one thousand femtometres, one thousandth of a nanometre ( nm), one millionth of a micrometre (also known as a micron), one billionth of a millimetre, and one trillionth of a metre. The symbol μμ was once used for it. It is also one hundredth of an ångström, an internationally known (but non-SI) unit of length. Use The picometre's length is of an order so small that its application is almost entirely confined to particle physics, quantum physics, chemistry and acoustics. Atoms are between 62 and 520 pm in diameter, and the typical length of a carbon–carbon single bond is 154 pm. Smaller units still may be used to describe smaller particles (some of which are t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gomberg Dimer Dissociation
Gomberg is a surname. It may refer to: *David Gomberg (born 1953), American small business owner, kite flier and politician * Guy Gomberg (born 1990), Israeli footballer * Harold Gomberg (1916–1985), American oboist (brother of Ralph) * Joan Gomberg (born 1957), American research geophysicist *Moses Gomberg (1866–1947), American chemist * Ralph Gomberg (1921–2006), American oboist (brother of Harold) *Sheldon Gomberg, music producer and engineer and bassist *Sy Gomberg (1918–2001), American film screenwriter, producer and activist *Tooker Gomberg Tooker Gomberg (August 12, 1955 – March 4, 2004) was a Canadian politician and environmental activist. A native of Montreal, Quebec, a graduate of Herzliah High School and a liberal-arts graduate of Hampshire College (1980), Gomberg founded one ... (1955–2004), Canadian politician and environmental activist {{surname [Baidu] |
Hexaphenylethane
Hexaphenylethane is a hypothetical organic compound consisting of an ethane core with six phenyl substituents. All attempts at its synthesis have been unsuccessful. The trityl free radical, Ph3C, was originally thought to dimerize to form hexaphenylethane. However, an inspection of the NMR spectrum of this dimer reveals that it is in fact a non-symmetrical species, Gomberg's dimer instead. A substituted derivative of hexaphenylethane, hexakis(3,5-di-''t''-butylphenyl)ethane, has however been prepared. It features a very long central C–C bond at 167 pm (compared to the typical bond length of 154 pm). Attractive London dispersion forces between the ''t''-butyl substituents are believed to be responsible for the stability of this very hindered molecule. See also * Tetraphenylmethane Tetraphenylmethane is an organic compound consisting of a methane core with four phenyl substituents. It was first synthesized by Moses Gomberg in 1898. Synthesis Gomberg's class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
