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Pfeiffer Effect
The Pfeiffer effect is an optical phenomenon whereby the presence of an optically active compound influences the optical rotation of a racemic mixture of a second compound. Racemic mixtures do not rotate plane polarized light, but the equilibrium concentration of the two enantiomers can shift from unity in the presence of a strongly interacting chiral species. Paul Pfeiffer, a student of Alfred Werner and inventor of the salen ligand, reported this phenomenon. The first example of the effect is credited to Eligio Perucca, who observed optical rotations in the visible part of the spectrum when crystals of sodium chlorate, which are chiral and colourless, were stained with a racemic In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ... dye.Chemical & Engineering News, Vol. 86 No. 33, 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Rotatory Dispersion
Optical rotatory dispersion is the variation in the optical rotation of a substance with a change in the wavelength of light. Optical rotatory dispersion can be used to find the absolute configuration of metal complexes. For example, when plane-polarized white light from an overhead projector is passed through a cylinder of sucrose solution, a spiral rainbow is observed perpendicular to the cylinder. Principles of operation When white light passes through a polarizer, the extent of rotation of light depends on its wavelength. Short wavelengths are rotated more than longer wavelengths, per unit of distance. Because the wavelength of light determines its color, the variation of color with distance through the tube is observed. This dependence of specific rotation on wavelength is called optical rotatory dispersion. In all materials the rotation varies with wavelength. The variation is caused by two quite different phenomena. The first accounts in most cases for the majority of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Racemic Mixture
In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. History The first known racemic mixture was racemic acid, which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid. He manually separated the crystals of a mixture by hand, starting from an aqueous solution of the sodium ammonium salt of racemate tartaric acid. Pasteur benefited from the fact that ammonium tartrate salt that gives enantiomeric crystals with distinct crystal forms (at 77 °F). Reasoning from the macroscopic scale down to the molecular, he reckoned that the molecules had to have non-superimposable mirror images. A sample with only a single enantiomer is an ''enantiomerically pure'' or ''enantiopure'' compound. Etymology From racemic acid found in grapes; from Latin ''racemus'', meani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Rotation
Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circular birefringence and circular dichroism are the manifestations of optical activity. Optical activity occurs only in chiral materials, those lacking microscopic mirror symmetry. Unlike other sources of birefringence which alter a beam's state of polarization, optical activity can be observed in fluids. This can include gases or solutions of chiral molecules such as sugars, molecules with helical secondary structure such as some proteins, and also chiral liquid crystals. It can also be observed in chiral solids such as certain crystals with a rotation between adjacent crystal planes (such as quartz) or metamaterials. When looking at the source of light, the rotation of the plane of polarization may be either to the right (dextrorotator ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paul Pfeiffer (chemist)
Paul Pfeiffer (21 April 1875 – 4 March 1951) was an influential German chemist. He received his Ph.D. at the University of Zurich, studying under Alfred Werner, the "father of coordination chemistry". His thesis, submitted in 1898, dealt with adducts of tin halides. Pfeiffer was considered Werner's most successful student and became Werner's assistant until, due to a dispute with his mentor, he left first for Rostock, then Karlsruhe, and finally Bonn. At Bonn, where he had studied as an undergraduate, he occupied Kekulé's chair. Pfeiffer's work spanned many themes. The Pfeiffer effect, which involves interactions between chiral solutes, is named after his discoveries. His group first made the salen ligands, which gave the first artificial oxygen carriers. He recognized that crystals, e.g. of zinc sulfide Zinc sulfide (or zinc sulphide) is an inorganic compound with the chemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alfred Werner
Alfred Werner (12 December 1866 – 15 November 1919) was a Swiss chemist who was a student at ETH Zurich and a professor at the University of Zurich. He won the Nobel Prize in Chemistry in 1913 for proposing the octahedral configuration of transition metal complexes. Werner developed the basis for modern coordination chemistry. He was the first inorganic chemist to win the Nobel prize, and the only one prior to 1973.https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1913/werner-bio.html Nobel Prize Retrieved 1 December 2012 Biography Werner was born in 1866 in Mulhouse, Alsace (which was then part of France, but which was annexed by Germany in 1871). He was raised as Roman Catholic. He was the fourth and last child of Jean-Adam Werner, a foundry worker, and his second wife, Salomé Jeanette Werner, who originated from a wealthy family. He went to Switzerland to study chemistry at the Swiss Federal Institute (Polytechnikum) in Zurich, but since this institute was n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salen Ligand
Salen refers to a tetradentate C2-symmetric ligand synthesized from salicylaldehyde (sal) and ethylenediamine (en). It may also refer to a class of compounds, which are structurally related to the classical salen ligand, primarily bis-Schiff bases. Salen ligands are notable for coordinating a wide range of different metals, which they can often stabilise in various oxidation states. For this reason salen-type compounds are used as metal deactivators. Metal salen complexes also find use as catalysts. Synthesis and properties H2salen may be synthesized by the condensation of ethylenediamine and salicylaldehyde. : Complexes of salen with metal cations may be made without isolating it from the reaction mixture. This is possible because the stability constant for the formation of the metal complexes are very high, due to the chelate effect. :H2L + Mn+ → ML(n−2)+ + 2 H+ where L stands for the ligand. The pyridine adduct of the cobalt(II) complex Co(salen)(py) ( salcomine) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemische Berichte
''Chemische Berichte'' (usually abbreviated as ''Ber.'' or ''Chem. Ber.'') was a German-language scientific journal of all disciplines of chemistry founded in 1868. It was one of the oldest scientific journals in chemistry, until it merged with ''Recueil des Travaux Chimiques des Pays-Bas'' to form ''Chemische Berichte/Recueil'' in 1997. ''Chemische Berichte/Recueil'' was then merged with other European journals in 1998 to form ''European Journal of Inorganic Chemistry''. History Founded in 1868 as ''Berichte der Deutschen Chemischen Gesellschaft'' (, CODEN BDCGAS), it operated under this title until 1928 (Vol. 61). The journal was then split into: * ''Berichte der Deutschen Chemischen Gesellschaft, A: Vereins-Nachrichten'' (, CODEN BDCAAS), and * ''Berichte der Deutschen Chemischen Gesellschaft, B: Abhandlungen'' (, CODEN BDCBAD). Vol. 78 and 79 (1945–1946) were omitted and not published due to World War II. The journal was renamed ''Chemische Berichte'' (, CODEN CHBEAM) in 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eligio Perucca
Eligio Perucca (28 March 1890 in Potenza – 5 January 1965 in Rome) was an Italian physics instructor and researcher at the University of Turin in Italy in the early decades of the twentieth century. He later served a professorship at the nearby Polytechnic University of Turin. He discovered an important principle in stereochemistry in 1919, but his contribution was overlooked and forgotten until recently. Life and career Perucca received a Ph.D. degree in physics from the University of Pisa at the astoundingly young age of 20. He became Assistant to Professor Naccari in 1911 at the University of Turin, a post he retained for 11 years. In 1922 Perucca succeeded Professor Majorana to the chair of Experimental Physics at the Polytechnic University of Turin. He retained that appointment until 1960. In addition he was Rector of the Polytechnic from 1947–1955, and largely devoted his energy to rebuilding the physical facilities which had been destroyed during World War II. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Chlorate
Sodium chlorate is an inorganic compound with the chemical formula Na ClO3. It is a white crystalline powder that is readily soluble in water. It is hygroscopic. It decomposes above 300 °C to release oxygen and leaves sodium chloride. Several hundred million tons are produced annually, mainly for applications in bleaching pulp to produce high brightness paper. Synthesis Industrially, sodium chlorate is produced by the electrolysis of concentrated sodium chloride solutions. All other processes are obsolete. The sodium chlorate process is not to be confused with the chloralkali process, which is an industrial process for the electrolytic production of sodium hydroxide and chlorine gas. The overall reaction can be simplified to the equation: First, chloride is oxidised to form intermediate hypochlorite, ClO−, which undergoes further oxidisation to chlorate along two competing reaction paths: (1) Anodic chlorate formation at the boundary layer between the electrolyte and t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chirality (chemistry)
In chemistry, a molecule or ion is called chiral () if it cannot be superposed on its mirror image by any combination of rotation (geometry), rotations, translation (geometry), translations, and some Conformational isomerism, conformational changes. This geometric property is called chirality (). The terms are derived from Ancient Greek χείρ (''cheir'') 'hand'; which is the canonical example of an object with this property. A chiral molecule or ion exists in two stereoisomers that are mirror images of each other, called enantiomers; they are often distinguished as either "right-handed" or "left-handed" by their absolute configuration or some other criterion. The two enantiomers have the same chemical properties, except when reacting with other chiral compounds. They also have the same physics, physical properties, except that they often have opposite optical activity, optical activities. A homogeneous mixture of the two enantiomers in equal parts is said to be racemic mixtu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Second Coordination Sphere
In coordination chemistry, the first coordination sphere refers to the array of molecules and ions (the ligands) directly attached to the central metal atom. The second coordination sphere consists of molecules and ions that attached in various ways to the first coordination sphere. First coordination sphere The first coordination sphere refers to the molecules that are attached directly to the metal. The interactions between the first and second coordination spheres usually involve hydrogen-bonding. For charged complexes, ion pairing is important. In hexamminecobalt(III) chloride ( o(NH3)6l3), the cobalt cation plus the 6 ammonia ligands comprise the first coordination sphere. The coordination sphere of this ion thus consists of a central MN6 core "decorated" by 18 N−H bonds that radiate outwards. Second coordination sphere Metal ions can be described as consisting of series of two concentric coordination spheres, the first and second. More distant from the second coor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarization (waves)
Polarization (also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. A simple example of a polarized transverse wave is vibrations traveling along a taut string ''(see image)''; for example, in a musical instrument like a guitar string. Depending on how the string is plucked, the vibrations can be in a vertical direction, horizontal direction, or at any angle perpendicular to the string. In contrast, in longitudinal waves, such as sound waves in a liquid or gas, the displacement of the particles in the oscillation is always in the direction of propagation, so these waves do not exhibit polarization. Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves (shear waves) in solids. An electromagnetic wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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