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35-495: Periodates were discovered by Heinrich Gustav Magnus and C. F. Ammermüller; who first synthesised periodic acid in 1833. Classically, periodate was most commonly produced in the form of sodium hydrogen periodate ( Na 3 H 2 IO 6 ). This is commercially available, but can also be produced by the oxidation of iodates with chlorine and sodium hydroxide . Or, similarly, from iodides by oxidation with bromine and sodium hydroxide: Modern industrial scale production involves

70-435: A cyclic intermediate called a periodate ester. The formation of this may be affected by pH and temperature but is most strongly affected by the geometry of the substrate, with cis -diols reacting significantly faster than trans -diols. The reactions are exothermic and are typically performed at 0 °C. As periodate salts are only readily soluble in water reactions are generally performed in aqueous media. Where solubility

105-540: A dehydration reaction can take place to form the diperiodate (sometimes referred to as mesoperiodate). Under strongly acid conditions periodic acid can be protonated to give the orthoperiodonium cation. In both the ortho- and metaperiodate the iodine is hypervalent , as it forms more bonds than would classically be allowed. This has been explained in terms of dative bonds , confirming the absence of double bonding in these molecules. Exact structures vary depending on counter ions, however on average orthoperiodates adopt

140-645: A slightly deformed octahedral geometry with X-ray diffraction showing I–O bond lengths of 1.89  Å . Metaperiodates adopt a distorted tetrahedral geometry with an average I–O distance of 1.78 Å. Periodates can cleave carbon–carbon bonds on a variety of 1,2-difunctionalised alkanes. The most common example of this is diol cleavage , which was also the first to be discovered ( Malaprade reaction ). In addition to diols , periodates can cleave 1,2-hydroxy ketones , 1,2-diketones , α-keto acids , α-hydroxy acids , amino acids , 1,2-amino alcohols , and 1,2-diamines , to give aldehydes, ketones, and carboxylic acids. In

175-543: A variety of forms in aqueous media, with pH being a controlling factor. Orthoperiodate has a number of acid dissociation constants . The ortho- and metaperiodate forms also exist in equilibrium. For this reason orthoperiodate is sometimes referred to as the di hydrate of metaperiodate, written IO − 4 ·2H 2 O ; however, this description is not strictly accurate as X-ray crystallography of H 5 IO 6 shows 5 equivalent I−OH groups. At extremes of pH additional species can form. Under basic conditions

210-457: A wealthy merchant. In his youth he received private instruction in mathematics and natural science. At the University of Berlin he studied chemistry and physics, 1822–27, and obtained a doctorate for a dissertation on tellurium in 1827. His doctoral adviser was Eilhard Mitscherlich . He then went to Stockholm for a year as a visiting research fellow at the laboratory of Jöns Jakob Berzelius (who

245-405: Is a catalyst that facilitates the transition of a reactant from one phase into another phase where reaction occurs. Phase-transfer catalysis is a special form of catalysis and can act through homogeneous catalysis or heterogeneous catalysis methods depending on the catalyst used. Ionic reactants are often soluble in an aqueous phase but insoluble in an organic phase in the absence of

280-503: Is an issue periodic acid may be used, as this is soluble in alcohols; phase transfer catalysts are also effective in biphasic reaction mixtures. In extreme cases the periodate may be exchanged for lead tetraacetate which reacts in a similar manner and is soluble in organic solvents ( Criegee oxidation ). Periodate cleavage is often utilized in molecular biochemistry for the purposes of modifying saccharide rings, as many five- and six-membered sugars have vicinal diols . Historically it

315-443: Is not required because the mass transfer is not the rate determining step in this catalytic system. It is already demonstrated that this system works for alkene epoxidation without stirring or the addition of a co-solvent to drive liquid–liquid phase transfer. The active site located on the external surface of the zeolite particle were dominantly effective for the observed phase boundary catalytic system. Modified zeolite on which

350-495: Is primarily applicable to reactions at the interface of an aqueous phase and organic phase. In these cases, an approach such as PBC is needed due to the immiscibility of aqueous phases with most organic substrate. In PBC, the catalyst acts at the interface between the aqueous and organic phases. The reaction medium of phase boundary catalysis systems for the catalytic reaction of immiscible aqueous and organic phases consists of three phases; an organic liquid phase, containing most of

385-478: Is widely exploited industrially. Polyesters for example are prepared from acyl chlorides and bisphenol-A . Phosphothioate -based pesticides are generated by PTC-catalyzed alkylation of phosphothioates. One of the more complex applications of PTC involves asymmetric alkylations, which are catalyzed by chiral quaternary ammonium salts derived from cinchona alkaloids . Phase-boundary catalytic (PBC) systems can be contrasted with conventional catalytic systems. PBC

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420-794: The US Army announced that it would replace the environmentally harmful chemicals barium nitrate and potassium perchlorate with sodium metaperiodate for use in their tracer ammunition. Periodate is part of a series of oxyanions in which iodine can assume oxidation states of −1, +1, +3, +5, or +7. A number of neutral iodine oxides are also known. Heinrich Gustav Magnus Rudolf Clausius Eduard Hagenbach-Bischoff Wilhelm Heinrich Heintz Hermann Helmholtz Gustav Karsten Alexander Mitscherlich Arthur von Oettingen Georg Hermann Quincke Edward Schunck Heinrich Gustav Magnus ( German pronunciation: [ˈhaɪnʁɪç ˈɡʊsta(ː)f ˈma(ː)ɡnʊs] ; 2 May 1802 – 4 April 1870)

455-473: The electrochemical oxidation of iodates, on a lead dioxide ( PbO 2 ) anode, with the following standard electrode potential : Metaperiodates are typically prepared by the dehydration of sodium hydrogen periodate with nitric acid , or by dehydrating orthoperiodic acid by heating it to 100 °C under vacuum. They can also be generated directly from iodates by treatment with other strong oxidizing agents such as hypochlorites : Periodate can exist in

490-476: The enzyme is flexible. Phase-transfer catalysts for anionic reactants are often quaternary ammonium salts . Commercially important catalysts include benzyltriethylammonium chloride, methyltricaprylammonium chloride and methyltributylammonium chloride. Organic phosphonium salts are also used, e.g., hexadecyltributylphosphonium bromide. The phosphonium salts tolerate higher temperatures, but are unstable toward base, degrading to phosphine oxide . For example,

525-410: The nucleophilic substitution reaction of an aqueous sodium cyanide solution with an ethereal solution of 1-bromooctane does not readily occur. The 1-bromooctane is poorly soluble in the aqueous cyanide solution, and the sodium cyanide does not dissolve well in the ether. Upon the addition of small amounts of hexadecyltributylphosphonium bromide, a rapid reaction ensues to give nonyl nitrile: By

560-421: The deflection of projectiles from firearms (see Magnus effect ). From 1861 onwards he devoted much attention to the question of diathermancy in gases and vapours, especially to the behaviour in this respect of dry and moist air, and to the thermal effects produced by the condensation of moisture on solid surfaces. Magnus was an experimenter, not a theoretician. His great reputation led to his being entrusted by

595-522: The diminution in density produced in garnet and vesuvianite by melting (1831). Subjects on which he published research after 1833 include: the absorption of gases in blood (1837–1845); the expansion of gases by heat (1841–1844); the vapour pressures of water and various solutions (1844–1854); thermoelectricity (1851); electrolysis of metallic salts in solution (1857); electromagnetic induction of currents (1858–1861); absorption and conduction of heat in gases (1860s); polarization of heat (1866–1868); and

630-459: The external surface was partly covered with alkylsilane , called phase-boundary catalyst was prepared in two steps. First, titanium dioxide made from titanium isopropoxide was impregnated into NaY zeolite powder to give sample W-Ti-NaY. In the second step, alkysilane from n-octadecyltrichlorosilane (OTS) was impregnated into the W-Ti-NaY powder containing water. Due to the hydrophilicity of

665-462: The government with several missions; e.g. in 1865 he represented Prussia in the conference called at Frankfurt am Main to introduce a uniform metric system of weights and measures into Germany. He married in 1840 Bertha Humblot, of a French Huguenot family settled in Berlin, by whom he left a son and two daughters. Phase transfer catalyst In chemistry , a phase-transfer catalyst or PTC

700-407: The history of physics who were beneficiaries of Magnus's laboratory in the 1840s include Rudolf Clausius , Hermann Helmholtz and Gustav Wiedemann . Magnus's laboratory, which he privately owned, was integrated into the University of Berlin later on. Magnus published 84 papers in research journals. His research output was continuous over his lifetime: the first memoir was published in 1825 when he

735-425: The name implies, one or more of the reactants are transported into a second phase which contains both reactants. Phase-boundary catalysis (PBC) is a type of heterogeneous catalytic system which facilitates the chemical reaction of a particular chemical component in an immiscible phase to react on a catalytic active site located at a phase boundary . The chemical component is soluble in one phase but insoluble in

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770-416: The other. The catalyst for PBC has been designed in which the external part of the zeolite is hydrophobic , internally it is usually hydrophilic , notwithstanding to polar nature of some reactants. In this sense, the medium environment in this system is close to that of an enzyme . The major difference between this system and enzyme is lattice flexibility. The lattice of zeolite is rigid, whereas

805-441: The phase-transfer catalyst. The catalyst functions like a detergent for solubilizing the salts into the organic phase. Phase-transfer catalysis refers to the acceleration of the reaction upon the addition of the phase-transfer catalyst. By using a PTC process, one can achieve faster reactions, obtain higher conversions or yields , make fewer byproducts, eliminate the need for expensive or dangerous solvents that will dissolve all

840-475: The presence of strong acid catalyst, like H 2 SO 4 or HNO 3 epoxides are also converted into aldehyde or ketones or dicarbonyl compounds. Alkenes can also be oxidised and cleaved in the Lemieux–Johnson oxidation . This uses a catalytic loading of osmium tetroxide which is regenerated in situ by the periodate. The overall process is equivalent to that of ozonolysis . Cleavage reactions proceed via

875-446: The quaternary phosphonium cation, cyanide ions are "ferried" from the aqueous phase into the organic phase. Subsequent work demonstrated that many such reactions can be performed rapidly at around room temperature using catalysts such as tetra-n-butylammonium bromide and methyltrioctylammonium chloride in benzene/water systems. An alternative to the use of "quat salts" is to convert alkali metal cations into hydrophobic cations. In

910-439: The reactants in one phase, eliminate the need for expensive raw materials and/or minimize waste problems. Phase-transfer catalysts are especially useful in green chemistry —by allowing the use of water, the need for organic solvents is reduced. Contrary to common perception, PTC is not limited to systems with hydrophilic and hydrophobic reactants. PTC is sometimes employed in liquid/solid and liquid/gas reactions. As

945-417: The research lab, crown ethers are used for this purpose. Polyethylene glycols are more commonly used in practical applications. These ligands encapsulate alkali metal cations (typically Na and K ), affording large lipophilic cations. These polyethers have a hydrophilic "interiors" containing the ion and a hydrophobic exterior. Chiral phase-transfer catalysts have also been demonstrated. PTC

980-488: The substrate, an aqueous liquid phase containing most of the substrate in aqueous phase and the solid catalyst. In case of conventional catalytic system; In some systems, without vigorous stirring, no reactivity of the catalyst is observed in conventional catalytic system. Stirring and mass transfer from the organic to the aqueous phase and vice versa are required for conventional catalytic system. Conversely, in PBC, stirring

1015-443: The w-Ti-NaY surface, addition of a small amount of water led to aggregation owing to the capillary force of water between particles. Under these conditions, it is expected that only the outer surface of aggregates, in contact with the organic phase can be modified with OTS, and indeed almost all of the particles were located at the phase boundary when added to an immiscible water–organic solvent (W/O) mixture. The partly modified sample

1050-477: Was a German experimental scientist. His training was mostly in chemistry but his later research was mostly in physics. He spent the great bulk of his career at the University of Berlin , where he is remembered for his laboratory teaching as much as for his original research. He did not use his first given name, and was known throughout his life as Gustav Magnus. Magnus was born in Berlin to a Jewish family, his father

1085-453: Was a personal friend of Mitscherlich). That was followed by a year in Paris at the laboratory of Joseph Louis Gay-Lussac and Louis Jacques Thénard . Therefore, he had a first-rate education in experimental science when in 1831 he was appointed lecturer in physics and technology at the University of Berlin. In 1834 he became assistant professor, and in 1845 was appointed full professor, and later he

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1120-833: Was also used to determine the structure of monosaccharides. Periodate cleavage may be performed on an industrial scale to form dialdehyde starch which has uses in paper production . Periodates are powerful oxidising agents . They can oxidise catechol to 1,2-benzoquinone and hydroquinone to 1,4-benzoquinone . Sulfides can be effectively oxidised to sulfoxides . Periodates are sufficiently powerful to generate other strong inorganic oxidisers such as permanganate , osmium tetroxide and ruthenium tetroxide . Periodates are highly selective etchants for certain ruthenium -based oxides. Several staining agents use in microscopy are based around periodate (e.g. periodic acid–Schiff stain and Jones' stain ). Periodates have also been used as oxidising agents for use in pyrotechnics . In 2013

1155-461: Was elected the dean of the faculty. As a teacher at the University of Berlin his success was rapid and extraordinary. His lucid style and the perfection of his experimental demonstrations drew to his lectures a crowd of enthusiastic scholars, on whom he impressed the importance of applied science; and he further found time to hold weekly colloquies on physical questions at his house with a small circle of young students. Furthermore, Magnus's laboratory

1190-510: Was one of the best equipped in the world during the years when he was professor in Berlin, and especially during the decade of the 1840s. This was as a result of his inherited money, his focus on experiment in chemistry and physics, his knowledge of the state-of-the-art methods, the scarcity of other laboratories in Europe at the time, and finally the high value he placed on facilitating the researches of up-and-coming young scientists. Well-known names in

1225-487: Was still a student, and the last appeared shortly after his death in 1870. From 1825 to 1833 he was occupied mainly with chemical researches. These resulted in the discovery of the first of the platino - ammonium class of compounds (see Magnus's green salt ). He was first to identify the three sulfonic acids sulphovinic acid , ethionic acid and isethionic acid and their salts; and, in cooperation with CF Ammermüller, of per-iodic acid and its salts. He also reported on

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