Showing papers on "Iodide published in 1983"

Cleavage of Ethers

Abstract: The scope and limitations of reagents for the cleavage of ethers are discussed. The reagents are conveniently classified in the five main headings. Selectivity patterns of some of the reagents are discussed in cases where sufficient data has been given in the literature. 1. Introduction 2. Acidic Reagents 2.1. Bronsted Acids 2.2. Lewis Acids 3. Basic Reagents 3.1. Alkali Hydroxides 3.2. Alkali Alkoxides 3.3. Alkali Amides 3.4. Alkali Metals 3.5. Organo-Alkali Metal Compounds 3.6. Sodium Cyanide/Dimethyl Sulfoxide 3.7. Sodium Ethanethiolate 3.8. Sodium Thiocresolate 3.9. Lithium Iodide 3.10. Sodium Benzeneselenolate 4. Miscellaneous Reagents 4.1. Iodotrimethylsilane 4.2. Iodotrichlorosilane 4.3. Dichloroiodomethylsilane 4.4. Bromotrimethylsilane 4.5. Alkylthiotrimethylsilanes 4.6. Ethanethiol or Ethanedithiol/Boron Trifluoride Etherate 4.7. Aluminium Halide/Thiol Systems 4.8. Acetyl Iodide and Pivaloyl Iodide 4.9. Diiodomethyl Ether/Hydrogen Iodide 5. Reductive Cleavage of Ethers 5.1. Lithium Tris[t-butoxy]aluminium Hydride/Triethylborane Complex 5.2. Hydrogenolysis 6. Oxidative Cleavage of Ethers 6.1. Ceric Ammonium Nitrate 6.2. Silver Oxide 6.3. Dichlorodicyanoquinone 6.4. Tris[p-bromophenyl]ammonium Hexachloroantimonate 7. Photochemical Cleavage of Ethers 8. Selectivity in Ether Cleavage 8.1. Stereoelectronic Characteristics of the Ether-Cleaving Agent 8.2. Structural Features of the Groups Cleaved 8.3. Molecular Environment of the C-O Bond not Undergoing Cleavage 9. Addendum

Synthesis of the radical scavenger 1,1,3,3-Tetramethylisoindolin-2-yloxyl

Abstract: A versatile free-radical trapping agent, 1,1,3,3-tetramethylisoindolin-2-yloxyl, has been prepared from N-benzylphthalimide by reaction with 'methylmagnesium iodide' in refluxing toluene followed by hydrogenolysis and oxidation. The Grignard reaction gives 2-benzyl-1,1,3,3-tetramethylisoindoline along with a small proportion of an unexpected by-product, 2-benzyl-1-ethyl-1,3,3-trimethyliso-indoline.

Polarization of thyroid cells in culture: evidence for the basolateral localization of the iodide "pump" and of the thyroid-stimulating hormone receptor-adenyl cyclase complex.

Abstract: When cultured in collagen gel-coated dishes, thyroid cells organized into polarized monolayers. The basal poles of the cells were in contact with the collagen gel, whereas the apical surfaces were facing the culture medium. Under these culture conditions, thyroid cells do not concentrate iodide nor respond to acute stimulation by thyroid-stimulating hormone (TSH). To allow the free access of medium components to the basal poles, the gel was detached from the plastic dish and allowed to float in the culture medium. After release of the gel, the iodide concentration and acute response to TSH stimulation were restored. Increased cAMP levels, iodide efflux, and formation of apical pseudopods were observed. When the thyroid cells are cultured on collagen-coated Millipore filters glued to glass rings, the cell layer separates the medium in contact with the apical domain of the plasma membrane (inside the ring) from that bathing the basolateral domain (outside the ring). Iodide present in the basal medium was concentrated in the cells, whereas no transport was observed when iodide was added to the luminal side. Similarly, an acute effect of TSH was observed only when the hormone was added to the basal medium. These results show that the iodide concentration mechanism and the TSH receptor-adenylate cyclase complex are present only on the basolateral domain of thyroid cell plasma membranes.

Chemical mechanism of the Gram stain and synthesis of a new electron-opaque marker for electron microscopy which replaces the iodine mordant of the stain.

Abstract: Crystal violet (hexamethyl-para-rosaniline chloride) interacts with aqueous KI-I2 during the Gram stain via a simple metathetical anion exchange to produce a chemical precipitate. There is an apparent 1:1 stoichiometry between anion (I-) and cation (hexamethyl-para-rosaniline+) during the reaction and, since the small chloride anion is replaced by the bulkier iodide, the complex formed becomes insoluble in water. It is this same precipitate which forms in the cellular substance of bacteria (both gram-positive and gram-negative types) and which initiates the Gram reaction. Potassium trichloro(eta 2-ethylene)-platinum(II), as an electronopaque marker for electron microscopy, was chemically synthesized, and it produced an anion in aqueous solution which was compatible with crystal violet for the Gram stain. It interacted with crystal violet in a similar manner as iodide to produce an insoluble complex which was chemically and physically analogous to the dye-iodide precipitate. This platinum anion therefore allows the Gram staining mechanism to be followed by electron microscopy.

Congenital Goiter with Defective Iodide Transport

Abstract: THE TWENTY-TWO known cases of congenital goiter, with or without cretinism, that are due to defective iodide concentrating ability have been compared. The defect may be total or partial, sometimes becomes clinically manifest long after the neonatal period, shows male predominance, and frequently occurs without evidence of consanguinity or partial defects in the parents. The degree of clinical or laboratory hypothyroidism may vary but radioiodide uptake is low or absent. The diagnosis is based on the failure to concentrate iodide in salivary or gastric secretions on the one hand, and the attainment of the euthyroid state by iodide replacement alone. Limited evidence suggests that the defect is due to the absence or malfunction of the iodide carrier. The ion exchange basis of thyroidal anion selectivity dictates certain properties for the hypothetical iodide carrier which are dicussed. Introduction The concept that iodide transport is an independent step in the biosynthesis of the thyroid hormones was first...

Iodide enhances IgG synthesis by human peripheral blood lymphocytes in vitro

Abstract: Several studies have suggested that iodide may increase thyroiditis and autoantibody synthesis. We have investigated the effect of iodide in vitro at physiologically relevant concentrations on immunoglobulin synthesis by normal human peripheral blood lymphocytes stimulated with pokeweed mitogen. Both the number of cells which synthesised IgG and the amount of IgG released into the culture supernatant increased significantly after culture in a medium with added iodide compared to a medium with added chloride. No effect of increasing concentrations of the added iodide from 10(-3) mM to 10 mM was observed. These findings suggest that iodides may have a role in enhancing antibody synthesis which may be important when programmes of iodide supplementation are introduced into areas which are deficient.

Preparation of Aryltributyltin Having Electron-withdrawing Group by Palladium Catalyzed Reaction of Hexabutylditin with Aryl Iodide

Abstract: Nitro-, acyl-, and cyanophenyltributyltin can be prepared by the reaction of hexabutylditin with the corresponding aryl iodide in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium.

Mossbauer Spectroscopic Study of Iodine-Doped Polyacetylene

Abstract: The Mossbauer spectroscopy has been applied to iodine-doped polyacetylene employing 129 I. It is found that the polymer films contain I - , I 3 - and I 5 - with symmetrical charge population, where the content of each iodide anion depends on the doping level. Under dynamic evacuation, it is elucidated that I 5 - converts to I 3 - by the elimination of I 2 from I 5 - . The variation of electrical conductivity in iodine-doped polyacetylene is discussed with the mechanism of charge transfer from the polymer and with the mutual conversion of iodide anions.

Selective demethylation of aliphatic methyl ether in the presence of aromatic methyl ether with the aluminum chloride-sodium iodide-acetonitrile system.

Abstract: A combination system of aluminum chloride-sodium iodide-acetonitrile effects aselective demethylation of aliphatic methyl ethers in the presence of aromatic methyl ether.

A modification of thiocholine-ferricyanide method of Karnovsky and Roots for localization of acetylcholinesterase activity without interference by Koelle's copper thiocholine iodide precipitate.

Abstract: In the original Karnovsky and Roots' method for the localization of acetylcholinesterase (AChE), thiocholine reduces the ferricyanide and cupric ions of this medium competitively, giving simultaneously cupric (Koelle's precipitate) as histochemical products. We modified the method in order to promote the true Karnovsky's reaction, and to slow down the secondary Koelle's reaction by increasing the concentration of the ferricyanide ion from 0.5 mM to 5.0 mM and by decreasing the concentration of the cupric ion from 3.0 mM to 2.5 mM. The cupric ion, complexed with 5 mM sodium citrate in the original method, was further stabilized by the use of 0.1 M citrate buffer in order to prevent the interaction of cupric ion with increased ferricyanide. In order to suppress completely the residual Koelle's precipitate, we used acetylthiocholine chloride as a substrate, instead of acetylthiocholine iodide. The chloride salt of cuprous thiocholine is soluble, contrary to the iodide salt. In addition, the pH of the medium was lowered from 6.0 to 5.0 to avoid artefactual nuclear staining, appearing at a pH beyond 5.5. In this modified medium, Karnovsky's cupric ferrocyanide becomes the sole precipitate at the enzymatic site and this provides fine localization of acetylcholinesterase activity.

Cation exchange resin (hydrogen form) assisted decomposition of 1-aryl-3,3-dialkyltriazenes. A mild and efficient method for the synthesis of aryl iodides

Abstract: Reported is a regioselective synthesis of aryl iodides, a process that is suitable for preparing isotopically labelled material. The treatment of several triazenes with a well-dried sample of sodium iodide and a sulfonic cation exchange resin (H/sup +/ form, Bio-Rad AG AG 50W-X12) in dry acetonitrile at 75/sup 0/C produced excellent yields of the corresponding aryl iodides. A high probability exists that the acid resin plays a striking role in these reactions, by protonating and consequently immobilizing the basic aromatic triazene on the resin surface facilitating the nucleophilic attack by the iodide ions.

Influence of chemical forms on iodine uptake by plant.

Abstract: Uptake of iodide and iodate by komatsuna, Brassica Rapa var. pervidis, was studied using culture solution containing radioiodine as a tracer. After 24 hours'' exposure, accumulation of iodide in the plant was several times higher than that of iodate. The concentrations of both iodide and iodate in roots were much higher than those in shoots. It was estimated that high accumulation of iodide in roots was due to the adsorption of the element on the root surface. The plant of the earlier growth stage absorbed iodide selectively from the solution. On the contrary that of the older growth stage, more than 40 days after seeding, showed less absorption of the element. Influence of stable iodine content on the uptake of radioiodine was also examined. The transfer rate of radioactive iodide to roots decreased remarkably with increasing amount of stable iodide in the culture solution, whereas that to shoots remained relatively constant indicating that the element content in shoots increased almost proportionally with the increasing concentration of stable iodine in the solution. A significant amount of iodate in the culture solution was transformed to iodide in the presence of plant. The dominant chemical form of iodine in the plant was thought to be iodide.

(β-Cyclodextrin)2·KI7·9 H2O. Spatial fitting of a polyiodide chain to a given matrix

Abstract: α-Cyclodextrin, a torus shaped molecule with a 5 A wide central cavity, forms a number of deep green, blue and black crystals when complexed with iodine/metal iodide. In contrast, β-cyclodextrin, having a 6 A cavity produces only one type of reddish-brown crystal, no matter what metal iodide is used. The complex (β-cyclodextrin)2 ·KI7·9H2O displays space groupP21 (pseudo-C2) with cell constantsa=19.609(5),b=24.513(7),c=15.795(6)A, β=109.50(2)°,Z=4. The crystal structure was solved inC2 on the basis of 3022 absorption corrected CuKα (Ni-filter) X-ray intensities and refined by full matrix least squares toR=17%. This relatively highR-factor is due to many weak reflections (pseudo-C2) and considerable disorder exhibited by water and iodine. In the complex, β-cyclodextrin adopts a ‘round’ shape with O(2)...O(3) interglucose hydrogen bonds formed and all O(6) hydroxyls pointing away from the cavity. Two molecules are arranged head-to-head to produce a dimer, and dimers are stacked such that a slightly zigzagged cylinder with a 6 A-wide cavity is formed. In the cavity described by each dimer, an I 7 − ion composed of I2·I 3 − ·I2 units is located, with I2 and I 3 − perpendicular to each other. K+ ions and 9 H2O molecules are found in interstices between the β-cyclodextrin cylinders. This zigzag polyiodide contrasts with the linear form observed in the 5 A wide α-cyclodextrin channels. It explains differences in color of the crystals and suggests that β-cyclodextrin polyiodide is not a good model for blue starch-iodine.

Process for producing ethanol

Abstract: A process for producing ethanol which comprises reacting methanol, carbon monoxide and hydrogen in the presence of (a) a catalyst comprising cobalt or a cobalt compound and an alkyl phosphine as an effective component and (b) a co-catalyst comprising hydrochloric acid and in the absence of an iodide is disclosed. According to the present invention, formation of by-products becomes less and selectivity to realizable ethanol becomes higher.