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Periodic Acid
Periodic acid ( ) is the highest oxoacid of iodine, in which the iodine exists in oxidation state +7. Like all periodates it can exist in two forms: orthoperiodic acid, with the chemical formula , and metaperiodic acid, which has the formula . Periodic acid was discovered by Heinrich Gustav Magnus and C. F. Ammermüller in 1833. Synthesis Modern industrial scale production involves the oxidation of a solution of sodium iodate under alkaline conditions, either electrochemically on a anode, or by treatment with chlorine: : (counter ions omitted for clarity) ''E''° = -1.6 V : Orthoperiodic acid can be dehydrated to give metaperiodic acid by heating to 100 °C under reduced pressure. : Further heating to around 150 °C gives iodine pentoxide () rather than the expected anhydride ''diiodine heptoxide'' (). Metaperiodic acid can also be prepared from various orthoperiodates by treatment with dilute nitric acid. Properties Orthoperiodic acid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Periodate
Periodate is an anion composed of iodine and oxygen. It is one of a number of oxyanions of iodine and is the highest in the series, with iodine existing in oxidation state +7. Unlike other perhalogenates, such as perchlorate, it can exist in two forms: metaperiodate and orthoperiodate . In this regard it is comparable to the tellurate ion from the adjacent Group (periodic table), group. It can combine with a number of counter ions to form periodates, which may also be regarded as the salts of periodic acid. Periodates were discovered by Heinrich Gustav Magnus and C. F. Ammermüller; who first synthesised periodic acid in 1833. Synthesis Classically, periodate was most commonly produced in the form of sodium hydrogen periodate (). 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: :\overset + Cl2 + 4 NaOH -> Na3H2IO6 + 2NaCl + H2O :Na ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lead Dioxide
Lead(IV) oxide is the inorganic compound with the formula PbO2. It is an oxide where lead is in an oxidation state of +4. It is a dark-brown solid which is insoluble in water. It exists in two crystalline forms. It has several important applications in electrochemistry, in particular as the positive plate of lead acid batteries. Properties Physical Lead dioxide has two major polymorphs, alpha and beta, which occur naturally as rare minerals scrutinyite and plattnerite, respectively. Whereas the beta form had been identified in 1845, α-PbO2 was first identified in 1946 and found as a naturally occurring mineral 1988. The alpha form has orthorhombic symmetry, space group Pbcn (No. 60), Pearson symbol ''oP''12, lattice constants ''a'' = 0.497 nm, ''b'' = 0.596 nm, ''c'' = 0.544 nm, ''Z'' = 4 (four formula units per unit cell). The lead atoms are six-coordinate. The symmetry of the beta form is tetragonal, space group P42/mnm (No. 136), Pearson symbol ''tP''6, la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diol
A diol is a chemical compound containing two hydroxyl groups ( groups). An aliphatic diol is also called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. The most common industrial diol is ethylene glycol. Examples of diols in which the hydroxyl functional groups are more widely separated include 1,4-butanediol and propylene-1,3-diol, or beta propylene glycol, . Synthesis of classes of diols Geminal diols A geminal diol has two hydroxyl groups bonded to the same atom. These species arise by hydration of the carbonyl compounds. The hydration is usually unfavorable, but a notable exception is formaldehyde which, in water, exists in equilibrium with methanediol H2C(OH)2. Another example is (F3C)2C(OH)2, the hydrated form of hexafluoroacetone. Many gem-diols undergo further condensation to give dimeric and oligomeric derivatives. This reaction applies to glyoxal and related aldehydes. Vicinal diols In a vicinal diol, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vicinal (chemistry)
In chemistry the descriptor vicinal (from Latin ''vicinus'' = neighbor), abbreviated ''vic'', describes any two functional groups bonded to two adjacent carbon atoms (i.e., in a 1,2-relationship). Relation of atoms in a molecule For example, the molecule 2,3-dibromobutane carries two vicinal bromine atoms and 1,3-dibromobutane does not. Mostly, the use of the term vicinal is restricted to two ''identical'' functional groups. Likewise in a ''gem-''dibromide the prefix ''gem'', an abbreviation of geminal, signals that both bromine atoms are bonded to the ''same'' atom (i.e., in a 1,1-relationship). For example, 1,1-dibromobutane is geminal. While comparatively less common, the term hominal has been suggested as a descriptor for groups in a 1,3-relationship. Like other such descriptors as syn, anti, exo or endo, the description ''vicinal'' helps explain how different parts of a molecule are related to each other either structurally or spatially. The vicinal adjective is somet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Group
In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it unchanged. In three dimensions, space groups are classified into 219 distinct types, or 230 types if chiral copies are considered distinct. Space groups are discrete cocompact groups of isometries of an oriented Euclidean space in any number of dimensions. In dimensions other than 3, they are sometimes called Bieberbach groups. In crystallography, space groups are also called the crystallographic or Fedorov groups, and represent a description of the symmetry of the crystal. A definitive source regarding 3-dimensional space groups is the ''International Tables for Crystallography'' . History Space groups in 2 dimensions are the 17 wallpaper groups which have been known for several centuries, though the proof that the list was complete was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic system. They form a parallelogram prism. Hence two pairs of vectors are perpendicular (meet at right angles), while the third pair makes an angle other than 90°. Bravais lattices Two monoclinic Bravais lattices exist: the primitive monoclinic and the base-centered monoclinic. For the base-centered monoclinic lattice, the primitive cell has the shape of an oblique rhombic prism;See , row mC, column Primitive, where the cell parameters are given as a1 = a2, α = β it can be constructed because the two-dimensional centered rectangular base layer can also be described with primitive rhombic axes. Note that the length a of the primitive cell below equals \frac \sqrt of the conventional cell above. Crystal classes The table below org ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Periodate
Sodium periodate is an inorganic salt, composed of a sodium cation and the periodate anion. It may also be regarded as the sodium salt of periodic acid. Like many periodates, it can exist in two different forms: sodium ''meta''periodate (formula NaIO4) and sodium ''ortho''periodate (normally Na2H3IO6, but sometimes the fully reacted salt Na5IO6). Both salts are useful oxidising agents. Preparation Classically, periodate was most commonly produced in the form of sodium hydrogen periodate (). 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: :\overset + Cl2 + 4 NaOH -> Na3H2IO6 + 2NaCl + H2O :NaI + 4 Br2 + 10 NaOH -> Na3H2IO6 + 8 NaBr + 4 H2O Modern industrial scale production involves the electrochemical oxidation of iodates, on a lead dioxide () anode, with the following standard electrode potential: :H5IO6 + H+ + 2e- -> IO3- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acid Dissociation Constant
In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction :HA A^- + H^+ known as dissociation in the context of acid–base reactions. The chemical species HA is an acid that dissociates into , the conjugate base of the acid and a hydrogen ion, . The system is said to be in equilibrium when the concentrations of its components will not change over time, because both forward and backward reactions are occurring at the same rate. The dissociation constant is defined by :K_\text = \mathrm, or :\mathrmK_\ce = - \log_ K_\text = \log_\frac where quantities in square brackets represent the concentrations of the species at equilibrium. Theoretical background The acid dissociation constant for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the p''K''a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitric Acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% , it is referred to as ''fuming nitric acid''. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%. Nitric acid is the primary reagent used for nitration – the addition of a nitro group, typically to an organic molecule. While some resulting nitro compounds are shock- and thermally-sensitive explosives, a few are stable enough to be used in munitions and demolition, while others are still more stable and used as pigments in inks and dyes. Nitric acid is also commonly used as a strong oxidizing age ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anhydride
An organic acid anhydride is an acid anhydride that is an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O))2O. Symmetrical acid anhydrides of this type are named by replacing the word ''acid'' in the name of the parent carboxylic acid by the word ''anhydride''. Thus, (CH3CO)2O is called ''acetic anhydride.'' Mixed (or unsymmetrical) acid anhydrides, such as acetic formic anhydride (see below), are known, whereby reaction occurs between two different carboxylic acids. Nomenclature of unsymmetrical acid anhydrides list the names of both of the reacted carboxylic acids before the word "anhydride" (for example, the dehydration reaction between benzoic acid and propanoic acid would yield "benzoic propanoic anhydride"). One or both acyl groups of an acid anhydride may also be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iodine Pentoxide
Iodine pentoxide is the chemical compound with the formula I2O5. This iodine oxide is the anhydride of iodic acid, and the only stable oxide of iodine. It is produced by dehydrating iodic acid at 200 °C in a stream of dry air: :2HIO3 → I2O5 + H2O Structure I2O5 is bent with an I–O–I angle of 139.2°, but the molecule has no mirror plane so its symmetry is C2 rather than C2v. The terminal I–O distances are around 1.80 Å and the bridging I–O distances are around 1.95 Å. Reactions Iodine pentoxide easily oxidises carbon monoxide to carbon dioxide at room temperature: :5 CO + I2O5 → I2 + 5 CO2 This reaction can be used to analyze the concentration of CO in a gaseous sample. I2O5 forms iodyl salts, O2+ with SO3 and S2O6F2, but iodosyl salts, O+ with concentrated sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Electrode Potential
In electrochemistry, standard electrode potential E^\ominus, or E^\ominus_, is a measure of the reducing power of any element or compound. The IUPAC "Gold Book" defines it as: ''"the value of the standard emf (electromotive force) of a cell in which molecular hydrogen under standard pressure is oxidized to solvated protons at the left-hand electrode"''. Background The basis for an electrochemical cell, such as the galvanic cell, is always a redox reaction which can be broken down into two half-reactions: oxidation at anode (loss of electron) and reduction at cathode (gain of electron). Electricity is produced due to the difference of electric potential between the individual potentials of the two metal electrodes with respect to the electrolyte. Although the overall potential of a cell can be measured, there is no simple way to accurately measure the electrode/electrolyte potentials in isolation. The electric potential also varies with temperature, concentration and pressur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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