Chromium sulfate refers to inorganic compounds with the chemical formula CrSO4·n H2O. Several closely related hydrated salts are known, the pentahydrate is a blue solid that dissolves readily in water. Solutions of chromium are easily oxidized by air to Cr species, solutions of Cr are used as specialized reducing agents of value in organic synthesis. In aqueous solutions chromium sulfate forms metal aquo complexes, presumably with six water ligands, the structures of the crystalline salts are similar to the corresponding hydrates of copper sulfate, trihydrate and anhydrous derivatives of chromous sulfate are known. In all of these compounds, the Cr centre adopts octahedral coordination geometry, being coordinated to six oxygen centers provided by a combination of water and sulfate ligands
Pyridinium chlorochromate is a yellow-orange salt with the formula. It is a reagent in organic synthesis used primarily for oxidation of alcohols to form carbonyls, a variety of related compounds are known with similar reactivity. Although no longer used, PCC offers the advantage of the selective oxidation of alcohols to aldehydes or ketones. PCC consists of a cation, +, and a tetrahedral chlorochromate anion. Related salts are known, such as 1-butylpyridinium chlorochromate. PCC is used as an oxidant, in particular, it has proven to be highly effective in oxidizing primary and secondary alcohols to aldehydes and ketones, respectively. Unlike with the related Jones reagent, rarely does over-oxidation occur to form carboxylic acids, a typical PCC oxidation involves addition of an alcohol to a suspension of PCC in dichloromethane. Other common oxidants usually lead to dehydration because such alcohols cannot be oxidized directly, PCC converts suitable unsaturated alcohols and aldehydes to cyclohexenones.
This pathway, an oxidative cationic cyclization, is illustrated by the conversion of -citronellol to -pulegone, PCC effects allylic oxidations, for example, in conversion of dihydrofurans to furanones. One disadvantage to the use of PCC is its toxicity, which it shares with other hexavalent chromium compounds, oxidation with chromium-amine complexes Tojo, G. Fernández, M. Tojo, G. ed. Oxidation of Alcohols to Aldehydes and Ketones, A Guide to Current Common Practice, IARC Monographs Supplement 7, Chromium and Chromium Compounds History of PCC National Pollutant Inventory, Chromium Compounds Fact Sheets
Bischromium is the organometallic compound with the formula Cr2. The compound played an important role in the development of compounds in organometallic chemistry and is the prototypical complex containing two arene ligands. The substance is air sensitive and its synthesis requires air-free techniques and it was first prepared by Hafner and Fischer by the reaction of CrCl3, and benzene, in the presence of AlCl3. This so-called reductive Friedel-Crafts method was pioneered by E. O. Fischer, the product of the reaction was yellow +, which was reduced to the neutral complex. In this way, the complex can be prepared. Compounds closely related to + had been prepared many years before Fischers work by Franz Hein by the reaction of phenylmagnesium bromide, Heins reaction affords cationic sandwich complexes containing bi- and terphenyl, which baffled chemists until the breakthrough by Fischer and Hafner. Fischer and Seus soon prepared Heins + by a route, thus confirming that Hein had unknowingly discovered sandwich complexes.
Illustrating the rapid pace of research, the same issue of Chem. Ber. describes the Mo complex, the compound reacts with carboxylic acids to give chromium carboxylates, such as chromium acetate, which have interesting structures. The compound finds limited use in organic synthesis
Chromium tricarbonyl is an organometallic compound with the formula Cr3. This yellow crystalline solid compound is soluble in nonpolar organic solvents. The molecule adopts a geometry known as “piano stool” because of the arrangement of the aryl group. Tricarbonylchromium was first reported in 1957 by Fischer and Öfele, who prepared the compound by the carbonylation of bischromium and they obtained mainly chromium carbonyl and traces of Cr3. The synthesis was optimized through the reaction of Cr6 and Cr2 and it is more acidic, undergoing lithiation upon treatment with n-butyllithium. The product alkene results from 1, 4-addition of hydrogen, the complex does not hydrogenate isolated double bonds
Chromium chloride describes any of several compounds of with the formula CrCl3x, where x can be 0,5, and 6. The anhydrous compound with the formula CrCl3 is a violet solid, the most common form of the trichloride is the dark green hexahydrate, CrCl3. 6H2O. Chromium chloride finds uses as catalysts and as precursors to dyes for wool, anhydrous chromium chloride adopts the YCl3 structure, with Cr3+ occupying two thirds of the octahedral interstices in alternating layers of a pseudo-cubic close packed lattice of Cl− ions. The absence of cations in alternate layers leads to weak bonding between adjacent layers, for this reason, crystals of CrCl3 cleave easily along the planes between layers, which results in the flaky appearance of samples of chromium chloride. The different forms exist both as solids, and in aqueous solutions, several members are known of the series of z+. The main hexahydrate can be precisely described as Cl•2H2O. It consists of the cation trans-+ and additional molecules of water, two other hydrates are known, pale green Cl2•H2O and violet Cl3.
Similar behaviour occurs with other chromium compounds, in laboratory the hydrates are usually prepared by dissolving the chromium metal or chromium oxide in hydrochloric acid. Slow reaction rates are common with chromium complexes, the low reactivity of the d3 Cr3+ ion can be explained using crystal field theory. One way of opening CrCl3 up to substitution in solution is to even a trace amount to CrCl2. This chromium compound undergoes substitution easily, and it can exchange electrons with CrCl3 via a chloride bridge, with the presence of some chromium, solid CrCl3 dissolves rapidly in water. Similarly, ligand substitution reactions of solutions of + are accelerated by chromium catalysts, CrCl3 is a Lewis acid, classified as hard according to the Hard-Soft Acid-Base theory. It forms a variety of adducts of the z, where L is a Lewis base. For example, it reacts with pyridine to form an adduct, CrCl3 +3 C5H5N → CrCl33 Treatment with trimethylsilylchloride in THF gives the anhydrous THF complex, CrCl3.
One niche use of CrCl3 in organic synthesis is for the in situ preparation of chromium chloride, the reaction is usually performed using two moles of CrCl3 per mole of lithium aluminium hydride, although if aqueous acidic conditions are appropriate zinc and hydrochloric acid may be sufficient. Chromium chloride has used as a Lewis acid in organic reactions. A number of chromium-containing dyes are used commercially for wool, typical dyes are triarylmethanes consisting of ortho-hydroxylbenzoic acid derivatives. Although trivalent chromium is far less poisonous than hexavalent, chromium salts are considered toxic
Chlorine azide is an inorganic compound that was discovered in 1908 by Friedrich Raschig. Concentrated ClN3 is notoriously unstable and may spontaneously detonate at any temperature, chlorine azide is prepared by passing chlorine gas over silver azide, or by an addition of acetic acid to a solution of sodium hypochlorite and sodium azide. When treated with ammonia it is conceivable that one or more of the three possible azinamines, NH2N3, NH2, and N3 may be formed and it may explode, sometimes even without apparent provocation, it is thus too sensitive to be used commercially unless first diluted in solution. Chlorine azide reacts explosively with 1, 3-butadiene, ethene, propane, silver azide, on contact with acid, chlorine azide decomposes, evolving toxic and corrosive hydrogen chloride gas. Its shipment is strictly regulated by the US Department of Transportation
The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. This kind of acid may be used as a cleaning mixture for glass. Chromic acid may refer to the species, H2CrO4 of which the trioxide is the anhydride. Chromic acid features chromium in a state of +6. It is a strong and corrosive oxidising agent, molecular chromic acid, H2CrO4, has much in common with sulfuric acid, H2SO4. Both are classified as acids, though only the first proton is lost easily. H2CrO4 ⇌ − + H+ The pKa for the equilibrium is not well characterized, reported values vary between about −0.8 to 1.6. The value at zero ionic strength is difficult to determine because half dissociation only occurs in acidic solution, at about pH0. A further complication is that the ion − has a tendency to dimerize, with the loss of a water molecule, to form the dichromate ion. Furthermore, the dichromate can be protonated, − ⇌ 2− + H+ pK =1.8 The pK value for this shows that it can be ignored at pH >4.
Loss of the second occurs in the pH range 4–8. Molecular chromic acid could in principle be made by adding chromium trioxide to water, CrO3 + H2O ⇌ H2CrO4 but in practice the reverse reaction occurs when molecular chromic acid is dehydrated. This is what happens when concentrated sulfuric acid is added to a dichromate solution, at first the colour changes from orange to red and deep red crystals of chromium trioxide precipitate from the mixture, without further colour change. The colours are due to LMCT transitions, Chromium trioxide is the anhydride of molecular chromic acid. It is a Lewis acid and can react with a Lewis base, dichromic acid, H2Cr2O7, is the fully protonated form of the dichromate ion and can be seen as the product of adding chromium trioxide to molecular chromic acid. 2− + 2H+ ⇌ H2Cr2O7 ⇌ H2CrO4 + CrO3 It is probably present in chromic acid cleaning mixtures along with the mixed chromosulfuric acid H2CrSO7, chromic acid is an intermediate in chromium plating, and is used in ceramic glazes, and colored glass.
Because a solution of acid in sulfuric acid is a powerful oxidizing agent, it can be used to clean laboratory glassware. This application has declined due to environmental concerns, the acid leaves trace amounts of paramagnetic chromic ions — Cr — that can interfere with certain applications, such as NMR spectroscopy
These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, the simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the numbers of each type of atom in a molecule. For example, the formula for glucose is CH2O, while its molecular formula is C6H12O6. This is possible if the relevant bonding is easy to show in one dimension, an example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. For reasons of structural complexity, there is no condensed chemical formula that specifies glucose, chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. A chemical formula identifies each constituent element by its chemical symbol, in empirical formulas, these proportions begin with a key element and assign numbers of atoms of the other elements in the compound, as ratios to the key element.
For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules. These types of formulas are known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the formula for glucose is C6H12O6 rather than the glucose empirical formula. However, except for very simple substances, molecular chemical formulas lack needed structural information, for simple molecules, a condensed formula is a type of chemical formula that may fully imply a correct structural formula.
For example, ethanol may be represented by the chemical formula CH3CH2OH
Chromium(VI) oxide peroxide
The generally yellow chromates or orange dichromates turn to dark blue as chromium peroxide is formed. Chromate or dichromate reacts with hydrogen peroxide and an acid to give chromium peroxide, crO42− +2 H2O2 +2 H+ → CrO5 +3 H2O After a few seconds, the chromium peroxide decomposes to turn green as chromium compounds are formed. In this way, the peroxide is dissolved in the immiscible organic solvent. In this condition it can be observed over a longer period. 2 CrO5 +7 H2O2 +6 H+ →2 Cr3+ +10 H2O +7 O2 This compound contains one oxo ligand, the etherate and pyridyl complexes of this compound have been found to be effective oxidants in organic chemistry. The structure of the complex has been determined crystallographically
Nitrogen trichloride, known as trichloramine, is the chemical compound with the formula NCl3. This yellow, pungent-smelling liquid is most commonly encountered as a byproduct of chemical reactions between ammonia-derivatives and chlorine, the compound is prepared by treatment of ammonium salts, such as ammonium nitrate with chlorine. Intermediates in this conversion include chloramine and dichloramine, NH2Cl and NHCl2, like ammonia, NCl3 is a pyramidal molecule. The N-Cl distances are 1.76 Å, and the Cl-N-Cl angles are 107°, dogs that ate bread made from treated flour suffered epileptic-like fits, the toxic agent was methionine sulfoximine. The chemistry of NCl3 has been well explored and it is moderately polar with a dipole moment of 0. The nitrogen center is basic but much less so than ammonia and it is hydrolyzed by hot water to release ammonia and hypochlorous acid. NCl3 +3 H2O → NH3 +3 HOCl NCl3 explodes to give N2 and this reaction is inhibited for dilute gases. Nitrogen trichloride can irritate mucous membranes—it is an agent, but has never been used as such.
The pure substance is an explosive, being sensitive to light, even moderate shock. Pierre Louis Dulong first prepared it in 1812, and lost two fingers and an eye in two explosions, in 1813, an NCl3 explosion blinded Sir Humphry Davy temporarily, inducing him to hire Michael Faraday as a co-worker. They were both injured in another NCl3 explosion shortly thereafter, list of food contamination incidents Jander, J. Recent Chemistry and Structure Investigation of Nitrogen Triiodide, Trichloride, kovacic, P. Lowery, M. K. Field, K. W. Chemistry of N-Bromamines and N-Chloramines. Hartl, H. Schöner, J. Jander, J. Schulz, zeitschrift für Anorganische und Allgemeine Chemie. Cazzoli, G. Favero, P. G. Dal Borgo, molecular Structure, Nuclear Quadrupole Coupling Constant and Dipole Moment of Nitrogen Trichloride from Microwave Spectroscopy. Fischer, J. Höhne, K. Jander, J. Untersuchungen an Stickstoff–Chlor-Verbindungen, V. Infrarot- und RAMAN-Spektren von Stickstofftrichlorid. Zeitschrift für Anorganische und Allgemeine Chemie, OSHA - Nitrogen trichloride Nitrogen Trichloride - Health References