Chromous chloride

Chromium(IJ) chloride, chromous chloride, CrCl2- White solid (Cr plus HCl gas) dissolving to give a blue solution. Forms hydrates, widely used as a reducing agent. 

Hydrogenation. Acetylene can be hydrogenated to ethylene and ethane. The reduction of acetylene occurs in an ammoniacal solution of chromous chloride (20) or in a solution of chromous salts in H2SO4 (20). The selective catalytic hydrogenation of acetylene to ethylene, which proceeds... 

Ghromium(II) Compounds. The Cr(II) salts of nonoxidizing mineral acids are prepared by the dissolution of pure electrolytic chromium metal ia a deoxygenated solution of the acid. It is also possible to prepare the simple hydrated salts by reduction of oxygen-free, aqueous Cr(III) solutions using Zn or Zn amalgam, or electrolyticaHy (2,7,12). These methods yield a solution of the blue Cr(H2 0)g cation. The isolated salts are hydrates that are isomorphous with and compounds. Examples are chromous sulfate heptahydrate [7789-05-17, CrSO 7H20, chromous chloride hexahydrate... 

Acetoxy-17a-hydroxy-5a-pregnane-3,l 1,20-trione (40) is brominated in acetic acid under equilibrating conditions to give a solution of the 2a,4a-di-bromo compound (41). This is reduced by chromous chloride without further treatment, to the 4a-bromo compound (42). The recrystallized bromo compound (42) is then dehydrobrominated via the semicarbazone (43) which is converted without isolation into cortisone acetate (44) by treatment with pyruvic acid ... 

It is not possible to use zinc for reductive debromination in the presence of (x-halo ketones and for transformations involving these intermediates, sodium iodide has been used. ° In some instances, e.g. 5,6-dihalo-3-ketones, iodide does not always give a completely halogen-free product, and zinc does not give clean debromination. The use of chromous chloride has proved advantageous in such cases and is the reagent of choice for vicinal dichlorides, which are inert to iodide ... 

The 10l -acetoxy group can be red actively removed with zinc and acetic acid or chromous chloride to give I9-norsteroids in high yield. Thermal elimination (boiling tetralin) of acetic acid from the crude 10)5-acetoxy-A -3-ketone or treatment with methanolic alkali leads to aromatization of ring A. Estrone alkyl ethers are formed from 10)5-acetoxy-19-nor-A -androstene-3,17-dione by treatment with alcohols and perchloric acid. Similar aromatizations are observed with 5,10-oxido, 5,10-dihydroxy, 5,10-halohydrins or 5,10-dihalo-3-ketones. ... 

Chrom-bleii n. lead chromate, -bleispat, m. (Min.) crocoite. -braun, n. chrome brown, -chlorid, n. chromic chloride. chromium(III) chloride, -chlorilr, n, chromous chloride, chromium(II) chloride, -druck, m. (Calico) chrome printing. 

Chromo-. chromous, chromium(II). -chlorid, n. chromous chloride, chromium(II) chloride. 

The groups R2N and Cl can be added directly to alkenes, allenes, conjugated dienes, and alkynes, by treatment with dialkyl-V-chloroamines and acids. " These are free-radical additions, with initial attack by the R2NH- radical ion. " N-Halo amides (RCONHX) add RCONH and X to double bonds under the influence of UV light or chromous chloride. " Amines add to allenes in the presence of a palladium catalyst. ... 

An unopened bottle of chromous chloride solution exploded after prolonged storage [1]. This was most likely caused by internal pressure of hydrogen developed by slow reduction of the solvent water by the powerfully reducing Cr(II) ion [2],... 

Several strategies closely related to the Peterson synthesis have been developed for diene and polyene generation. Angell, Parsons and coworkers reported a mild method for the diene installation on a carbonyl group using a y-bromoallylsilanc reagent in the presence of excess chromous chloride and a catalytic amount of nickel(II) chloride (equation 102)180. 

A nickel-chromium catalyst prepared from chromous chloride and (p-diphenylphos-phinopolystyrene)nickel dichloride mediates the ring-closure of the ene-allene 236 (R = H) to a mixture of 3.4 parts of 237 and 1 part of 238 (equation 120)121. An analogous reaction of the t-butyldimethylsilyl ether of 236 yields solely the (E)-isomer 237 (R = t-BuMeaSi). Cyclization of the ene-allene 239 affords the perhydroindane 240 in 72%... 

Chromous chloride hexahydrate, 6 531 Chromous sulfate heptahydrate, 6 531 Chromyl chloride, molecular formula, properties, and uses, 6 561t Chromyl compounds, 6 526, 536 Chromyl fluoride, 6 535 Chromyl perchlorate, anhydrous, 18 279 Chronic asthmatic bronchitis, effect on heart, 5 107... 

Divalent chromium salts show very strong reducing properties. They are prepared by reduction of chromium(III) compounds with zinc [187] or a zinc-copper couple and form dark blue solutions extremely sensitive to air. Most frequently used salts are chromous chloride [7SS], chromous sulfate [189], and less often chromous acetate. Reductions of organic compounds are carried out in homogeneous solutions in aqueous methanol [190], acetone [191], acetic acid [192], dimethylformamide [193] or tetrahydrofuran [194] (Procedure 37, p. 214). 

Although primary and secondary nitro compounds may be converted, respectively, to aldehydes and ketones by consecutive treatment with alkalis and sulfuric acid (Nef s reaction) the same products can be obtained by reduction with titanium trichloride (yields 45-90%) [565] or chromous chloride (yields 32-77%) [190]. The reaction seems to proceed through a nitroso rather than an aci-nitro intermediate [565] (Scheme 54, route b). 

Iron in acetic acid at 100° reduced 4-nitropyridine oxide quantitatively to 4-aminopyridine [170], and 3-bromo-4-nitropyridine oxide to 3-bromo-4-aminopyridine in 80% yield [170]. Chromous chloride, on the other hand, failed in the deoxygenation of nitropyridine oxides and nitroquinoline oxides [191]. 

In enediones in which two carbonyl groups of a diketone are linked by an ethylenic bond tin [174] and chromous chloride [196] reduce only the double bond, and none of the conjugated carbonyl groups. A double bond conjugated with one carbonyl group only is not reduced. Refluxing cholest-4-ene-3,6-dione with chromous chloride in tetrahydrofuran yielded 49% of 5/S-cholestane-3,6-dione, and a similar reduction of cholesta-l,4-diene-3,6-one gave 5)S-cholest-l-ene-3,6-dione [196]. 

Lithium aluminum hydride reduced p-benzoquinone to hydroquinone (yield 70%) [576] and anthraquinone to anthrahydroquinone in 95% yield [576]. Tin reduced p-benzoquinone to hydroquinone in 88% yield [174] Procedure 35, p. 214). Stannous chloride converted tetrahydroxy-p-benzoquinone to hexa-hydroxybenzene in 70-77% yield [929], and 1,4-naphthoquinone to 1,4-di-hydroxynaphthalene in 96% yield [180]. Other reagents suitable for reduction of quinones are titanium trichloride [930], chromous chloride [187], hydrogen sulfide [248], sulfur dioxide [250] and others. Yields are usually good to excellent. Some of the reagents reduce the quinones selectively in the presence of other reducible functions. Thus hydrogen sulfide converted 2,7-dinitro-phenanthrene quinone to 9,10-dihydroxy-2,7-dinitrophenanthrene in 90% yield [248]. 

REDUCTION WITH CHROMOUS CHLORIDE Preparation of Chromous Chloride [75 ]... 

A solution of 1 g of 2-iodo-A -3-ketosteroid in 50-100 ml of acetone is treated under carbon dioxide portionwise with 20 ml of the solution of chromous chloride. After 10-30 minutes water is added and the product is filtered or extracted with ether and recrystallized. Yield of pure A -3-ketosteroid is 60-63%. 

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