Chromous sulfate

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... 

A conveniently short synthesis of a1prostadi1 begins with a mixed aldol assembly of the requisite cyclopentenone 13. This product is then oxidatively cleaved with periodate-permanganate and the alcohol moiety is protected as the tetra-hydropyranyl ether (14). Aqueous chromous sulfate satisfactorily reduces the olefinic linkage and the trans stereoisomer 15 predominates after work-up. The remainder of the synthesis of involves the usual steps, through 16 to with the exception that thexyl tetrahydrolimonyllithium borohydride is used to reduce the C-15 keto moiety so as to produce preferentially the desired C-15S stereochemistry. 

Castro CE, WC Kray (1963) The cleavage of bonds by low-valent transition metal ions. The homogeneous reduction of alkyl halides by chromous sulfate. J Am Chem Soc 85 2768-2773. 

In the reduction of C-C triple bonds with chromous sulfate in water, the key intermediate consists of a dichromium complex with the alkyne (Scheme 20.29) [119]. This configuration assures the selective formation of trans double bonds. Various substrates have been reduced in excellent yields without the occurrence of isomerizations or byproduct formation (Table 20.4). 

Scheme 20.29 Reduction of alkynes to trans-alkenes by chromous sulfate.

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). 

Geminal dihalides undergo partial or total reduction. The latter can be achieved by catalytic hydrogenation over platinum oxide [512], palladium [512] or Raney nickel [63, 512], Both partial and total reduction can be accomplished with lithium aluminum hydride [513], with sodium bis(2-meth-oxyethoxy)aluminum hydride [514], with tributylstannane [503, 514], electro-lytically [515], with sodium in alcohol [516] and with chromous sulfate [193, 197]. For partial reduction only, sodium arsenite [220] or sodium sulfite [254] are used. 

Acetylenic alcohols, usually of propargylic type, are frequently intermediates in the synthesis, and selective reduction of the triple bond to a double bond is desirable. This can be accomplished by carefully controlled catalytic hydrogenation over deactivated palladium [56, 364, 365, 366, 368, 370], by reduction with lithium aluminum hydride [555, 384], zinc [384] and chromous sulfate [795], Such partial reductions were carried out frequently in alcohols in which the triple bonds were conjugated with one or more double bonds [56, 368, 384] and even aromatic rings [795]. 

Acetylenic aromatic acids having the triple bond Hanked by carboxyl and an aromatic ring were partially reduced to olefinic aromatic acids by chromous sulfate in aqueous dimethylformamide at room temperature in high yields. Phenylpropiolic acid afforded irani -cinnamic acid in 91% yield [195]. Its sodium salt in aqueous solution gave on catalytic hydrogenation over colloidal platinum at room temperature and atmospheric pressure 80% yield of cis-cinnamic acid if the reaction was stopped after absorption of 1 mol of hydrogen. Otherwise phenylpropanoic acid was obtained in 75-80% yield [992]. 

Conjugated double bonds were also reduced in methyl 3-methyl-2-buten-oate with tributylstamane on irradiation with ultraviolet light at 70° (yield of methyl isovalerate was 90%) [1071], and in diethyl maleate and diethyl fu-marate which afforded diethyl succinate in respective yields of 95% and 88% on treatment with chromous sulfate in dimethylformamide at room temperature [974,1072]. 

Divalent chromium compounds (Cr ) (chromous compounds) including chromous chloride (CrCb) and chromous sulfate (CrS04). 

The use of zinc in ethanol to dehalogenate haloallyl halides to allenes was reported earlier by Gustavson and Demjanoff [17a, b]. This method is still a useful one and has been applied when the starting dihalides are available. Recently chromous sulfate has also been shown to be an effective reagent at room temperature [17c] (Eq. 10). 

Additional Exercises Chromous acetate, Cr(C2H302)2 chromous sulfate, CrS04-7H20 chromous chloride, CrCl2-4H20 Anderson and Riffe, J. Ind. Eng. Chem., 8, 24 (1916) Reeoura, Ann. Chim. Phys., (6) 10, 6 (1887). 

Chromous sulfate (aqueous) A fresh solution 0.4 M in chrome alum and 0.05 M in sulfuric acid is contacted with lightly amalgamated Zn... 

Castro C. E. and Kray W. C., Jr. (1966) Carbenoid intermediates from polyhalomethanes and chromium(II) the homogeneous reduction of geminal halides by chromous sulfate. J. Am. Chem. Soc. 88, 4447-4455. 

Castro and Kray have reduced the isomeric butenyl chlorides, using chromous sulfate (5). Again, allylic radicals were proposed as intermediates in the reaction. However, unlike the tin hydride reductions, 1-butene was obtained almost exclusively from each of the isomeric chlorides. The process has been described as occurring within a chromium complex. The preponderant formation of 1-butene from butenyl metal complexes has also been noted by others (12, 23, 46). 

Diamyl Phthalate Chromium Trioxide Chromous Sulfate... 

Acetylenes are reduced by chromous sulfate in water or aqueous DMF to transolefins in high yield. In the example cited, the reaction is complete at room tempera-... 

Debromination Chromous sulfate. Diphenyltelluride. Disodiumphenanthrene. Thiourea. 

Reducing agents Aluminum hydride. Bis-3-methyl-2-butylborane. n-Butyllithium-Pyridine. Calcium borohydride. Chloroiridic acid. Chromous acetate. Chromous chloride. Chromous sulfate. Copper chromite. Diborane. Diborane-Boron trifluoride. Diborane-Sodium borohydride. Diethyl phosphonate. Diimide. Diisobutylaluminum hydride. Dimethyl sulfide. Hexamethylphosphorous triamide. Iridium tetrachloride. Lead. Lithium alkyla-mines. Lithium aluminum hydride. Lithium aluminum hydride-Aluminum chloride. Lithium-Ammonia. Lithium diisobutylmethylaluminum hydride. Lithium-Diphenyl. Lithium ethylenediamine. Lithium-Hexamethylphosphoric triamide. Lithium hydride. Lithium triethoxyaluminum hydride. Lithium tri-/-butoxyaluminum hydride. Nickel-aluminum alloy. Pyridine-n-Butyllithium. Sodium amalgam. Sodium-Ammonia. Sodium borohydride. Sodium borohydride-BFs, see DDQ. Sodium dihydrobis-(2-methoxyethoxy) aluminate. Sodium hydrosulflte. Sodium telluride. Stannous chloride. Tin-HBr. Tri-n-butyltin hydride. Trimethyl phosphite, see Dinitrogen tetroxide. 

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