Chromous chloride reduction

Requirements and tests for Pyroxylin type NC are described in Specs listed here as Refs 51 52 and for Technical NC(for use in organic coatings) in Ref 53. Several US std tests are described in Ref 55. In Ref 49 is described detn of N content of NC by IR spectrophotometry and in Ref 55 detn of NC by chromous chloride reduction. One of the latest methods on detn of N content in NC by ferrous-titanous titration is described in Ref 44. This test will be included in the next edition of US Military Standard Spec... 

Refs l)K.Van Keuren, "A Procedure for Chemical Analysis of Composition A-3 , NAVORD Report 1781, US Naval Ordnance Laboratory, White Oak, Md. (1951) la)S.M. Kaye, PATR 1936 (1953) (Nonaqueous titration method for detn of RDX content in Comp A-3) 2)Anon, Military Explosives , TM 9-1910 (1955), 271 (Identification of Composition A-3) 3)Purchase Description X-PA-PD-940 (1956) (Karl Fischer moisture detn) 4)Federal Test Method Std No 141 (1958), Method 4082 (Karl Fischer moisture detn) 4a)C.C.Jamison, "Determination of Nitrogenous Coumpounds of Ordnance Interest by Chromous Chloride Reduction , PicArsn, FRL TechMemo ACS-3-60 (I960) 5)U.S. 

Nitrogenous Compounds of Ordnance Interest by Chromous Chloride Reduction, PATM ACS-3-60 (I960) 26b) R.G. Gutmacher et al, "Some Recent... 

Refs 1) F. Feigl, "Spot Tests in Organic Analysis, Elsevier, NY (I960), pp 167-69 178-79 2) C.C. Jamison, Jr, "Determination of Nitrogenous Compounds of Ordnapce Interest by Chromous Chloride Reduction , PATM ACS-3-60 (I960) 3) R.G. Gutmacher et al, "Some Recently... 

Erythrinadienols have also been transformed to dibenzazonines. Thus, when 93 was heated with HC1 in MeOH, a 50% yield of the pentasubstituted dibenzazonine 94 was obtained (Scheme 24). This compound could also be prepared directly from 92 by chromous chloride reduction (70). Erysodienol (95)... 

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... 

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 ... 

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],... 

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). 

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 ]... 

Chromous chloride is a powerful reductant sometimes used to prereduce analyte to a lower oxidation state. Excess Cr2+ is oxidized by atmospheric 02. Sulfur dioxide and hydrogen sulfide are mild reducing agents that can be expelled by boiling an acidic solution after the reduction is complete. 

HMX may be detd by the Chromous Chloride Method of Gutmacher Selig (Ref 26b). The method, essentially, consists of the reduction of HMX with CrCl3 in a dimethylformamide ... 

V2 ml of Fe alum soln used to titrate excess chromous chloride N Normality of Fe alum soln 1.234 = the factor obtd by dividing the mw of of HMX (296) by the total election change of 4 nitro groups undergoing reduction (6x4= 24)... 

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