Chromyl chloride, preparation

Bromobenzaldehyde has been prepared by the oxidation of -bromotoluene with chromyl chloride/ by saponification of the acetal from />-bromophenylmagnesium bromide and orthoformic ester/ by the oxidation of ethyl -bromobenzyl ether with nitric acid/ by the oxidation of /j-bromobenzyl bromide with lead nitrate/ and by the hydrolysis of i-bromobenzal bromide in the presence of calcium carbonate. ... 

Nitrobenzaldehyde has been prepared from />-nitrotoluene by treatment with isoamyl nitrite in the presence of sodium methylate,1 by oxidation with chromyl chloride,2 cerium dioxide,3 or chromium trioxide in the presence of acetic anhydride.4 It can also be prepared by the oxidation of -nitrobenzyl chloride,5 7>-nitrobenzyl alcohol,6 or the esters of -nitrocinnamic acid.7... 

Alkenes have also been converted to more highly oxidized products. Examples are (1) Treatment with KMn04 in aqueous acetone containing acetic acid gives a-hydroxy ketones. (2) 1,2-Disubstituted and trisubstituted alkenes give a-chloro ketones when oxidized with chromyl chloride in acetone RCH=CR R"—> RCOCCIR R". (3) a-Iodo ketones can be prepared by treating alkenes with... 

Hydratropaldehyde has been prepared by hydrolysis of phenylmethylglycidic ester,2 3 4 by chromyl chloride oxidation of cumene,5 by the elimination of halogen acid or water from halohydrins or glycols,5 8 and by the distillation at ordinary pressure of methylphenylethylene oxide.9,10... 

Etard reagents (chromyl chloride and some derivatives) suffer from the problem that occasionally they can exhibit a lack of selectivity and low yields. They are useful in the selective oxidation of aromatic side-chains to a carbonyl group, aldehyde or ketone but in many instances, the formation of the initial complex is slow and yields are low because of difficulties in the work-up which lead to undesired over-reaction. Attempts have been made to solve the problems by the use of sonication [134]. A simple preparation of the liquid reagent was proposed and the Etard reaction itself together with the hydrolytic step were conducted under sonication, with some success (Scheme 3.25). 

Chromyl chloride is used in many organic synthetic reactions including oxidation and chlorination. It also is used as a catalyst in olefin polymerization in the preparation of chromium complexes and as a solvent for chromic anhydride. 

Chromyl chloride is prepared by reacting chromium(III) chloride with hydrochloric acid ... 

Compounds where urea takes the place of ammonia are known which correspond to the hexaquo-chromic salts these contain six molecules of urea bound to the central chromium atom through oxygen, and are prepared by the action of chromyl chloride on urea. The... 

Preparation and Properties of Chromyl Chloride, a. Put a mixture of 1 g of sodium chloride with 1 g of potassium dichromate into a dry test tube, add a few drops of concentrated sulphuric acid, and close the tube with a stopper provided with a gas-discharge tube. Lower the other end of the latter into another dry test tube submerged in a beaker with cold water. Slightly heat the reaction mixture. What collects in the receiver Write the equations of the reactions. 

Preparation of Chromium(VI) Oxysulphate. (Perform the experiment in a fume cupboard ) a. Preparation of Chromyl Chloride. Assemble an apparatus as shown in Fig. 127a. Dry 12.5 g of sodium chloride and 20 g of potassium dichromate in a drying cabinet at 100-120 °C. Rapidly mix them in a mortar and put the mixture into flask 1. Add 22 ml of a 98% sulphuric acid solution to the reaction... 

Chromyl chloride Cr02Cl2 can be prepared by distillation from a mixture of an alkali metal chloride and concentrated sulfuric acid with an alkali metal dichromate or Cr03. It can also be prepared from dichromate and HC1, Cr03 and an acid chloride such as PC15 or HS03C1,222 or Cr03 and A1C13 in molten LiCl/NaCl/KCl.1371... 

The method described is a modification of that of Gatter-mann and Koch.1 The aldehyde has also been prepared by related methods such as the action of hydrogen cyanide and hydrogen chloride on toluene in the presence of aluminum chloride,2 and nickel carbonyl with toluene and aluminum chloride.3 The reduction of />tolunitiile by stannous chloride forms the aldimine which on hydrolysis gives an almost quantitative yield of the aldehyde.4 />-Xylene can be oxidized by various reagents, particularly chromyl chloride,5 to />-tolualdehyde. 

PCC is usually prepared using the description of Corey and Suggs,189 although other procedures have been reported.190,191 Agarwal et al. published that preparing PCC by addition of CrC>3 over a pyridinium hydrochloride solution avoids the handling of poisonous chromyl chloride.192... 

In a similar fashion, chromyl chloride, normally a very vigorous oxidant, can be used to selectively prepare aldehydes and ketones once it has been adsorbed onto silica-alumina. Unfortunately, double bonds are still cleaved under the reaction conditions. 

Chromyl Chloride, CrOjClj, sometimes termed cldorocliromic acid, is readily prepared by distilling a mixture of fused potassium chromate or dichromate and sodium chloride with concentrated sulphuric acid ... 

Sodium Chlorochromate, NaClCrOj. HaO, may be prepared from sodium chromate and chromyl chloride as reddish-yellow crystals, somewhat unstable, especially in solution. A chromoiodate, Na2Cr03. lOg.HgO, has also been described. ... 

Chromyl chloride, Cr202Cl2, a dark-red liquid (mp -96.5 °C, bp 117 °C, d 1.911), is prepared from chromium trioxide or sodium dichromate, hydrochloric acid, and sulfuric acid [665]. The reagent is used in solutions in carbon disulfide, dichloromethane, acetone, tert-butyl alcohol, and pyridine. Oxidations with chromyl chloride are often complicated by side reactions and do not always give satisfactory yields. The mechanism of the oxidation with chromyl chloride, the Etard reaction, is probably of free-radical nature [666]. Complexes of chromyl chloride with the compounds to be oxidized have been isolated [666, 667, 668]. 

Other oxidants of hexavalent chromium are chromyl chloride and di-/er/-butyl chromate. Chromyl chloride adsorbed on alumina-silica gel from its solution in dichloromethane oxidizes aliphatic and aromatic alcohols at room temperature within hours in 77-100% yields [675]. Di-tert-butyl chromate, prepared in situ from chromyl chloride in tert-butyl alcohol at -70 °C, gives comparable results under similar conditions [674. Di-tert-butyl chromate, prepared from chromium trioxide and tert-butyl alcohol, oxidizes primary aliphatic and aromatic alcohols to the corresponding aldehydes even at low temperatures (1-2 °C) [677, 678]. 

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