Chromyl chloride, reaction

Several laboratory explns have occurred when using the reaction between P trichloride and acetic acid to form acetyl chloride. Poor heat control probably caused formation of phosphine (Ref 2). Two later explns may have been due to ingress of air and combustion of traces of phosphine (Ref 8). Al powder burns in P trichloride vapor (Ref 4) K ignites and molten Na explds on contact (Ref 3). Each drop of chromyl chloride added to well-cooled P trichloride produces a hissing noise, incandescence, and sometimes an expln (Ref 5). It reacts with fluorine with incandescence (Ref 1), and with ignition... 

The name Etard reaction is often applied to any oxidation with chromyl chloride, for example, oxidation of glycols (19-7) and Alkenes (19-10). 

The effect of solvent upon k2 has been reported , and it was concluded that the activated complex is not sufficiently polar to be called ionic . The oxidations of toluene and triphenylmethane exhibit primary kinetic deuterium isotope effects of 2.4 and ca. 4 respectively. No isotopic mixing occurred during formation of the Etard complex from a mixture of normal and deuterated o-nitrotoluene . The chromyl chloride oxidation of a series of substituted diphenylmethanes revealed that electron-withdrawing substituents slow reaction while electronreleasing groups have the opposite effect, the values ofp andp being —2.28 + 0.08 and —2.20 + 0.07 respectively . ... 

Therefore chromyl chloride, already mentioned on p.200 for its oxidation reactions, hydroiyses very violently forming hydrogen chloride. 

Anilines are converted into nitrosoarenes ArNO by the action of hydrogen peroxide in the presence of [Mo(0)(02)2(H20) (HMPA)]224, whereas catalysis of the reaction by titanium silicate and zeolites results in the formation of azoxybenzenes ArN (0)=NAr225. Azo compounds ArN=NAr are formed in 42-99% yields by the phase-transfer assisted potassium permanganate oxidation of primary aromatic amines in aqueous benzene containing a little tetrabutylammonium bromide226. The reaction of arylamines with chromyl chloride gives solid adducts which, on hydrolysis, yield mixtures of azo compounds, p-benzoquinone and p-benzoquinone anils 234227. 

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). 

Etard reaction org chem Direct oxidation of an aromatic or heterocyclic bound methyl group to an aldehyde by utilizing chromyl chloride or certain metallic oxides. a tar re,ak-sh3n ... 

In a 5-1. three-necked flask fitted with a mechanical stirrer, a thermometer, and a dropping funnel equipped with a calcium chloride drying tube are placed 112.2 g. (1.00 mole) of freshly distilled 2,4,4-trimethyl-1-pentene (Note 1) and 11. of methylene chloride (Note 2). The flask is immersed in an ice-salt bath, and the stirred solution is cooled to 0-5°. A solution of 158 g. (1.02 moles) (Note 3) of freshly distilled chromyl chloride (Note 4) in 200 ml. of methylene chloride (Note 5) is added dropwise with stirring from the dropping funnel while the temperature is maintained at 0-5° (Note (i). The reaction mixture is stirred for 15 minutes, and 184 g. of 110 05% technical... 

Reaction with hydrochloric acid yields chromyl chloride ... 

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 reacts violently with alcohol, ammonia, and turpentine, igniting these liquids. Reactions with other oxidiazable substances can be violent. The liquid is corrosive and possibly a poison. Skin contact can cause bhs-ters. Exposure to its vapors causes severe irritation of the eyes, nose, and respiratory tract. Prolonged or excessive inhalation can cause death. 

Sodium azide is a toxic as well as an explosive substance (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nd e(j New York John Wdey Sons). Although inert to shock, violent decomposition can occur when heated at 275°C. Contact of solid or solution with lead and copper must be avoided. Reactions with halogens, carbon disulfide, or chromyl chloride can be explosive. Dissolution in water produces toxic vapors of hydrazoic acid. The salt is an acute poison causing headache, hypotension, hypothermia, and convulsion. 

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. 

Pour two or three drops of the product into a beaker with water. What is observed Establish what ions are present in the solution. Write the equations of the reactions. What class of chemical compounds does chromyl chloride belong to ... 

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... 

The mechanism of the Etard reaction is not completely known.291 An insoluble complex is formed on addition of the reagents, which is hydrolyzed to the aldehyde. The complex is probably a kind of acylal, but what the structure is is not fully settled, though many proposals have been made as to its structure and as to how it is hydrolyzed. It is known that ArCH2CI is not an intermediate (see 9-20), since it reacts only very slowly with chromyl chloride. Magnetic susceptibility measurements292 indicate that the complex from toluene is 27, a structure first proposed by Etard. According to this proposal the reaction stops after... 

The reverse reaction has also been studied (18). Treating the calcined Cr03/silica with dry HC1 strips off the chromium as chromyl chloride vapor leaving one OH for each former point of attachment. The silica base is otherwise unaffected. Hydroxyl measurements before and after the stripping give a direct indication of the bonding of Cr(VI), because chromate leaves two hydroxyls per chromium removed and dichromate leaves only one. 

Chromium pentaphenyl bromide,1 (C6H5)5CrBr, is obtained by the action of phenyl magnesium bromide on anhydrous chromic chloride or chromyl chloride, the reaction in the former case probably taking the following course ... 

Reaction XC1. (a) Oxidation of Aromatic Hydrocarbons to Aldehydes by the action of Chromyl Chloride in Carbon Disulphide Solution. (Etard.) (A. Ch., [5], 22, 225.)—In this reaction the hydrocarbon and chromyl-chloride are both dissolved in carbon disulphide, and the solutions carefully mixed. An explosive intermediate compound is precipitated, and this is separated and decomposed with water to give the aldehyde. The yields are very good, but the method is not often used owing to the inconvenience of working with carbon disulphide and the dangerous nature of the intermediate compounds. 

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