Chromyl chloride, oxidation with

Chromyl chloride oxidation of alkenes proceeds via the formation of adducts at a rate necessitating stopped-flow techniques. At 15 °C the formation of 1 1 adduct from styrene and oxidant in CCI4 solution is simple second-order with 2 = 37.0 l.mole .sec . Measurements with substituted styrenes yielded = — 1.99. E = 9.0 kcal.mole and = —23.8eu for styrene itself. Hydrolysis of the styrene adduct yields mostly phenylacetaldehyde (76.5 %)and benzaldehyde (21.1 %). Essentially similar results were obtained with a set of 15 alkenes and... 

Similar oxidative rearrangements to produce carbonyl compounds have been carried out with thallium(III) nitrate557 or peroxytrifluoroacetic acid-BF3.558 The Jones reagent (Cr03—H2S04) in the presence of a catalytic amount of Hg(II) is also effective.559 Chromyl chloride oxidation, when combined with reductive workup, is a simple, convenient one-step method to convert 2,2-disubstituted 1-alkenes to aldehydes.560,561... 

Oxidation of the trihydroxypropyl compound 7 or the aldehydes 38 and 40 with chromium trioxide in acetic acid or 50% sulfuric acid furnishes the 3-carboxylic acids, which readily decarboxylate to the 3-unsubstituted compounds at their melting points. " In contrast, the 3-methyl-l-phenyl compoimd is not appreciably attacked by chromiiun trioxide, potassium permanganate, or selenium dioxide. Chromyl chloride oxidation of 7 does not give the aldehyde 38 but apparently provides the tetraflavazolyl ether 41. The inertness of the 3-methyl group is emphasized by its stability toward bromine and its lack of reaction with benzaldehyde." ... 

Precaution Flamm. solid oxidizes in dry air dec. in moist air dec. by acids vioient reactions with lead dioxide, potassium chlorate, potassium nitrate incompat. with oxidizers, chromyl chloride contact with acids liberates toxic gas... 

The kinetics of the chromyl chloride oxidation of the carbon-carbon double bond of styrene have been examined using stopped-flow spectrophotometry/ the product being a chromyl chloride-styrene adduct. The rate is first order with respect to each reactant and a linear free-energy relationship (Hammett correlation) has been shown to hold for a variety of substituted groups. The data are consistent with a mechanism involving electrophilic attack by the chromium(vi) species on the double bond to yield the adduct, which decomposes on hydrolysis to give phenylacetalde-hyde and benzaldehyde as the major reaction products ... 

Oxidation (low yield) of aryl or cycloalkyl methyl groups to aldehydes with chromyl chloride... 

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... 

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

When chromyl chloride (Cr02Cl2) is mixed with urea the mixture combusts immediately after being formed. The interpretation is rather problematic. It may be due to oxidation. 

ALDEHYDES BY OXIDATION OF TERMINAL OLEFINS WITH CHROMYL CHLORIDE 2,4,4-TRIMETHYL-PENTANAL, 51, 4 ALDEHYDES FROM ACID CHLORIDES BY MODIFIED ROSENMUND REDUCTION 3,4,5—TRIMETHOXYBENZ-ALDEHYDE, 51, 8 ALDEHYDES FROM ACID CHLORIDES BY REDUCTION OF ESTER MESYLATES WITH SODIUM BOROHY-DRIDE CYCLOBUTANECARBOXAL-DEHYDE, 51, 11... 

Oxidation, of primary alcohols to aldehydes, 52, 5 of terminal olefins with chromyl chloride, 51, 6 of 2,4,4-trimethyl-1-pentene with chromyl chloride, 51, 4 with chromium trioxide-pyridine complex, 52, 5... 

Dimethy1-2-neopentylpen-tanal, by oxidation of 4,4-dimethy1-2-neopentyl-1-pen-tene with chromyl chloride, 51, 6... 

In this state, chromium compounds are usually coloured yellow or red (but due to charge transfer (p. 60) and not to the presence of d electrons on the chromium ion). The only halide known is the unstable chromium(VI) fluoride CrF6, a yellow solid. However, oxide halides are known, for example Cr02Cl2 ( chromyl chloride ), formed as a red vapour when concentrated sulphuric acid is added to a chromate(VI) (or dichromate) mixed with a 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). 

ALDEHYDES BY OXIDATION OF TERMINAL OLEFINS WITH CHROMYL CHLORIDE 2,4,4-TRIMETHYLPENTANAL... 

Aldehydes by Oxidation of Terminal Olefins with Chromyl Chloride... 

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