Etard

In the conversion of strychnine to strychninic acid, Tafel pointed out that a second acid is formed, identical with Gal and Etard s dihydrostrychnine and now known as wostrychninic acid. The preparation of... 

Benzaldehyde.—The aldehydes of the aromatic seiies may also be obtained by the oxidation of a methyl side-chain with chromium oxychloride. The solid brown product, C,H,.CH.)(CrO,CL)2, formed by adding C1O2CIJ to toluene, dissolved in carbon bisulphide, is decomposed with water, and benzaldehyde sepaiates out (Etard). Other methods for pie-paring aromatic aldehydes are (i) the Fiiedel-Crafts reaction, in which a mixture of carbon monoxide and hydrogen chloride aie passed into the hydrocaibon in presence of aluminium chloride and a little cuprous chloride,... 

The mechanism of the Etard reaction is not completely known. 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 not fully settled, though many proposals have been made as to its structure and as to how it is... 

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 . ... 

Oxidation of Arylmethanes - Electrochemical Alternative Routes to the Etard Reaction... 

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 ... 

Etard, M. A., The life and work of Eugene Demargay, Chem. News, 89,... 

According to K. von Hauer,36 a soln. of potassium bromide sat. at 15° deposits almost all its bromide when repeatedly heated and cooled with an excess of potassium iodide and potassium iodide dissolves in a sat. soln. of potassium chloride almost as copiously as in water. A. Etard has measured the mutual solubility of potassium bromide and chloride, potassium chloride and iodide, and potassium bromide and iodide, and found that the sum of the salts dissolved can usually be represented as a straight line when plotted with temp., and the vanishing point where the water has disappeared, coincides with the m.p. of the constituent with the lower m.p. The solubility of the ternary system potassium chloride, bromide, and iodide, could not be determined as a function of temp, because the three salts cannot exist simultaneously in a sat. soln.—the chloride remains undissolved in the presence of the other two salts. G. J. Mulder (1864) found that the solubility of potassium iodide is diminished in the presence of potassium sulphate. J. N. Bronsted measured the solubility of potassium iodide in soln. of potassium hydroxide of different cone. 

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