Sodium dichromate alcohol oxidant

Alcohols are often oxidized with chromium(VI) compounds. When the alcohol is oxidized, Cr(VI) is reduced in several steps to Cr(III). The specific Cr(VI) species used depends on the scale of the process, the cost of reagents, and limitations that result firom the presence of other functional groups in the reactant. For example, the inexpensive reagent sodium dichromate (Na2Cr207) oxidizes secondary alcohols to ketones. It also oxidizes primary alcohols to aldehydes and then to carboxylic acids. Sodium dichromate in acetic acid (HOAc) is used in large-scale reactions to convert secondary alcohols to ketones. 

By the controlled oxidation of primary alcohols with a solution of potassium or sodium dichromate in dilute sulphuric acid. To avoid the further oxidation to the corresponding acid, the aldehyde is removed as rapidly as possible by distillation through a fractionating column, for example ... 

The synthesis of fluoroalkyl and chloroalkyl fluoromethyl ketones is achieved by oxidation of the corresponding alcohols by sodium dichromate and sulfunc acid in methylene chlonde in the presence of a phase transfer catalyst [49] (equation 45)... 

Write the structural formula for the product of (a) the reaction of glycerol (1,2,3-trihydroxypropane) with stearic acid, CH5(CH2)16COOH, to produce a saturated fat (b) the oxidation of 4-hydroxybenzyl alcohol by sodium dichromate in an acidic organic solvent. 

In tonnage production, acetaldehyde may be manufactured by (1) the direct oxidation of ethylene, requiring a catalytic solution of copper chloride plus small quantities of palladium chloride, (2) the oxidation of ethyl alcohol with sodium dichromate, and (3) the dry distillation of calcium acetate with calcium formate. 

Laboratory oxidation of alcohols most often is carried out with chromic acid (H2Cr04), which usually is prepared as required from chromic oxide (Cr03) or from sodium dichromate (Na2Cr207) in combination with sulfuric acid. Ethanoic (acetic) acid is a useful solvent for such reactions ... 

The oxidation of secondary alcohols with sodium dichromate in dilute sulphuric acid gives acceptable yields of ketones since these do not normally undergo extensive further oxidation under the reaction conditions (cf. Section 5.7.1, p. 587, the oxidation of primary alcohols to aldehydes). 

The oxidation of a secondary alcohol to a ketone is usually accomplished with a solution of the alcohol and aqueous acidic chromic acid in either acetone or acetic acid, with a solution of sodium dichromate in acetic acid, or by reaction of the alcohol with aqueous acidic chromic acid as a heterogeneous system. An example is the oxidation of the substituted cyclohexanol below (Reaction XXXV) with sodium dichromate in sulfuric acid (55). 

Many reagents are available to oxidize a simple secondary alcohol to a ketone. Most labs would have chromium trioxide or sodium dichromate available, and the chromic acid oxidation would be simple. Bleach (sodium hypochlorite) might be a cheaper and less polluting alternative to the chromium reagents. DMP and the Swem oxidation would also work. 

Sodium dichromate in sulfuric acid ( chromic acid, H2Cr04) is the traditional laboratory reagent for oxidizing secondary alcohols to ketones. Bleach (NaOCl) is an inexpensive, chromium-free alternative that also oxidizes secondary alcohols to ketones. Primary alcohols are usually over-oxidized to carboxylic acids under these conditions. 

Tertiary alcohols aren t oxidized by sodium dichromate. 

Sodium dichromate, Na C O Oxidizes primary alcohols to yield carboxylic acids and secondary alcohols to yield ketones (Sections 17.7 and 19.2). 

Sodium dichromate in aqueous sulfuric acid has been used since the turn of the century. It is a very strong oxidant the use of this system to oxidize primary alcohols is severely limited by overoxidation, via the aldehyde hydrate, to the corresponding acid. This problem can be p ally circumvented in the preparation of volatile aldehydes (in particular aromatic aldehydes ), by slow addition to excess alcohol and continuous removal of the aldehyde by distillation. Oxidation of secondary alcohols that are reasonably soluble is acceptable, but milder methods are now available, and are discussed in detail later. 

Similarly sodium dichromate dihydrate in DMSO is a poor oxidant, but the addition of catalytic quantities of sulfuric acid leads to the effective oxidation of a variety of alcohols to give aldehydes and ketones in good yield (80-90%).Oxidations are normally complete within 90 min at 70 C, and may be performed in commercial DMSO without the need for further purification. 

In the alcohol oxidation to carbonyl compounds several Cr(VI) reagents can be used such as CrOs in aqueous acetic acid or in other solvents along with catalytic amount of mineral acid, sodium dichromate in aqueous acetone and mineral acid or base as catalyst, sodium dichromate in acetic acid, Cr03-pyridine complex and terf-butyl chromate. 

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