Dioxane, purification by distillation

Purification. Benson, McBee, and Rand, in submitting an Organic Syntheses procedure for the preparation of N-iodosuccmimide, purify dioxane only by use of sodium chips and distillation (reference to Fieser"). Checkers B. C. McKusick and T. J. Kealy used a newly opened bottle of spectroquality Reagent (MCB). In purifying the solvent for a kinetic study Burstein and Ringold state that they applied the method of Fieser and then stored the solvent over a Linde molecular sieve for at least a week. Aetually Fieser cited two methods from the literature, the first of which is designed to eliminate water and glycol acetal by hydrolysis to acetaldehyde. The methods are as follows ... 

The acetal (b 82.5 ) is removed during fractional distillation. Traces of benzene, if present, can be removed as the benzene/MeOH azeotrope by distillation in the presence of MeOH. Distillation from LiAlH4 removes aldehydes, peroxides and water. Dioxane can be dried using Linde type 4X molecular sieves. Other purification procedures include distillation from excess C2H5MgBr, refluxing with Pb02 to remove peroxides, fractional crystallisation by partial freezing and the addition of KI to dioxane acidified with aqueous HCl. Dioxane should be stored out of contact with air, preferably under N2. 

In addition to water, this solvent is almost invariably contaminated with peroxide and acetaldehyde. For removal of the peroxide impurity, dioxan is treated with tin(II) chloride and then distilled. Subsequently, the above process is repeated with anhydrous potassium hydroxide for removal of the acetaldehyde. Finally, a molecular sieve with a pore size of 0.4 nm may be used to bind traces of water. This procedure is followed again by distillation. In this way the purification of dioxane may be carried out in three steps, with triple distillation. For simplification, refluxing with lithium aluminium hydride may be attempted, followed by distillation which frees the dioxane from all three impurities in one step. 

The purification of sirupy ribose has in the past usually been carried out through the p-bromophenylhydrazone,1 7 27 a costly and laborious procedure. Recent studies of the arylamine ribosides have resulted in the discovery of a cheaper and more convenient method for the purification of ribose.28 29 30 The procedure is based upon the fact that ribose, dissolved in aqueous alcohol containing an arylamine such as aniline and an alkali metal salt such as sodium sulfate and having a pH of 4, is precipitated in high yield as a crystalline arylamine riboside-salt complex. The arylamine riboside may be extracted from this complex with dioxane and decomposed by boiling in water containing a trace of acetic acid. After the arylamine has been removed by steam distillation or through formation of a Schiff base with formaldehyde or benzaldehyde, the pure, crystalline ribose may be recovered. 

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