Ethere Zeisel method

Ether Cellulose, polyvinyl ethers Zeisel method 199... 

It should be mentioned that the formation of methyl iodide by heating methyl ethers with concentrated hydriodic acid is quantitative and is the basis of the Zeisel method for the determination of methoxyl groups. 

Proof of structure of a new ether would involve cleavage by hydriodic acid and identification of the products formed. Cleavage is used quantitatively in the Zeisel method to show the number of alkoxyl groups in an alkyl aryl ether. 

The classical Zeisel method for the determination of ether (59) consists of digesting the substrate with hydrogen iodide. Analysis shows that the reaction proceeds in a favorable manner as designated by Saville. Sulfides do not interfere with the determination because the hard-soft combination is incorrect in such cases. 

Methyl groups are frequently found as esters of uronic acids and sometimes as ethers of sugar residues. Ether-linked methyl groups and total methoxyl are determined by the Zeisel method 13). Methyl esters or glycosides may be differentiated from methyl ethers by the action of alkali and acid, respectively, which will saponify the ester or glycoside but have no effect on the ether. The ester or glycosidic methoxyl can be distilled as methanol and be determined colorimetrically after oxidation to formaldehyde and condensation with Schiff reagent 14). 

The Zeisel method has been used to determine ether groups in cellulose and polyvinyl ethers [58]. 

The Zeisel method is based upon the fact that alkoxyl groups, whether in ethers or esters, are decomposed by heating with strong hydriodic acid to jneld alkyl iodides. The latter are absorbed in alcoholic AgNO.s and estimated as Agl. ... 

Naphthyl methyl ether.—Dissolve 3-6grams(3-naphthnl in I3 5 c.c. 10 per cent, caustic soda solution, add 3 c.c. meth l sulphate, warm the liquid gently and shake vigorously. In. i short time the naphthyl methyl ether separates as a solid mass. The product is heated for ten minutes on the water-bath, a little water is added, and the naphthyl ether filtered and washed with water. It is crystallised from alcohol and deposits in lustrous plates m. p. 70—72°. The yield is theoretical. It may be used for analysis by Zeisel s method. 

Zeisel s method is used to determinate methoxy and ethoxy groups. It is a method of both qualitative and quantitative organic analysis. It is mentioned under the heading General Methods of Analysis of the 10th edition of the french pharmacopeia. It ends with an argentometric titration. Its principle is based on the reaction of hydroiodic acid (Berthelot s universal reductor) with ether oxides, according to the reactions... 

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