Why is ether more acidic than water

Detection of acidic groups in native cellulose by salt formation with crystal violet base


An attempt was made to uncover and determine the acidic groups in the native cellulose with the aid of a pseudobase.

Colorless crystal violet base was shaken in various media with cellulose (cotton), whereby staining of the fiber could be observed. By dissolving the dye from the fiber and determining the nitrogen content, we determined the base fixed by a certain amount of cotton.

1 g air-dry cotton fixed:

$$ \ begin {gathered} correspond to \ hfill \ Medium: mg Base: Proc. COOH \ hfill \ \ ddot Ather. . . . . . . . 2.88 0.033 \ hfill \ water. . . . . . . 3.52 0.041 \ hfill \ Petrol \ ddot ather. . . . . 3.64 0.042 \ hfill \ benzene (desiccator - \ hfill \ dry cotton) 3.45 (middle) 0.042 \ hfill \ \ end {gathered} $$

The numbers for water, petroleum ether, and benzene agree pretty well. The low ether number can be explained in such a way that ether strongly inhibits the transition from pseudoforms to ionogenic ones.

The carboxyl values ​​determined by the reaction with the crystal violet base are significantly lower than those obtained by E. Schmidt on the basis of conductometric titrations. It is now possible, however, that the carboxyl groups of the cellulose do not react quantitatively with the crystal violet base under the experimental conditions, but react with it according to their strength. Then the occurrence of the reaction would be proof of the presence of acidic groups of a certain minimum strength, while the fixed amount of base would have to be thought of as a function of the acid content and strength. Perhaps another characteristic of cotton and similar highly complex organic substances will be possible on the basis of a “crystal violet number”.

We hope to be able to further the study of these conditions through experiments on systems with known amounts of acid.

Likewise, experiments should be made on the influence of temperature and concentration.

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  1. Organic Chemistry Laboratory of the Chemical Institute of the King Alexander University in Ljubljana, Ljubljana, Yugoslavia

    M. Rebek

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Rebek, M. Detection of acidic groups in native cellulose by salt formation with crystal violet base. Colloid Journal92, 217-221 (1940). https://doi.org/10.1007/BF01510779

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