Volume 2

Organic chemistry for advanced students / by Julius B. Cohen.

  • Cohen, Julius B. (Julius Berend), 1859-1935.
Date:
1907-1913
Catalogue details

Licence: Public Domain Mark

Credit: Organic chemistry for advanced students / by Julius B. Cohen. Source: Wellcome Collection.

    16/448 (page 6)
    ethane is stable at ordinary temperatures it begins to oxidise at its melting-point, and when heated with hydrogen chloride to 150° in benzene solution breaks up into tetraphenylethane, triphenylmethane, and triphenylmethyl chloride. Schmidlin1 attempted to decide between the two formulae by preparing the compound by the action of triphenylmethyl chloride on what he regarded as two isomeric magnesium derivatives of the latter compound. The two reactions should proceed as follows : 1. (C6H5)2C: H < + (C6H6)3CC1 \ 'MgCl a-compound. = (C6H5),C: H =/\ C(C6H6)3 + MgCl2 2. (C6H5)3CMgCl + (C6H6)3CC1 = 2(CUH5)3C + MgCl2 /3-compound. but no difference could be detected in the products. In discussing this question an important fact must not be lost sight of, namely, that triphenylmethyl, though colourless in the solid state, dissolves with a yellow colour. The same is the case with the tri¬ phenylmethyl halides and both conduct in liquid sulphur dioxide.2 There is consequently ionisation, which, in the case of the triphenyl¬ methyl halide, must be due to the formation of triphenylmethyl and halogen ions. It has therefore been suggested that triphenylmethyl in solution must exist at least partially in the monomolecular form. There are other facts which point in the same direction. Schmidlin 3 has shown that colourless triphenylmethyl dissolves in non-ionising solvents (benzene, chloroform) without colour, though it rapidly acquires a deep yellow tint. Piccard4 has further pointed out that, if according to Beer’s law (see footnote, p. 329) dilution does not alter the depth of colour, the yellow colour of triphenylmethyl solutions should be intensified by dilution if ionisation occurred, and he found that this was the case. On the other hand, Meyer and Wieland5 have shown that triphenylmethyl when ionised in liquid sulphur dioxide has a different absorption spectrum from that in non-disso¬ ciating solvents. Whereas the ion has a continuous spectrum, the non-conducting solutions of triphenylmethyl have a well-defined band spectrum, which they attribute to the radical as distinguished from 1 Ber., 1907, 40, 2316; 1908, 41, 425. 2 Walden, Zeitschr. pjiyS. Chan., 1903, 43, 443. 3 Ber., 1908, 41, 2471. 4 Annalen, 1911, 381, 3^7. 6 Ber., 1911, 44, 2557.