XLIX.—Crystallographical relations of the derivatives of dibenzoylcinnamene

Alfred E. Tutton
1890 Journal of the Chemical Society Transactions  
IN this paper are presented the results of the crystallographical examination of several of the new compounds described by Drs. Japp and Klingemann i n the preceding communication. Eleven wel!crystallising substances derived from dibenzoylcinnamene have beeit examined, and several interesting relations between their symmetry discovered which may be of use in further elucidating the question uf the general relation between crystalline form and chemical cornposit ion. The substances investigated
more » ... ances investigated were :-Dibenzoylcinnamene itself ; Triph enylcrotolactone, isomeric with dibenzoylcinna,mene ; Dibenzoylciniismenimide ; Triphenylpyrrholone, the imide of triph enFlcrotolactone ; Methyl-, ethyl-, propyl-, and allyl-derivatives of triphenylpyrrho- Bromine-derivatives of methyl and ethyl triphenylpyrrholone ; A compound of the composition C"H"O. lone ; The main interest of the work lies in the isomorphous and morphutropic relations observed between the alkyl-derivatives of triphenylpyrrhoione. The addition of a CH, group is found, in the particular cabes examined, to be accompanied by a very slight alteration in the axial ratios without any disturbance of the crystallographic symmetry, similar to 5hat which occurs when metals of the same chemical family are substituted for one another in their salts. The problem has been somewhat complicated by the prevalence of polymorphism, several of the alkyl-derivatives being found in two and probably even three distinct hams. A remarkable case of dispersion of optic axes for different colours of the spectrum has been found in case of the monoclinic variety of ethyl triphenylpyrrholone. Between the red and the green the dispersion amounts to more than 54", and is accompanied by a crossing of the optic axial planes. Consequently the interference figure in white light is exceptionally complicated, somewhat resembling the well-known one of brookite in the rhombic system. The paper is concluded by the results of an investigation as to the identity or otherwise of the oxylepidenic and isoxylepidenic acids 7 15 described by Zinin. I n the preceding paper the two substances have been shown to be probably identical from chemical considerations ; their crystalline forms are now shown to be identical. The goniometrical measurcments have been made wit,h the large horizontal circle goniometer supplied by Fuess, of Berlin, which reads accurately t o half a minute of arc. The optic axial measurements were made with the universal apparatus described by Professor Groth and constructed by Fuess, and the determinations of extinctions were made by means of a polarising microscope constructed f o r the author by Swift. Melting point 129". Crystallised from a mixture of chloroform and carbon bisnlphide. This compound was obtained five years ago by Japp and Miller (Trans., 1885, 35), and forms the stock material from which the ten following substances are derived. An improved method of preparation from benzil, acetophenone, and alcoholic potash is given in Part I1 of the preceding paper. The specimen dxamined consisted of very small, slightly yellow prisms; the largest observed were about 2 mm. long and 2 mm. thick. They were generally very much striated and distorted, and the reflections were consequently not good. They were much aggregated, several parallel crystals frequently growing together. System : rhombic. Ratio of axes: a : b : c = 0.6898 : 1 : 0.6500. Forms observed : a = (100)mPcn ; b = (010)mPoo ; p = ( l l O ) m P ; p ' = (130)mP3; 'yn = ( 1 0 1 ) P~; T = {112!iP. Habit : prismatic. " I 6 010 130 t% 100 FIG. 1. FIG. 2. 7 1 7 developed besides the prism faces, is inclined 81" 32' to the vertical axiA. The crystals, moreover, are biaxial, and the optical propertics indicate the presence of only one plane of symmetry. The disposition of the other faces exhibited by many of the crystals also points to mono-symmetry. The result of a large number of measurements of the prism zone shows that the angle bet,ween a a n d p is sligtitly less, and that between p and b slightly greater than 45". Thus out of 40 measurements of up, 34 were less than 45", and of 32 measurements of pb, 31 were greater than 45". The crystals are therefore monoclinic, with a prism zone of nearly 45".
doi:10.1039/ct8905700714 fatcat:xhqpumms3jdzri25wxezuxhndu