TY - JOUR
T1 - Structures for polymorphs of triphenylchloromethane. Triphenylacetic acid illustrates the isomorphous stable modification
AU - Kahr, Bart
AU - Carter, Randall L.
N1 - Funding Information:
ACKNOWLEDGMENT We thank the Petroleum Research Foundation (24331-G6) for support of this work. In addition, BK thanks Kurt Mislow and J.M. McBride for support of preliminary work and JMM for the use of his calorimeter. Supplementary Material Available: Observed and calculated structure factors, and hydrogen atom positions with isotropic thermal parameters (79 pages) have been deposited with the British Library Document Center as Supplementary Publication No. 90264. Copies may be obtained through the Executive Secretary, International Union of Crystallography, 5 Abbey Square, Chester CH12HU, England.
PY - 1992/8/1
Y1 - 1992/8/1
N2 - Triphenylacetic acid is isomorphous with the published structure of triphenylchloromethane (I). It crystallizes in the trigonal system, space group P3, with a=b=14.105(3)Å c=13.121(2)Å, V=2261(1)Å3, Z=6 at 175K. The structure was solved by direct methods and refined to R(Fo)=0.062. We determined the structures for two triclinic polymorphs of triphenylchloromethane, II and III. The three forms were obtained from pentane evaporated at room temperature. Phases I and III were isolated from particular solvent systems. Crystal data (II): triclinic system, space group P1, with a=13.028(l)Å, b=13.559(2)Å, c=13.969(3)Å, α=l 17.67(1)°, β=92.67(l)°, γ=91.43(l)°, V=2179.9Å3, Z=6 at 228K. The structure was solved by direct methods and refined to R(Fo)=0.045. Crystal data (III): triclinic system, space group P1, with a=14.1562(4)Å, b=21.3190(7)Å, c=13.0654(5)Å, α=99.92(3)°, β=92.68(3)°, γ=106.15(2)°, V=3712(2)Å3, Z=10 at 248K. The structure was solved by direct methods and refined to R(Fo)=0.064. A batch of crystals from pentane showed three peaks in the DSC thermogram at 99°C (III), 108°C (II), and 111°C (I). Phase III melts without being transformed to phase II or phase I. Phase II could not be isolated for calorimetric studies.
AB - Triphenylacetic acid is isomorphous with the published structure of triphenylchloromethane (I). It crystallizes in the trigonal system, space group P3, with a=b=14.105(3)Å c=13.121(2)Å, V=2261(1)Å3, Z=6 at 175K. The structure was solved by direct methods and refined to R(Fo)=0.062. We determined the structures for two triclinic polymorphs of triphenylchloromethane, II and III. The three forms were obtained from pentane evaporated at room temperature. Phases I and III were isolated from particular solvent systems. Crystal data (II): triclinic system, space group P1, with a=13.028(l)Å, b=13.559(2)Å, c=13.969(3)Å, α=l 17.67(1)°, β=92.67(l)°, γ=91.43(l)°, V=2179.9Å3, Z=6 at 228K. The structure was solved by direct methods and refined to R(Fo)=0.045. Crystal data (III): triclinic system, space group P1, with a=14.1562(4)Å, b=21.3190(7)Å, c=13.0654(5)Å, α=99.92(3)°, β=92.68(3)°, γ=106.15(2)°, V=3712(2)Å3, Z=10 at 248K. The structure was solved by direct methods and refined to R(Fo)=0.064. A batch of crystals from pentane showed three peaks in the DSC thermogram at 99°C (III), 108°C (II), and 111°C (I). Phase III melts without being transformed to phase II or phase I. Phase II could not be isolated for calorimetric studies.
KW - Differential scanning calorimetry
KW - Polymorphism
KW - Triphenylacetic Acid
KW - Triphenylchloromethane
KW - X-ray structure determination
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U2 - 10.1080/10587259208032120
DO - 10.1080/10587259208032120
M3 - Article
AN - SCOPUS:0347181805
VL - 219
SP - 79
EP - 100
JO - Molecular Crystals and Liquid Crystals
JF - Molecular Crystals and Liquid Crystals
SN - 0026-8941
IS - 1
ER -