THE CRYSTAL STRUCTURES OF SEVERAL cis-1,2-DIHALOBENZOCYCLOBUTENES (thesis)
The crystal structures of the cis-l, 2-diiodo-s dibromo-, and dichloro- derivatives of benzocyclobutene have been determined by single-crystal x-ray- diffraction methods. The halogen-substituted double ring system shows a combination of resonance and steric strain effects on the bond distances and molecular configurations. C/sub 8/H/sub 6/Br/sub 2/ and C/sub 8/H/sub 6/I/sub 2/ are isomorphous cr ystallizing in space group Pua2/sub 1/ with four molecules per unit cell. The structure of the dibromo- derivative has been determined by three- dimensional least-squares refinement with 613 independent reflections. The full- matrix least-squares refinement technique is compared to the diagonal approximation method. The four- and sixmembered rings are nearly coplanar, sharing a bond shortened by ring strain. The other bond lengths are in agreement with values predicted for nonstrained systems. A similar arrangement was found to be consistent with the data for CB/sub 8/H/sub 6/I/sub 2/. The crystal structure of C/sub 8/H/sub 6/Cl/sub 2/ has been determined at room temperature and at liquid nitrogen temperature by- single-crystal x-raydiffraction methods, including three-dimensional leastsquares refinements. At both temperatures the crystals have essentially the same monoclinic structure in space group P2/sub 1/c with four molecules in the unit cell. The bond distances derived from the room- temperature determination differ from those found at low temperature in a manner attributable to anisotropic thermal motions. The low-temperature determination shows the side bonds of the four-membered ring shortened to l.448 plus or minus 0.0l0A, presumably because of cooperative resonance effects of the chlorine atoms and the phenyl ring. The two carbon atoms attached to the chlorine atoms are 1.562 plus or minus 0.0l4A aparts with the steric strain effects predominating over resonance shortening. (auth)
- Research Organization:
- California Univ., Berkeley, CA (US). Lawrence Radiation Lab.
- DOE Contract Number:
- W-7405-ENG-48
- NSA Number:
- NSA-13-017836
- OSTI ID:
- 4233501
- Report Number(s):
- UCRL-8803
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-59
- Country of Publication:
- United States
- Language:
- English
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