Some symmetrical Ar3C and unsymmetrical (C6C15)3-xAr,C radicals with different chlorine substitution patterns (x = 1, 2; Ar: 2H-C6HC14, 3H,5H-C6H2C14, 4H-C6HC14, C6H5) are prepared. X-ray crystal structures for most of them have been obtained at room temperature. The general conformations are conditioned by the great volume of the chlorine atoms in the ortho positions resulting in unsymmetrical, propellerlike conformations. Experimental evidence of the steric shielding of the trivalent carbon atom, as well as the practical nonexistence of the so-called buttressing effect, is given. The steric shielding is in correlation with the observed stabilities. The magnetic susceptibilities of the radicals are discussed and related to molecular packing and spin densities in terms of McConnell's theory, when antiferromagnetism is observed. The g-factors, hyperfine coupling constants (hcc) of IH and I3C nuclei, and line widths of the radicals are determined at several temperatures by ESR experiments in solid-state and isotropic solutions. Different conformational dynamic behaviors are traced to the number of chlorine atoms in ortho positions. Temperature-dependent line widths are explained by the relative contribution of the modulation of the dipolar hyperfine interaction through molecular tumbling and chlorine nuclear quadrupolar relaxation mechanism. The hcc values have been calculated according to the INDO method with the experimental X-ray geometries and compared with the experimental values; a g o d agreement is obtained. The assignment of the I3C satellites to bridgehead and ortho positions is confirmed IntroductionIn the course of our studies on derivatives of perchlorotri-

maléate (10%, 8% yield). The last two fractions were essentially pure exo ester, bp 123°(22 mm), m24d 1.4675 (lit.37 bp 109-110°( 18 mm)).

In our study, we did not find significant differences between the use of one or two drains after lobectomy or bilobectomy in relation to early postoperative outcome. However, the use of only one drain is more economical and is less painful for patients, without any additional adverse consequences.

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