empirical least-squares treatment of Figure 4 to be 97, 97, and 94°, respectively, while the observed values are 94, 92, and 92°. The Pd-bridge Cl bonds opposite the olefinic groups are 0.1 A longer than the Pd-Cl bond lengths in (PdCl2)". However, the ring angles in all three palladium compounds are the same. This observation can be rationalized by invoking the "trans" effect and requiring the palladium orbitals to be highly directional in character. This can be contrasted to the Ni2Cl84_ anion with a "well-behaved" Ni-Cl-Ni angle of 99.1 °. GaCl3 has a Ga-Cl-Ga angle approximately 5°less than that predicted by the Ga-Cl distance of 2.29 Á. Dahl33 has pointed out that one of the factors leading to anomalously acute bridge angles is metalmetal bonding, and perhaps this is the case in GaCl3.
If the frequent articles in Chemical and Engineering News (1) are any indication, computational chemistry has come of age as a tool in the laboratory. As computational software moves into the chemistry mainstream, there is a growing need to bring molecular modeling into undergraduate courses. Brown, for instance, has made a convincing case for introducing undergraduates to computational chemistry (2). He concludes that "as computers grow faster and less expensive, and are found increasingly in chemists' laboratories, computational investigations of chemical systems will be performed by chemists trained in subdisciplines other than computational and theoretical chemistry. In light of these observations, it is imperative that the undergraduate chemistry curriculum introduce students to computational chemistry."As a part of cooperative efforts to modernize the physical chemistry laboratory experiments at our three schools, we now include molecular modeling projects in both semesters of our courses. These projects introduce students to semiempirical and ab initio molecular orbital calculations and how they can be used in conjunction with experimental observations. We are using 266-MHz Pentium II PCs with 64 or 128 MB of RAM running Windows 95 with Quantum CAChe (3) and Gaussian 94W (4 ) as tools in these projects.Along with the use of modern computational methods, we have given our projects a research flavor by basing them on problems that are most easily solved through collaboration. Online collaboration is a convenient way to facilitate communication among students as the projects develop-especially if more than one college is involved. Following the example of Long and Zielinski (5) almost all of the communication during these two projects was online, either by email or through the World Wide Web.
after stirring 5 min the mixture was washed with 1 N HC1 and NaHCOa solution, dried, and evaporated.The residue was dissolved in benzene, filtered to remove some dicyclohexylurea, and chromatographed on 150 g of silica gel. Elution with 20-100% ethyl acetate in Skellysolve B gave major peaks corresponding to epimeric glycols of structure 4 (R = CH2CC13). The less polar, 700 mg, showed one spot on tic-silica gel, 50% ethyl acetate-cyclohexane; the more polar, 800 mg, showed two very close spots on the same tic system. The R¡ values of these trichloroethyl esters were similar but slightly greater than those of the corresponding methyl esters, above.To 667 mg of the less polar glycol 4 (R = CH2CC13) above was added 16.5 ml of pyridine and then, at 0°, 1.67 ml of methanesulfonyl chloride. The mixture was stirred at 0°for 10 min, and 1.75 hr longer with the ice bath removed. It was then again cooled to 0°, 15 ml of water was added, and the mixture was extracted with ethyl acetate. This was washed several times with cold dilute hydrochloric acid and aqueous sodium bicarbonate, dried, and evaporated. The crude bismesylate was stirred in 53 ml of acetone and 26 ml of water under nitrogen at 25°o vernight. The solution was concentrated in vacuo and extracted with ethyl acetate, which was washed, dried, and evaporated. The residue was chromatographed on 75 g of silica gel and eluted with increasing amounts of ethyl acetate in Skellysolve B. After two main peaks of material, 276 and 103 mg, of unrearranged glycol monomesylates was eluted 34 mg of ¿/-8-isoprostaglandin Ei trichloroethyl ester showing two olefinic protons between 5.0 and 6.0 ( 33 at 5.28,7=15 and 9.5 cps, and Hu at 5.7, 7=15 and 7 cps), two protons of the trichloroethyl group as a singlet, 4.8, and two carbinolic protons as multiplets between 3.9 and 4.5. This was followed by 12 mg (5) L. H. Piette and W. A. Anderson, J. Chem. Phys., 30, 899 (1959), eq 23.
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