A single-crystal of ammonia, NH3, was grown in a thin-walled capillary at 178 K, and high-resolution X-ray diffraction data were obtained for this compound at 160 K in order to obtain information about electron density distribution. Conventional and multipole refinements and deformation electron density maps indicated small but significant N−H bond bending inside the NH3 tetrahedron that is in agreement with ab initio quantum-chemical calculations and the VSEPR model. Topological analysis of the experimental charge density distribution in the ammonia molecule has been performed, and the data are compared with high-level quantum-chemical calculations. Some features of the intermolecular hydrogen bonds in the crystal are discussed.

Health for financial support (GM 30757) and . K. O'Brien thanks the Graduate Alumni of Case Western Reserve University for the award of a Graduate Fellowship (August 1987-May 1988. Supplementary Material Available: Structural report for compound 6 giving methods for data collection, data reduction, structure solution and refinement, tables of crystal data, intensity measurements, structure solution and refinement, positional and thermal parameters, general temperature factor expressions, bond distances, bond angles, and intensity data, and a drawing of a single molecule showing 30% probability ellipsoids (22 pages); listing of observed and calculated structure factors (25 pages). Ordering information is given on any current masthead page.(16) This is the shortest total synthesis of (±)-trichodermol so far recorded, requiring 16 steps from 4-methylanlsole, which augurs well for the future use of 4 and related complexes. For comparison, Raphael's synthesis of trichodermin uses 19 steps from 4-methylanisole and was plagued by a difficult internal aldol reaction to generate the C ring. Still's synthesis of trichodermol elegantly overcomes this problem, but it involves 24 steps from 4-methylanisole (ref 2).

No abstract

No abstract

The X-ray crystal structure of thermally sensitive 3,3'-bicyclopropenyl (mp 198 K) has been determined at 103 K using a miniature-zone melting procedure with focused infrared light. The structural parameters calculated for the anti conformer using the Hartree-Fock self-consistent field procedure with a 3-21 G basis set compare well with the experimental data. The photoelectron spectrum of 1, which exhibits three peaks of different heights well separated from a smaller fourth one, can be interpreted in terms of about a 2:1 mixture of anti and gauche conformers, respectively, in the gas phase.