Organic Chemistry, Third Edition (Fessenden, Ralph; Fessenden, J.)

Abstract

drive access are trapped by an uncondition-al return to the Main Menu, and the Apple-soft error number (which can be looked up in the appropriate Apple manual) is printed and labelled as such. The only instance of the program "hanging" in our experience was an attempt to enter the coordinates for the 41th atom in a 48-atom structure. Because this is essentially a graphics utili-ty product, adaptation to a particular cur-riculum or institution would be relatively easy in terms of generating the shapes need-ed for a particular application, assuming availability of the necessary data. As noted, with a good set of molecular models, and with patient attention to detail, many shapes could be generated and stored on disk hy means of the internal coordinate method. Exemplary presentations of this method, and of the Cartesian technique, are presented in the tutorials. Once the tech-nique of shape generation has been mas-tered, the results are rewarding, for in addi-tion to the facilities for rotating the shape and changing its size, one can also view the shape with either the spheres (atoms) or lines (bonds) erased. Spheres are presented in three formats: small open, for hydrogen; large open, for carbon, and large filled (in-verse video) for other atoms. I t was not feasible for a review of this product to he undertaken in conjunction with a course, but a junior chemistry major, Therese Roy, graciously accepted the as-signment to test the program and to enter the data for several fairly complex mole-cules. These data came from publications by John Ricci, Chairperson of this Depart-ment, and an X-ray and neutron crystallog-rapher at Brookhaven National Laboratory. The structures used were 1. alpha-Bis(p-nitraphenyl) disulfide. 2. A polycyclic tetraoayazaphospharane. 3. A polynuclear transition metal hy-dride; [Rha(sS-CsMes)4Hd(BF4)z. 4. A tricyclic sulfur-containing polyene. Roy rapidly became proficient a t operat-ing the program. As a general rule, the Cartesian technique is easier to use for shape generation, provid-ed the necessary data are available. Puhlica-tions that provide details of crystal struc-ture often indude "positional parameters", based on the unit cell dimensions, and can he entered far shape generation via the Car-tesian Coordinate method. The Internal Coordinate procedure uses a dummy atom ($to), in order to assist the evaluation of subsequent dihedral angles. However, thesame procedure is not used for the Cartesian method, a distinction whic…