Grad~bookEditing This area of the system allows the inI directly with the structor, through a terminal, ~ I interact stored gradebooks for editing, grade entry, and many other purposes. A total uf 31 commands are availahle. Grades and stored student information mav he entered, chaneed, or observed. The addition, deletion, or transferring of students from one section to another may he done. Extra Iahoratuw sections may he opened during the semester. After editing, instructor and/or student gradebooks may be printed on the computer line printer. At the end ofthesemester, final averages are calculated and printed on the line printer in a final gradebook which serves as the end-of-semester record and can he kept for future reference after assigning course grades. Due to the large number of commands, a "help" command is included. When help is requested for a command, information on how and why to use that command is printed on the terminal screen. Data-Base Clpdofing. This final area consists of a series of interactive oroerams that allow the instructor to make chances . . in the various data hases used by the system. These include the literature values for the physical properties, system security codes, and professor and section names. This system has been designed so that once it has been set up on a computer it requires very little operator attention despite the extensive duties it performs. For security reasons no complete copies of this program system will he made availahle. However, turther information and details on specific capabilities, functions, and programming and security techniques, including a longer version of this paper, will be provided upon request in order to assist in the development of other similar program systems.
Isomers of Octahedral Coordination Complexes Richard Cornelius Wichita State University Wichita. KS 67208 The comprehension of the spatial orientation of ligands about a metal ion is fundamental to an understanding of many topics in coordination chemistry. The teaching of stereochemistrv. however. often suffers from the limitation of the two-dimensiunal media typically used in the classroom. Molecular models are an ohvlous t e a c h i n ~aid, but they do little to help students deal with the two-dimensional s~tructures found in hooks and in the literature. The program described here is designed to bridge the gap between two-dimensional and three-dimensional representations by allowing studentcontrolled "rotation" of complexes presented on the twodimensional screen fare in typical textbook fashion. Octahedral complexes have been chosen for treatment on the basis of their ahondance in coordination chemistry and the variety of types of isomerism that occur for this coordination geometry. Two octahedral structures are oresented on the microcomputer screen with the same randomly chosen set of six ligands as shown in Figure 5. Some ligands may occur more than once. The structures may he isomers or may he identical and differ only in orientation. Students are asked to conclude whether the two structures are geometrical isomers, enantiomers, or identical. Before reachine a conclusion, users may opt. to rotate one of the structures a h ) u t the x , y , or z axis in 90' increments as many times as desirable. In this fashion users may try to place the structures in the same orientation to show whether they are identical or may try to orient one as the mirror image of the other in order to relate enantiomers. After a student reaches a conclusion and types it in, the computer will report whether the selection is correct. If the student is in error, the program returns to the rotation mode 552
Journal of Chemical Education
H r e t h e s t r u c t u r e s shown enant lomers g e o m e t r l c a 1 isomers o r identlca l ? ' Pespond E,G, or 1 . I
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Figure 5. Representative screen display from program aiding students in learning to distinguish isomers of octahedral coordination complexes. and the student is given another opportunity to rotate one of the structures in order to understand the errur and reach the correct conclusion. This program has been used in senior inorganic chemistry and has met an enthusiastic response. The program is selfcontained in that complete instructions for its use are presented on the screen. The algorithm used to determine the isomeric relationship amonc the randomlv eenerated structo ensure an appropriate mix of enantiomers, geometrical isomers, and identical pairs of structures and to make apparent to the user the 1-2 sec delay required to generate and internally identify the structures. Audio signals are used to augment the video display. The program is written for P E T 2N1-8 microcomputer and for the Apple I1 plus. The coding uses 170 lines of Microsoft BASIC (Applesoft for the Apple) and the program operates within a limitation of 8K RAM. The routine could he rewritten with relative ease for other versions of BASIC. The heart of the program is the isomer generation and identification and should he transferrahle with little change; few string operations are used. The " eranhical oortions ofthe . nroeram would . =. require more extensive adaptation, but they constitute only a small portion of the oroeram. An annotated listine. PETauthor. Send check or money eider to R. D. Cornelius, Department of Chemistry, Wichita State University, Wichita, KS 67208 ($1.00 for listing, $12.00 for P E T cassette, $15.00 for Apple diskette).
Interactive Computer Program System for Plotting Molecules and Crystal Structures M. L. Dheu and S. Perez' Centre de Recherches s u r les Macromol6cuies V(tg6tales (C.N.R.S.):' 53X. 38041 Grenoble C6dex. France
Students in organic chemistry usually have difficulty in visualizine molecules in three dimensions. When dealine" with a fairly simple molecule any space-filling model is useful. However. three-dimensional comolex molecular interactions. polymeric structure, and/or crys& packings can be envisaged convenientlv onlv throueh the use of comouter eraohics. At . the present time, most ofthe available drawing programs have been designed to he run on large computers and, on the average, are not timesharing-oriented. Usually several trials are necessary to obtain a satisfactory drawing. One way to improve this state of the art is to run a timesharing-oriented set of programs on a dedicated minicomputer. We have developed an interactive computer program system, PITMOS, (PIT-
' TO whom correspondence should be addressed.
* Laboratoire propre du C.N.R.S., associe 6 I'Universit6 Medicale
et Scientique de Grenoble
I'AKIND, hut input desrrihinp crystall
