Misuse of Meeting Presentation Time
letters "Cheat Sheet" as Learning Aid
To the Editor: A recent letter by Battino and Weissman [J. Chem. Educ., 50, 448 (1973)l prompts me t o relate a similar experience as a student a t the University of Oklahoma about 1952. Nearing final time, in a mathematics course emphasizing the Laplace Transform approach and the equivalence between electrical and mechanical analogs, the class thought that we must have tables of the numerous transforms and other information normally available in a "real," as opposed to an examination, environment. Our professor would not permit an open-hook examination hut he said that he would allow us to bring any information we desired on both sides of a 3 X 5-in. file card. I used a lithographer's pen and India ink, finally rendering a semester's knowledge, tables and all, into 30 in.z I took a magnifying glass to the examination; hut, much to my surprise, I didn't make extensive reference to the information. Either the professor was very shrewd (which I suspect) in devising his examination or I had leaned a great deal in preparation of the permissihle "Cheat Sheet." There are a t least two asoects of education: How to loeically and/or innovatively proceed to new and unexpecteb mnclusions and, iust as i m ~ o r t a n t .how to find and make use of what is known.
E. L. Lippert, Jr. Owens-Illinois Technical Center P.O. Box 1035 Toledo, Ohio 43666
Dihaiocarbene Reaction Hazard
To the Editor: I a m writing concerning a possible safety hazard involved in an undergraduate laboratory experiment published in the October, 1973, issue of the Journal of Chemical Education, p. 678, entitled "Dihalocarbene Addition Reaction," by S. H. Goh. We have run similar reactions to those reported with the exce~tionthat we have used henzvltriethvl ammonium chlohde as phase transfer catalysis. While the t r a.. p d n a.of dichlorocarhene is quite efficient under thereaction conditions, a small amount, approximately 790, is hydrolyzed to carbon monoxide. We have monitored carbon monoxide by ir. Nowhere in the procedure described by Professor Goh is the importance of conducting the reactions in an efficient fume hood mentioned. Nor is the production of small amounts of carbon monoxide mentioned. I thought I should bring this potential hazard immediately t o your attention. William P. Weber University of Southern California University Park Los Angeles. California 90007 21 6
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Journal of Chemical Education
To the Editor: I gave a paper a t the Chicago ACS meeting recently and listened t o many others. I am disturbed to ohserve what I hope does not become a pattern of behavior a t these meetings. I am primarily interested in chemical education. I a m a member of the Division, serve on two subcommittees. and look forward to symposia on this subject. At the chebical education meeting, however, I was disturbed when I found myself sitting through three separate papers extolling the merits of a textbook or other commercially available materials written by the speaker. This was not merely a casual allusion to a reference, a mention of a hihliography, or an aside. In two cases a t least 95% of the time was spent outlining tahles of contents, reporting on student evaluations of courses in which the textbook played a prominent part, and describing the publisher of the hook and the publishing data. In one case a single slide'was devoted to this last piece of information. When I go to a meeting I am interested in listening to papers which describe either research in chemistry, research in chemical education of a fundamental nature, or innovations in chemical education. I do not feel that my time or the time of 150 other attendants at a symposium should be squandered for what are clearly commercial purposes. Let me also make the point that none of these speakers gave any indication in the printed abstracts that our time was going to he abused in this manner. David F. Dever Macon Junior College Macon. Georgia 31206 Method for Obtain Electron Dot Structures
To the Editor: In a recent article by A. B. P. Lever (J. Chem. Educ., 49, 819 (1972)) an automatic procedure was given for obtaining electron dot structures of molecules and ions. However, Lever's method suffers from several shortcomines: (1) . , the method is unnecessarily complicated with mathematical equations that must he memorized. (2) different eauations are used depending on whether or n o t t h e species contains H atoms and/or is cyclic, and (3) the method was not applied to species in which the octet is exceeded in the simplest canonical form (e.g., SF4). A simpler, nonmathematical method of obtaining these structures is given in the W. L. Masterton and E. J. Slowinski text ("Chemical Principles," 2nd Ed., W. B. Saunders Co., Philadelphia, 1969, p. 187). However, students using this method may have difficulty in placing the combination of multiple honds and non-bonded electrons in the final step. Further, the species in (3) above and those with H atoms are not covered. Instead. one should start with the Masterton-Slowinski "skeleton structure" and add non-bonded electrons to give each atom an octet of electrons, except H. which bv virtue of its single bond, has a duet. Now, simple comparison of the number of electrons present in this "hypothetical stmcture" with the actual number of valence electrons present clearly reveals whether the hypothetical structure is the correct structure or whether multiple honds must he used or whether an octet must be expanded. Upon request I will supply any reader with a more complete description of this more general, very systematic, and non-mathematical method together with a set of instructions and examples suitable for use with students. ~
a
L. H. Berka Worcester Polytechnic Institute Worcester, Massachusetts 01609
