teaching
W. ROBERT BARNARD Evergreen State College Olympia, Washington 98501
Film Reviews Structure
and S t e r e o c h e m i s t r y
Joseph Cosanova and H m l d Goldwhite. Available from Holt. Rinehart, Winston, Inc., Media Dept., Box 3670, Grand Central Station, New York, N. Y. 10017. Nine loops Super-8 technicolor cartridge. Instructors who like to use "pretty," colorful film loops will he interested in a t least previewing these films. They are up to the typical quality of highly colorful, professional films that are an the market. Some of the films are a waste of time for the student, as measured in terms of actual responses from average students currently taking organic chemistry, but others of the series afe possibly instructional materials that could serve for supplementary or self-study use. It is suggested that the instructor may wish to preview some of the films. The content of the films is quite accurate and appropriate t o the beginning organic chemistry course. There are the usual technical problems, some of which are surmounted, some not. Several of the scenes contain much too much material, particularly in terms of the 8-mm format which can accommodate no mare than 8-10 lines of printed material. See comments belaw. Insofar as learning aids are effective and convenient, this reviewer has come to evaluate educational movies on the basis of how much film could be effectively shown by slides. A silent film in which there is no motion in the scenes might as well be presented as slides which are much clearer and can be easily re-arranged to suit (maybe sometimes t w easily). A motion/static quotient (m-s) is suggested, in whieh a m-s quotient of 100 is most highly favorable to using the film media. A quotient of 15 or less is hardly worth the ticket unless this small amount of motion is truly significant to the concept. Far example, a film on atomic energy with a m-s quotient of 5 might be excellent if that 5% dealt with the mushroom explosion of an A-bomb, even though the rest of the film is static. Professional titling and artwork typically gets in the way, and this series is no exeeptlon t o the rule. The titles in film 04-80046 whieh were computer generated and notably readable is a refreshing contrast to the usual clash of colors and disregard for letter size. Drawing Structures
Part 1: 04-79964.3 min; and Part 11: 04-79980. 1.8 min.
I. After showing three types of models, ball and stick, spacefilling, and framework, the writing of formulas based on simple methane derivatives is shown. Much of the film is devoted to zooming between scenes. 11. Again, the formulas are displayed for propane and octane as superimposed formulas on framework models. An attempt to show the pitfalls of converting from 3-dimensional t o planar formulas falls short of actually helping the average beginning student. The m-s quotient for both these films is less than 10. Structural and Geometric Isomers
04-80129.2.5 min. After defining the term isomer, the two forms of C2HeO are illustrated by models and formulas. A brief list of properties leads into the conclusion that these are geometric isomers. Models and formulas show the differences between fumarie and maleic acids whieh are labelled geometric isomers. The m-s quotient is praetieally zero. Rotation and Conformation
04.80103. 3 2 min. After illustrating two kinds of madels of C2H4CI2and showing free rotation around the C-C bond. the C1-CI distances and an-
glcj are displayed. Gauche and trans farms are mptimed, nnd an animated plot of energy uf runfurmation wrrlrr tho CI -C-C-Cl angle is heautdullv portrayed. The m - s quotient is at leait 65. Conformation in Ring Compounds
04-80004. 3.4 min. The ring structures of cyelopmpane and cyclobutane are displayed, and the H-H distances, the H-H repulsions, C-C angles, and ring strain are indicated. The planar cyclobutane ring is manually twisted t o show greater stability for the puckered ring. Them-s quotient is nomore than 15. Conlormations of Cyclohexane
04-80020.3.4 mi". The planar, chair, and boat forms of cyclohexane are displayed, and the relief of strain in the planar form is shown by manually changing the planar form to the chair form. Axial and equatorial hydrogens are indicated as well as H-interactions in the boat form. Other than making the actual manual changes between these forms, there is no motion. Captions are readable. The m-s quotient is no more than 15. Energy Relationshipsol Cyclehexme Conformations
04-80046.2.0 min. The energy changes accompanying the envelope and twist intermediates between the boat and chair forms of cyclohexane are depicted graphically a t the same time that these various forms are shown. The idea of showing both the structures and the energy changes is excellent, but the 8-mm format can hardly accommodate this much material and present it in readable form. Consequently, some of the captions are unreadable. Considerable effort is needed to read the white captions on a light gray baekground and the black captions an a dark blue background. Much time is consumed in zwming and in over-fades of captions coincident to the paphical development. Again, an excellent instructional idea. but too much effort was emended in makine it Drettv rather than readable. The m-s quotient b about 70 Opflcal Isomers
04-80061.1.9 min. Models of S- and R-lactic acid are displayed, showing identical atoms, angles, and sequences. A routine minor image test and the idea of non-superimposability are briefly shown and a title quoting Kelvin on chiral structures is somewhat cluttered with Kelvin's portrait. There would have been ample space on the film to develop the concept more adequately. The m-s quotient is less than 20. Restricted Rotation around Carbon-Carbon Double Bonds
08-80087.3.5 min. ' h n s - and ck-2-hutene are compared by models, but there is a distractin8 title overlay a t one point. The properties of these two forms are displayed and then an excellent computer generated model of the r bonds is given. Rotation of the C==C bond nicely shows the r bond interactions. Unfortunately, one of the overlay titles is early when it could better have coincided with the rotation operation. The transition state is described as unstable by a static plot of the energies concerned. The m-s quotient is about 85. W. H. Slabaugh Oregon State University
Volume 51. Number 4, April 1974
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