JOURNAL OF CHEMICAL EDUCATION
A MOLECULAR-MODEL EXAMINATION IN ORGANIC CHEMISTRY FLOYD L. JAMES Miami University, Oxford, Ohio
MOST teachers of organic rhemistry use molecular models as instructional aids. Display, inspection, and occasionally construction by students are the usual techniques employed. This note reports a successful scheme for making use of models in an examination. Models of from eight to ten organic compounds, each identified by a number, are arranged on laboratory benches or on the tablet arms of chairs in approximate order of increasing difficulty. Each student is given an answer sheet on which there is a statement of the element represented by each color used. The first student is started on the first model and given one minute to identify it. At the signal "move" he moves to the second model and the second student begins on the first. This is continued until the last student has scen the last model. A student is allowed only two minutes extra time after he has left the last model. Models of the stick-and-hall type are used to emphasize structural relationships, but several Fisher-
Hirschfelder compact type models are always included to illustrate better the real shape of the molecules. Cis and trans forms may be used if stereoisomerism has been studied. At the midpoint of a first organic course recognition of functional groups and simple alkyl and aryl radicals should be regarded as satisfactory achievement. Dimethyl aniline and succinic anhydride are compounds about as complicated as can be used successfully. Models of compounds more complex than these usually require conversion to structural formulas before identification. This is undesirable. The announcement that a test of this type is to be given stimulates students to become familiar with molecular models. Their study of models and the test itself help give them a three-dimensional idea of molecules. Using 30 minutes of laboratory time for such a test has seemed worth while in helping to bridge the gap in student's thinking between blackboard and test tube.
