Organic Stereochemistry: An Undergraduate Exercise with Molecular Models -
A thorough understanding of stereochemistry is important for students of organic chemistry. In the author's experience, textbooks alone are inadequate to resolve all of the students' difficulties. An exercise with molecular models has, therefore, been devised to help the students grasp both the three-dimensional nature of organic molecules and conformational analysis. The exercise is undertaken by our third-year students who have already had a lecture course on the topic. The students separately complete the exercise in the lahoratary during the laboratory class. I t can be completed within the three-hour period. Fieser-type models and an octant rule model' are provided. The students are requested to draw and retain all constructions and briefly describe their conclusions in their notebooks. When the exercise is completed, eaeh student discusses it in detail with the instructor. This requires about twenty minutes. The Exercise
1) Draw and construct a model of the most stable conformation of one enantiomer of both cis- and trons-l-decalone. Show that each is chiral. 2) Deduce the configurations (R or S) of the c h i d centers in each model. 3) Deduce the sign of the 0.r.d. (c.dJ2 expected for eaeh. Consider all stable conformations. Use the octant rule modelprovided. 4) Is eis-l-decalane resolvable? Explain with models. 5) How may cis- and trans-l-deealone be intermnverted? Are they racemized in the course of this interconversion? Illustrate with models. 6) Build and draw oneenantiomer of erythro-dibromminnamicaeid.Deduce the configurations (R or S) of thechiralcenters. 7) Build and draw one enantiomer of achiral substance which does not have a chiral center. Deduce its configuration where applicable. 8) Convert a model of the open chain form of D-glucose to the most stable conformation of 8-D-glucopyranose
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Murphy, W. S., J. CHEM.E ~ u c . , 5 4 , 6 8 6(1977). W u r p h y , W. S., J. CHEM. EDUC., 52,774 (1975). Wllllam S. Murphy University College Cork, Ireland
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Journal of Chemical Education
