chemistry courses. A useful device is to illustrate the stmcture of trinitroglycerine along with that of 1,3-diphosphoglycerate, a hieh enerw comoound formed durinr the breakdown of a resemblance bein t& body: Students readily tween the molecules. The reoutation of nitroglvcerine for explosively "producing" eneigy is common knowledge. A comment that both nitrogen and ~hosphomsare in the same column of the Periodic ~ k h l and e havk chemical similarities is usuilllv sutlicient tn convince skepticd listeners that organic are capahle of storing and releasing metabolic energy. I t is necessary to emphasize that only the anhydride phosphate bond containing compounds &e energy-rich; otherwise students will incorrectly expect various hexose and triose phosphates in the glycolytic pathway to he high-energy molecules. Once the concept of high-energy phosphate has been imparted by the parallel between organic nitrates and phosphates, reference to an accepted explanation for this biochemical property is appropriate. A good follow-up uses total possible resonance forms as outlined and argued by Oesper (Arch. Biochem., 27,255 (1950)).
note
An Organic Lab Practical in Library Resources J o h n F. Rosen and Deborah Meeder Nycz Broward Community College Pompano Beach, Florida 33063 We have designed an exercise which gives students experience in the utilization of various resources that wouldordinarily be found on reserve in our library. Students are required to include information in their lab write-ups regarding the physical constants of all of their reactants, reagents and products, and usually do not rely on these resources beyond the table of physical constants. For this reason, we designed our lab practical so that the students would gain greater appreciation of the myriad of information contained in the resources. Each student was given a list of five questions, selected from a hnnk of 120 questions, and a handout descrihing the types
578 I Journal of Chemical Education
of information contained in the references thev would beusine to answer the questionn. The references used were "Lange's Handbook of Chemistw." "The Handbook of Chemistrv and Physics," "The ~ e r c k i n d e x , ""The Condensed ~ h e k c a l Dictionarv." and the "Aldrich Cataloeue." The questions are varied and deal &h topics which range from the correct method of disoosal of an organic comoound to the analytical composition i f a food prod&t. ~om'of the auestions are humorous due to their obscuritv, and provide challenge to the students in their search. ~ s a m p f set e of questions follows
a
In what form does one purchase see-hutyllithium and what is the proper method of its disposal? What is the dissociation constant for novocaine? What is the maximum allowable concentration of zinc in drinking water? What is the diamagneticsusceptibility of coronene? What is the half-lifeof ZBMg? This practical has been presented to students during a lab class. The resources are nresent and availahle for student use while they are waiting for a particular reaction to reflux, distill ur cool down. This fills ur, what mirht otherwise be ronsidered free time and allows f& interes&ng exchange between students. Reaclion to this practical has been favorable and students are renerallv amazed at the diversity of information contained in &e reso&es. The list of questions is available upon request.
Compact Compact Gregory V. Nelson of Drew University in Madison, New Jersey points out that an instructive model showing the rigidity of the helical folding pattern and the flexibility of a non-helical region in a protein can be constructed from a cardboard mailing tube. At the center of the length of the tube, carefully cut along the helical seam for about one revolution. Simply twist the two ends of the tube to unfold the helix and to bend the remaining helical regions back toward each other. For demonstration purposes, have also an intact mailing tube a t hand to show the original rigidity.
