Our featured molecules for this month come from the paper by André J. Simpson, Azadeh Shirzadi, Timothy E. Burrow, Andrew P. Dicks, Brent Lefebvre, and Tricia Corrin (1). In the article, the authors describe the use of NMR to identify and quantify a number of components in the energy drink Red Bull, in both regular and sugar-free forms. Some of these substances—glucose, sucrose, caffeine, and methylcobalamin (vitamin B12)—are already in the JCE Featured Molecules collection, and we add twelve additional structures this month (2).
Taurine is a major constituent of bile and can be found in the lower intestine and in small amounts in the tissues of many animals and humans.
Aspartame is the name for an artificial, non-saccharide sweetener, marketed under a number of trademark names, including Equal, NutraSweet, and Canderel.
Although the NMR experiment is designed for upper-level undergraduates, Red Bull and energy drinks in general as well as several of the components of Red Bull offer interesting possibilities for study across the curriculum, starting at the pre-college level. The drink itself and component species including taurine, aspartame, and the potassium salt of acesulfame (often referred to as acesulfame potassium in that reverse nomenclature used by the drug industry) have a life of their own in the internet world of pseudo-science and urban legend. It is never too soon to begin to help students learn to navigate the pot-hole filled road that is the information highway. A discussion might begin with a simple question—“What have you heard about Red Bull?” or “What have you heard about aspartame?”. One could then proceed to explore the claims made about the health effects of these substances, and move in the direction of finding reliable information to support or refute these claims. As much as we might like our students to rely solely on the primary chemical literature as their source of chemical information, the fact is that the Internet is where almost all of them go first when researching a new topic. Of course, that is true of most of us as well, but we have the tools to separate wheat from chaff, and the majority of our students do not. If we don’t ask our students how they analyze information, we will never know what myths they continue to believe. This was recently illustrated for me in dramatic fashion when an astrophysicist colleague told me that despite his very best efforts, a number of his students in introductory astronomy still clung to doubts about moon landings.
The featured molecules this month suggest other activities. Students in introductory or analytical chemistry could be asked to measure the pH of various drinks containing citric acid or citrate ion, and to then calculate the distribution of the various citrate species at that pH. It would also be instructive to have students consider why the pKa values for citric acid (3.1, 4.8, and 6.4) are more closely spaced than those for phosphoric acid. The inositol structure that is included here is the myo-inositol isomer. Students in organic or physical chemistry could model structures of other isomers and compare their energies to this predominant form. The sulfur–oxygen bond in the acesulfame anion is quite long (177 pm) when computed using density functional theory, the B3LYP functional and a 6-31G(d,p) basis set. An interesting question would be whether or not this bond remains unusually long in other compounds where the oxygen is also part of a ring system.
Literature Cited
Simpson, André J.; Shirzadi, Azadeh; Burrow, Timothy E.; Dicks, Andrew P.; Lefebvre, Brent; Corrin, Tricia. J. Chem. Educ.2009,86, 360–362.
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