- Research Interests
- Chemistry Sudoku
T. Leon Venable
Professor and Chair, Department of Chemistry
Agnes Scott College
141 E. College Ave
Decatur, GA 30030
Introductory Chemistry (Two Semesters)
|An introduction to the concepts of chemistry and chemical behavior. The focus is on understanding
principles and not memorization. Major course topics include molecular structure
and bonding, thermodynamics, equilibrium, kinetics, nuclear chemistry and chemical reactivity. Classes include extensive use of new technologies including “clickers” to gauge
in-class comprehension of topics.
|The course focuses on the biochemistry of non-carbon based molecules and uses case studies to introduce the nutritionally essential behavior of elements such as sodium (cell potentials), iron (O2-transport and iron storage), copper (superoxidedismutase and protection against radicals) and calcium (muscle contraction and skeleton). Approximately 25 elements are known to be essential in the human diet.|
Modern Inorganic Chemistry
Chemistry remains a rapidly changing discipline in which familiar concepts such as bonding still require revision to take into account new unanticipated behaviors. Molecules previously thought to be too unstable to exist have been synthesized and characterized. This course looks at recent breakthroughs and the effect on bonding theory and chemical reactivity. The new reactivities often offer applications and uses never imagined.
The techniques that we use to effectively teach chemistry change just as the course content changes. Part of my interest includes the use of “clicker” technology in the classroom to determine student comprehension. This requires the development of multiple-choice questions that are used in class to gauge comprehension. Questions are displayed, students are given time to discuss the questions among themselves and then they are asked to commit to an answer. The results of the class response are displayed as a bar graph and we can see if we need to discuss a concept more thoroughly or move to something new. The advantage of the approach is that it allows me to modify a lecture “on-the-fly” and clarify points that are difficult. From the student perspective, it means that questions can be discussed with peers (the class is more interactive) and since answers are anonymous there is no stigma of guessing. Nothing is graded at this point.
Chemistry is also not a discipline that is viewed only on the blackboard or projection screen. It is a subject that must be experienced not only in the lab but also in lecture. I am fond of using demonstrations in the classroom to illustrate principles. Many of these may be related to daily experiences. (Why does water expand when it freezes? Aren’t molecules expected to get closer together when going from the liquid to the solid state?) Some contradict what we think we know. (Pure water does not conduct electricity.) Other observations require careful thought. (An aqueous solution of ZnCl2 conducts electricity; an aqueous solution of HgCl2 does not conduct electricity.) Some observations require that we rethink supposedly familiar definitions. (An aqueous solution of AlCl3.6H2O) is strongly acidic; an aqueous solution of Na2SO4 is basic; neutral water that is boiling does not have a pH of 7.) Demonstrations are essential to an understanding of chemistry. And besides, they are fun to do.
A goal in all of my courses is to develop an understanding of chemistry and its principles. Chemistry is not about memorization but about understanding a concept to a degree that will allow the observer to apply that concept to a completely new observation. We do not focus on memorizing the Ideal Gas Law but we do use it. At the same time we ask “Why is it referred to as an “Ideal” gas and what does that mean? Are the calculations still valid?
Exploratory Synthesis of Arene Ruthenadecaboranes
The synthesis of these new molecules is described as exploratory since the detailed reaction schemes are not known. Previous work in this lab has identified a two-step reaction sequence from commercially available reactants that we use as a starting point in the preparation of substances that may have applications ranging from cancer therapy as boron neutron capture therapy reagents to molecular electronics as low dimensional conductors.
Most of the ruthenium dimers we use and all of the final target molecules, the arene ruthenaboranes are new molecules. The bulk of our lab time is spent first trying the reaction, modifying conditions if nothing happens, isolating the products from the reactions and identifying the final, air-stable products. The reaction has “worked” when the synthesis yields the targeted molecule. The identity of the final product is determined through the use of spectroscopic techniques including gas chromatography – mass spectroscopy (GC-MS) which yields molecular mass information, Fourier transform infrared spectroscopy (FT-IR) which yields functional group information, and nuclear magnetic resonance spectroscopy (NMR) which yields the bond connectivity within the molecule. The latter is my personal favorite since it allows us to draw the first pictures of our new molecules. All of these techniques are performed on campus using departmental equipment. In the likely event that we want a detailed “picture” (actual bond angles and distances) of a new molecule the last characterization step would include single crystal x-ray diffraction. This analysis is done through collaboration with colleagues at other institutions.
1,3- or 1,4-cyclohexadiene + RuCl3.H2O —EtOH→
|[(ŋ 6-C6H6)RuCl2]2||Step 1|
B10H14 —aqueous base →
[(ŋ 6-C6H6)RuCl2]2 + B9H14- —CH2Cl2→
|6-[(ŋ 6-C6H6)Ru]B9H13||Step 3|
Preparation and Studies of Copper(II) Amino Acid Complexes
This too is an exploratory synthesis project although the actual synthesis of the copper amino acid complexes is more straight-forward than the preparation of arene ruthenadecaboranes. Historically, this project is actually an outgrowth of the ruthenaborane work. It illustrates the role of serendipity in the science lab.
The complexes that are prepared here are composed of two identical amino acids attached to one copper ion. These bis(amino acidato) complexes are not new, the first having been prepared over 100 years ago. However, the behavior of the different amino acids toward copper is quite variable and in ways that no one yet understands. In other words, using the same reaction conditions but with closely related amino acids need not yield analogous products. There is, as of yet, no obvious pattern about the role of the side chains in the formation of a particular complex. The two differences that we are focused on are: 1) the number of water molecules that are covalently bound to the copper; and 2) the particular isomer, cis or trans, that is formed.
Of greater interest is the chemical behavior of the complexes once they have been synthesized and characterized. While all of the complexes are air-stable crystals or micro-crystalline powders some have proven to be reactive in unanticipated ways. The bis(serinato) copper complex for example will undergo an unusual redox reaction under mild conditions to yield a metallic copper mirror. Our evidence indicates that even in the presence of oxygen the copper(II) will reduce in aqueous solution to yield a mirror. The generation of an electrically conductive mirror under mild conditions has obvious applications in electronic circuitry.
Less obvious is that this redox behavior has biochemical relevance since copper(II) is an essential element within the human diet. Copper(II) is known to undergo oxidation under physiological conditions including the formation of Cu(I) species.
Our research in this area is focused on both the synthesis and characterization of copper(II) amino acid complexes using previously untried amino acids and then studies of the chemical behavior, specifically the redox behavior.
Chemistry in Sudoku – The Solubility Rules: Main Group Ions
Introduction. The puzzle is composed of two parts, one based on descriptive chemistry of main group ions and the second, the popular Sudoku grid. This time the components of the grid are based on ions not numerals. Neither puzzle part is to be completed alone since some of the descriptive clues may suggest several possible answers but the Sudoku puzzle will point toward one only. As with all Sudoku puzzles the items are to be arranged in such a way that no item is repeated in any one column or one row and all nine items must be found within a 3x3 grid. To help with keeping track of the ions there is a small table after the descriptive clues in which you may record the ion identities. Happy ion hunting.