Within a lecture on biological resolution, the synthesis of single enantiomers, and the naming and 3D visualization of omeprazole, Professor Laurence Barron of the University of Glasgow delivers a guest lecture on the subject of how chiral molecules rotate polarized light. Mixing wave functions by coordinated application of light's perpendicular electric and magnetic fields shifts electrons along a helix that can be right- or left-handed, but so many mixings are involved, and their magnitudes are so subtle, that predicting net optical rotation in practical cases is rarely simple.

Professor McBride begins by following Newton's admonition to search for the force law that describes chemical bonding. Neither direct (Hooke's Law) nor inverse (Coulomb, Gravity) dependence on distance will do - a composite like the Morse potential is needed. G. N. Lewis devised a "cubic-octet" theory based on the newly discovered electron, and developed it into a shared pair model to explain bonding. After discussing Lewis-dot notation and formal charge, Professor McBride shows that in some "single-minimum" cases the Lewis formalism is inadequate and salvaging it required introducing the confusing concept of "resonance."

The chemical mode of action of omeprazole is expected to be insensitive to its stereochemistry, making clinical trials of the proposed virtues of a chiral switch crucial. Design of the clinical trials is discussed in the context of marketing. Otolaryngologist Dr. Dianne Duffey provides a clinician's perspective on the testing and marketing of pharmaceuticals, on the FDA approval process, on clinical trial system, on off-label uses, and on individual and institutional responsibility for evaluating pharmaceuticals.

After mentioning some legal implications of chirality, the discussion of configuration concludes using esomeprazole as an example of three general methods for producing single enantiomers. Conformational isomerism is more subtle because isomers differ only by rotation about single bonds, which requires careful physico-chemical consideration of energies and their relation to equilibrium and rate constants. Conformations have their own notation and nomenclature. Curiously, the barrier to rotation about the C-C bond of ethane was established by measuring its heat capacity.

Why ethane has a rotational barrier is still debatable. Analyzing conformational and configurational stereotopicity relationships among constitutionally equivalent groups reveals a subtle discrimination in enzyme reactions. When Baeyer suggested strain-induced reactivity due to distorting bond angles away from those in an ideal tetrahedron, he assumed that the cyclohexane ring is flat. He was soon corrected by clever Sachse, but Sachse's weakness in rhetoric led to a quarter-century of confusion.

Understanding conformational relationships makes it easy to draw idealized chair structures for cyclohexane and to visualize axial-equatorial interconversion. After quantitative consideration of the conformational energies of ethane, propane, and butane, cyclohexane is used to illustrate the utility of molecular mechanics as an alternative to quantum mechanics for estimating such energies. To give useful accuracy this empirical scheme requires thousands of arbitrary parameters. Unlike quantum mechanics, it assigns strain to specific sources such as bond stretching, bending, and twisting, and van der Waals repulsion or attraction.

Professor Barry Sharpless of Scripps describes the Nobel-prizewinning development of titanium-based catalysts for stereoselective oxidation, the mechanism of their reactions, and their use in preparing esomeprazole. Conformational energy of cyclic alkanes illustrates the use of molecular mechanics.

Although molecular mechanics is imperfect, it is useful for discussing molecular structure and energy in terms of standard covalent bonds. Analysis of the Cambridge Structural Database shows that predicting bond distances to within 1% required detailed categorization of bond types. Early attempts to predict heats of combustion in terms of composition proved adequate for physiology, but not for chemistry. Group- or bond-additivity schemes are useful for understanding heats of formation, especially when corrected for strain. Heat of atomization is the natural target for bond energy schemes, but experimental measurement requires spectroscopic determination of the heat of atomization of elements in their standard states.

After discussing the classic determination of the heat of atomization of graphite by Chupka and Inghram, the values of bond dissociation energies, and the utility of average bond energies, the lecture focuses on understanding equilibrium and rate processes through statistical mechanics. The Boltzmann factor favors minimal energy in order to provide the largest number of different arrangements of "bits" of energy. The slippery concept of disorder is illustrated using Couette flow. Entropy favors "disordered arrangements" because there are more of them than there are of recognizable ordered arrangements.

After discussing the statistical basis of the law of mass action, the lecture turns to developing a framework for understanding reaction rates. A potential energy surface that associates energy with polyatomic geometry can be realized physically for a linear, triatomic system, but it is more practical to use collective energies for starting material, transition state, and product, together with Eyring theory, to predict rates. Free-radical chain halogenation provides examples of predicting reaction equilibria and rates from bond dissociation energies. The lecture concludes with a summary of the semester's topics from the perspective of physical-organic chemistry.

Continuing the discussion of Lewis structures and chemical forces from the previous lecture, Professor McBride introduces the double-well potential of the ozone molecule and its structural equilibrium. The inability for inverse-square force laws to account for stable arrangements of charged particles is prescribed by Earnshaw's Theorem, which may be visualized by means of lines of force. J.J. Thomson circumvented Earnshaw's prohibition on structure by postulating a "plum-pudding" atom. When Rutherford showed that the nucleus was a point, Thomson had to conclude that Coulomb's law was invalid at small distances.

This lecture asks whether it is possible to confirm the reality of bonds by seeing or feeling them. It first describes the work of "clairvoyant" charlatans from the beginning of the twentieth century, who claimed to "see" details of atomic and molecular structure, in order to discuss proper bases for scientific belief. It then shows that the molecular scale is not inconceivably small, and that Newton and Franklin performed simple experiments that measure such small distances. In the last 25 years various realizations of Scanning Probe Microscopy have enabled chemists to "feel" individual molecules and atoms, but not bonds.

Professor McBride introduces the theory behind light diffraction by charged particles and its application to the study of the electron distribution in molecules by x-ray diffraction. The roles of molecular pattern and crystal lattice repetition are illustrated by shining laser light through diffraction masks to generate patterns reminiscent of those encountered in X-ray studies of ordered solids.

Professor McBride uses a hexagonal "benzene" pattern and Franklin's X-ray pattern of DNA, to continue his discussion of X-ray crystallography by explaining how a diffraction pattern in "reciprocal space" relates to the distribution of electrons in molecules and to the repetition of molecules in a crystal lattice. He then uses electron difference density mapping to reveal bonds, and unshared electron pairs, and their shape, and to show that they are only one-twentieth as dense as would be expected for Lewis shared pairs. Anomalous difference density in the carbon-fluorine bond raises the course's second great question, "Compared to what?"

After pointing out several discrepancies between electron difference density results and Lewis bonding theory, the course proceeds to quantum mechanics in search of a fundamental understanding of chemical bonding. The wave function , which beginning students find confusing, was equally confusing to the physicists who created quantum mechanics. The Schrodinger equation reckons kinetic energy through the shape of . When curves toward zero, kinetic energy is positive; but when it curves away, kinetic energy is negative!

Professor McBride expands on the recently introduced concept of the wave function by illustrating the relationship of the magnitude of the curvature of the wave function to the kinetic energy of the system, as well as the relationship of the square of the wave function to the electron probability density. The requirement that the wave function not diverge in areas of negative kinetic energy leads to only certain energies being allowed, a property which is explored for the harmonic oscillator, Morse potential, and the Columbic potential. Consideration of the influence of mass reveals an "isotope effect" on dynamics, on the energy, vibration frequency, and length of bonds.

After showing how a double-minimum potential generates one-dimensional bonding, Professor McBride moves on to multi-dimensional wave functions. Solving Schrodinger's three-dimensional differential equation might have been daunting, but it was not, because the necessary formulas had been worked out more than a century earlier in connection with acoustics. Acoustical "Chladni" figures show how nodal patterns relate to frequencies. The analogy is pursued by studying the form of wave functions for "hydrogen-like" one-electron atoms. Removing normalizing constants from the formulas for familiar orbitals reveals the underlying simplicity of their shapes.

This resource is for instructors who advise any course that creates a publication - journalism, yearbook or desktop publishing.  It includes a PDF with instructions & a short video to accompany the students' learning.

This resource is for advisors of a publication - yearbook, newspaper, desktop publishing.  It contains a PDF with questions based on the hyperlinked video.

Details: This lesson can be added to 5th Grade Amplify Patterns of Earth and Sky: Analyzing Stars on Ancient Artifacts, with Lesson 2.1 after looking for patterns, making observations, and reflecting on the Model.Pursuits addressed: Identity-Students will learn about constellations from their own cultural perspectives and recognize that people from all over the world have stories related to the stars in the sky.Skills-The students will research constellations from a cultural perspective and create a class book to share with the rest of the school about constellations and their stories from around the world.Intellect-Students will interview their families to find out if their families have any constellation stories or information related to their cultures.Criticality- Students will understand that there are more than Greek and Roman names and stories for the constellations. The stories  are told and retold  by those in power.