Youthful chemists Couper and Kekulé replaced radical and type theories with a new approach involving atomic valence and molecular structure, and based on the tetravalence and self-linking of carbon. Valence structures offered the first explanation for isomerism, and led to the invention of nomenclature, notation, and molecular models closely related to those in use today.
Professor Sylvia Ceyer covers valence bond theory and hybridization in atomic molecules. A number of examples are used to depict sp3 hybridization, sp2 hybridization, and sp hybridization.
Professor Sylvia Ceyer discusses the Valence Shell Electron Pair Repulsion (VSEPR) theory and its use with predicting the shapes of individual molecules, based upon their extent of electron-pair electrostatic repulsion. The RSEPR Rules are defined and the shapes based on VSEPR theory rationalized using atomic size and bond length.
Determination of the actual atomic arrangement in tartaric acid in 1949 motivated a change in stereochemical nomenclature from Fischer's 1891 genealogical convention (D, L) to the CIP scheme (R, S) based on conventional group priorities. Configurational isomers can be interconverted by racemization and epimerization. Pure enantiomers can be separated from racemic mixtures by resolution schemes based on selective crystallization of conglome...more
This lecture traces the development of elemental analysis as a technique for the determination of the composition of organic compounds beginning with Lavoisier's early combustion and fermentation experiments, which showed a new, if naïve, attitude toward handling experimental data. Dalton's atomic theory was consistent with the empirical laws of definite, equivalent, and multiple proportions. The basis of our current notation and of precis...more
This lecture continues the discussion of the HOMO/LUMO view of chemical reactivity by focusing on ways of recognizing whether a particular HOMO should be unusually high in energy (basic), or a particular LUMO should be unusually low (acidic). The approach is illustrated with BH3, which is both acidic and basic and thus dimerizes by forming unusual "Y" bonds. The low LUMOs that make both HF and CH3F acidic are analyzed and compared underlin...more
This is an introductory chemistry course, emphasizing basic principles of atomic and molecular electronic structure, thermodynamics, acid-base and redox equilibria, chemical kinetics, and catalysis. This course also introduces the chemistry of biological, inorganic, and organic molecules.
This is an introductory chemistry course for students with an unusually strong background in chemistry. Knowledge of calculus is recommended. Emphasis is on basic principles of atomic and molecular electronic structure, thermodynamics, acid-base and redox equilibria, chemical kinetics, and catalysis. The course also covers applications of basic principles to problems in metal coordination chemistry, organic chemistry, and biological chemistry.
Environmental Politics and Law (EVST 255) During this session, Professor Wargo stresses the importance of considering the persistence of pollutants in the environment. He continues the discussion of the Atomic Energy Commission's (AEC) risk management strategies in the wake of nuclear experiments from 1945-1963, and also introduces risk reduction strategies attempted after the nuclear explosion at Chernobyl. These strategies underestim...more
Professor Sylvia Ceyer devotes this lecture to a discussion of the periodic table, beginning with its history. Period trends are covered, including ionization energy, electron affinity, elecrtonegativity, and atomic sizes. The lecture concludes with isoelectronicity, where two molecular entities have the same number of valence electrons and the same structure, regardless of the nature of the elements involved.
This lecture begins by applying the united-atom "plum-pudding" view of molecular orbitals, introduced in the previous lecture, to more complex molecules. It then introduces the more utilitarian concept of localized pairwise bonding between atoms. Formulating an atom-pair molecular orbital as the sum of atomic orbitals creates an electron difference density through the cross product that enters upon squaring a sum. This "overlap" term is th...more
Electronegativity, metallic nature and atomic radius.