Work by Wöhler and Liebig on benzaldehyde inspired a general theory of organic chemistry focusing on so-called radicals, collections of atoms which appeared to behave as elements and persist unchanged through organic reactions. Liebig's French rival, Dumas, temporarily advocated radicals, but converted to the competing theory of types which could accommodate substitution reactions.

The most prominent chemist in the generation following Lavoisier was Berzelius in Sweden. Together with Gay-Lussac in Paris and Davy in London, he discovered new elements, and improved atomic weights and combustion analysis for organic compounds. Invention of electrolysis led not only to new elements but also to the theory of dualism, with elements being held together by electrostatic attraction. Wöhler's report on the synthesis of urea revealed isomerism but also persistent naiveté about treating quantitative data.

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.

This Midterm Exam covers the second quarter of the course.

This lecture begins a series describing the development of organic chemistry in chronological order, beginning with the father of modern chemistry, Lavoisier. The focus is to understand the logic of the development of modern theory, technique and nomenclature so as to use them more effectively. Chemistry begins before Lavoisier's "Chemical Revolution," with the practice of ancient technology and alchemy, and with discoveries like those of Scheele, the Swedish apothecary who discovered oxygen and prepared the first pure samples of organic acids.

This lecture completes the first half of the semester by analyzing three functional groups in terms of the interaction of localized atomic or pairwise orbitals. Many key properties of biological polypeptides derive from the mixing of such localized orbitals that we associate with "resonance" of the amide group. The acidity of carboxylic acids and the aggregation of methyl lithium into solvated tetramers can be understood in analogous terms.

Continuing the examination of molecular orbital theory as a predictor of chemical reactivity, this lecture focuses on the close analogy among seemingly disparate organic chemistry reactions: acid-base, SN2 substitution, and E2 elimination. All these reactions involve breaking existing bonds where LUMOs have antibonding nodes while new bonds are being formed. The three-stage oxidation of ammonia by elemental chlorine is analyzed in the same terms. The analysis is extended to the reactivity of the carbonyl group and predicts the trajectory for attack by a high HOMO.

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 underlining the distinction between MO nodes that derive from atomic orbitals nodes (AON) and those that are antibonding (ABN).

Professor McBride begins by using previous examples of "pathological" bonding and the BH3 molecule to illustrate how a chemist's use of localized bonds, vacant atomic orbitals, and unshared pairs to understand molecules compares with views based on the molecule's own total electron density or on computational molecular orbitals.

This lecture brings experiment to bear on the previous theoretical discussion of bonding by focusing on hybridization of the central atom in three XH3 molecules. Because independent electron pairs must not overlap, hybridization can be related to molecular structure by a simple equation. The "Umbrella Vibration" and the associated rehybridization of the central atom is used to illustrate how a competition between strong bonds and stable atoms works to create differences in molecular structure that discriminate between bonding models.