Isoprenoid or terpene natural products, that seem to be made from isoprene (2-methylbutadiene), are formed by oligomerization of electrophilic isopentenyl pyrophosphate (IPP). Latex, the polymer of IPP, became commercially important when Charles Goodyear, a New Haven native, discovered how to vulcanize rubber. Statistical mechanics explains such curious properties of rubber as contraction upon heating when tightly stretched. Specific chemical treatment confers useful properties on a wide variety of polymers, including hair, synthetic rubber, and plastics.

The formation of epoxides and the regiospecificity of their acid- and base-catalyzed ring openings underlines the importance of thinking carefully about how textbooks draw curved arrows and may sometimes read too much into fundamentally inadequate experimental data. The ozonolysis of alkenes begins with several 1,3-dipolar cycloadditions that can be understood in terms of matching HOMOs with LUMOs of the corresponding symmetry. The process continues with acetal hydrolysis and either reduction or oxidation to obtain the desired product. Mechanisms of these typical reactions are analyzed.

When electrophilic addition involves a localized carbocation intermediate, skeletal rearrangement sometimes occurs, but it can be avoided when both alkene carbons are involved in an unsymmetrical 3-center-2-electron bond, as in Markovnikov hydration via alkoxymercuration followed by reduction. Similarly a reagent that attacks both alkene carbons simultaneously by providing a nucleophilic component during electrophilic attack can avoid rearrangement, as in reactions that proceed via three-membered-ring halonium intermediates.

Professor Holloway offers an introduction to the course. He explains the organization of the course and summarizes some of the key concepts that will be explored over the course of the semester. Professor Holloway uses the African American experience as a prism to understand American history, because, as he notes, the African American experience speaks to the very heart of what it means to be American. He highlights specific examples of the linkage between freedom, citizenship, and the denial of citizenship, including an ex-slave’s epitaph and Confederate scrip.

In this lecture, Professor Freedman considers the importance of the British Isles in the early Middle Ages, both in their own right and as an example of a post-Roman frontier society. In the wake of the fifth century Roman withdrawal, England experienced “radical economic simplification.” However, England’s conversion to Christianity beginning at the end of the sixth century brought about a flourishing written culture and Latin learning. Ireland experienced a similar cultural flowering, although it had converted to Christianity centuries earlier.