Curious kinetic orders can be mechanistically informative. Fractional kinetic orders suggest dissociation of a dominant aggregate to give a smaller reactive species. An apparent negative kinetic order, due to competition with a second-order process, leads to spontaneous deracemization of chiral crystals. Changes in bond dissociation energies can be due to differences in bonds or in radicals.
This second semester of Freshman Organic Chemistry builds on the first semester’s treatment of molecular structure and energy* to discuss how reaction mechanisms have been discovered and understood. It also treats the spectroscopy and synthesis of organic molecules. Reactions and their rates can be understood in terms of reaction-coordinate diagrams involving the passage of a set of atoms through the “transition state” on the potential-energy surface. Analysis of bond-dissociation energies suggests a chain mechanism for free-radical halogenation of alkanes. Experimental determination of
Professor Freedman opens by discussing why historians use the writings of Procopius and Gregory of Tours, a sixth century bishop whose history of the Merovingian kings is discussed the following week. Procopius’s three works – The Wars, the adulatory Buildings, and the invective Secret History – are the best sources on the reign of the Emperor Justinian. Under Justinian and his wife Theodora, the Roman Empire reached its height as it reclaimed territories in North Africa and Europe previously lost to the Vandals, Visigoths and Ostrogoths..
Professor Freedman focuses on the question of how the Eastern Roman (Byzantine) Empire survived, while the West collapsed in the fifth century. He begins with a brief overview of Procopius’ Secret History, a work which presents a highly critical account of the reign of the emperor Justinian.
In this lecture, Professor Freedman considers the various barbarian kingdoms that replaced the Western Roman Empire. Oringinally the Roman reaction to these invaders had been to accommodate them, often recruiting them for the Roman army and settling them on Roman land. Now, however, they were the rulers of the previously Roman lands of the West. These tribes included the Ostrogoths and Visigoths in Italy, the Franks in Gaul, and the Vandals in North Africa. As most sources about these groups come from the Roman perspective, it’s unclear how coherent each group was.
The Roman Empire in the West collapsed as a political entity in the fifth century although the Eastern part survived the crisis.. Professor Freedman considers this transformation through three main questions: Why did the West fall apart – because of the external pressure of invasions or the internal problems of institutional decline? Who were these invading barbarians? Finally, does this transformation mark a gradual shift or is it right to regard it as a cataclysmic end of civilization?
Stability in the ocean is based on the density of the water. Density must increase with depth in order for the ocean to be stable. Density is a function of both temperature and salinity, with cold salty water having a higher density than warm fresh water. Temperature and salinity in the ocean can be affected by the atmosphere. Heat can be added to or removed from the ocean, and precipitation and evaporation change the salinity of the ocean. Surface winds also act as a forcing mechanism on the ocean by creating a wind stress forcing which pushes surface waters.
Plate tectonics and ocean bathymetry are discussed. Bathymetry is the study of ocean depth, which is affected in some regions by plate tectonics and mantle dynamics. Mid-ocean ridges are formed at plate boundaries where mantle material is rising to the ocean crust and solidifying as it cools to form new ocean crust material. Seamounts are volcanoes that have formed from molten mantle material pushing up through the ocean crust, but these volcanoes lie below sea level. These features are measured using acoustic depth profiling.
The seasonal cycle on Earth causes shifts in the bands of precipitation in the northern and southern hemispheres. The polar front shifts between high and mid-latitudes which causes a latitudinal shift in the occurrence of frontal cyclones. The Intertropical Convergence Zone also shifts across the equator bringing bands of precipitation to different tropical regions throughout the year. Regional climates on Earth have been classified based on temperature and precipitation values. Areas affected by seasonal shifts in the ITCZ and polar front are included in this classification scheme.
There are several factors that impact climate on Earth. Different areas on Earth have different climates depending on factors such as their latitude and surrounding terrain. Maps of annual average precipitation illustrate these variations in climate. Continentality also affects climate based on the ability to change temperatures on land versus in the oceans and also the imbalance of land mass between the northern and southern hemispheres. Seasonality is a dominant factor in climate.
