atomic order
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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
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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
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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.
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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
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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
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readInt() and readDouble(), The Division Operator w.r.t ints and Doubles, Order of Precedence for Operators, Type Casting, Shorthands, Constants, The Boolean Data Type, Value Comparisons, Boolean Expressions, Short Circuit Evaluation, Statement Blocks, Scope of Variables, Cascading if, The Switch Statement, The For Loop, The While Loop
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By 1950, in most of the underdeveloped world, mortality had fallen to about half its pre-modern rate. The birth rate, however, had remained high and, by 1950, was about twice the death rate. For the rest of the century, both rates fell dramatically and in parallel, maintaining the gap. The enormous excess of births over deaths in this period is known as 'the population explosion.' By 1990, the world population was growing at almost 90 mill...more
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The boom in European colonial expansion in the second half of the nineteenth century, the so-called New Imperialism, can be seen to follow from three principle factors, in ascending order of importance: religious proselytizing, profit, and inter-imperial political strategy. With respect to the latter concern, the conflicts emerging from imperialism set the stage for World War I. Along with its military and industrial consequences, imperial...more
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Part 1 - What's a Fair Start?: Rawls argues that even meritocracy—a distributive system that rewards effort—doesn’t go far enough in leveling the playing field because those who are naturally gifted will always get ahead. Furthermore, says Rawls, the naturally gifted can’t claim much credit because their success often depends on factors as arbitrary as birth order. Sandel makes Rawls’s point when he asks the students who were first born i...more
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The focus of the lecture is simple harmonic motion. Professor Shankar gives several examples of physical systems, such as a mass M attached to a spring, and explains what happens when such systems are disturbed. Amplitude, frequency and period of simple harmonic motion are also defined in the course of the lecture. Several problems are solved in order to demonstrate various cases of oscillation.
