OwlTail

Cover image of Organic Chemistry - Video

Organic Chemistry - Video

Organic Chemistry - Video

Weekly hand curated podcast episodes for learning

Popular episodes

All episodes

The best episodes ranked using user listens.

Podcast cover

30 - Esomeprazole as an Example of Drug Testing and Usage

The chemical mode of action of omeprazole is expected to be insensitive to its stereochemistry, making clinical trials of the proposed virtues of a chiral switch crucial. Design of the clinical trials is discussed in the context of marketing. Otolaryngologist Dr. Dianne Duffey provides a clinician's perspective on the testing and marketing of pharmaceuticals, on the FDA approval process, on clinical trial system, on off-label uses, and on individual and institutional responsibility for evaluating pharmaceuticals.

27 Oct 2009

Rank #1

Podcast cover

32 - Stereotopicity and Baeyer Strain Theory

Why ethane has a rotational barrier is still debatable. Analyzing conformational and configurational stereotopicity relationships among constitutionally equivalent groups reveals a subtle discrimination in enzyme reactions. When Baeyer suggested strain-induced reactivity due to distorting bond angles away from those in an ideal tetrahedron, he assumed that the cyclohexane ring is flat. He was soon corrected by clever Sachse, but Sachse's weakness in rhetoric led to a quarter-century of confusion.

27 Oct 2009

Rank #2

Similar Podcasts

Podcast cover

31 - Preparing Single Enantiomers and Conformational Energy

After mentioning some legal implications of chirality, the discussion of configuration concludes using esomeprazole as an example of three general methods for producing single enantiomers. Conformational isomerism is more subtle because isomers differ only by rotation about single bonds, which requires careful physico-chemical consideration of energies and their relation to equilibrium and rate constants. Conformations have their own notation and nomenclature. Curiously, the barrier to rotation about the C-C bond of ethane was established by measuring its heat capacity.

27 Oct 2009

Rank #3

Podcast cover

29 - Preparing Single Enantiomers and the Mechanism of Optical Rotation

Within a lecture on biological resolution, the synthesis of single enantiomers, and the naming and 3D visualization of omeprazole, Professor Laurence Barron of the University of Glasgow delivers a guest lecture on the subject of how chiral molecules rotate polarized light. Mixing wave functions by coordinated application of light's perpendicular electric and magnetic fields shifts electrons along a helix that can be right- or left-handed, but so many mixings are involved, and their magnitudes are so subtle, that predicting net optical rotation in practical cases is rarely simple.

27 Oct 2009

Rank #4

Most Popular Podcasts

Podcast cover

27 - Communicating Molecular Structure in Diagrams and Words

It is important that chemists agree on notation and nomenclature in order to communicate molecular constitution and configuration. It is best when a diagram is as faithful as possible to the 3-dimensional shape of a molecule, but the conventional Fischer projection, which has been indispensable in understanding sugar configurations for over a century, involves highly distorted bonds. Ambiguity in diagrams or words has led to multibillion-dollar patent disputes involving popular drugs. International agreements provide descriptive, unambiguous, unique, systematic "IUPAC" names that are reasonably convenient for most organic molecules of modest molecular weight.

27 Oct 2009

Rank #5

Podcast cover

28 - Stereochemical Nomenclature; Racemization and Resolution

Determination of the actual atomic arrangement in tartaric acid in 1949 motivated a change in stereochemical nomenclature from Fischer's 1891genealogical 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 conglomerates or temporary formation of diastereomers.

27 Oct 2009

Rank #6

Podcast cover

26 - Van't Hoff's Tetrahedral Carbon and Chirality

With his tetrahedral carbon models van't Hoff explained the mysteries of known optical isomers possessing stereogenic centers and predicted the existence of chiral allenes, a class of molecules that that would not be observed for another 61 years. Symmetry operations that involve inverting an odd number of coordinate axes interconvert mirror-images. Like printed words, only a small fraction of molecules are achiral. Verbal and pictorial notation for stereochemistry are discussed.

27 Oct 2009

Rank #7

Podcast cover

25 - Models in 3-D Space (1869-1877); Optical Isomers

Despite cautions from their conservative elders, young chemists like Paternó and van't Hoff began interpreting molecular graphs in terms of the arrangement of a molecule's atoms in 3-dimensional space. Benzene was one such case, but still more significant was the prediction, based on puzzling isomerism involving "optical activity," that molecules could be "chiral," that is, right- or left-handed. Louis Pasteur effected the first artificial separation of racemic acid into tartaric acid and its mirror-image.

27 Oct 2009

Rank #8

Podcast cover

24 - Determining Chemical Structure by Isomer Counting (1869)

Half a century before direct experimental observation became possible, most structures of organic molecules were assigned by inspired guessing based on plausibility. But Wilhelm Körner developed a strictly logical system for proving the structure of benzene and its derivatives based on isomer counting and chemical transformation. His proof that the six hydrogen positions in benzene are equivalent is the outstanding example of this chemical logic but was widely ignored because, in Palermo, he was far from the seats of chemical authority.

27 Oct 2009

Rank #9

Podcast cover

22 - Radical and Type Theories (1830-1850)

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. These decades teach more about the psychology, sociology, and short-sightedness of leading chemists than about fundamental chemistry, but both theories survive in competing schemes of modern organic nomenclature. The HOMO-LUMO mechanism of addition to alkenes and the SOMO mechanism of free-radical chain reactions are introduced.

27 Oct 2009

Rank #10

Podcast cover

23 - Valence Theory and Constitutional Structure (1858)

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.

27 Oct 2009

Rank #11

Podcast cover

21 - Berzelius to Liebig and Wöhler (1805-1832)

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. In their collaborative investigation of oil of bitter almonds Wöhler and Liebig extended dualism to organic chemistry via the radical theory.

27 Oct 2009

Rank #12

Podcast cover

20 - Rise of the Atomic Theory (1790-1805)

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 precise analysis was established by Berzelius, but confusion about atomic weight multiples, which could have been clarified early by the law of Avogadro and Gay-Lussac, would persist for more than half a century.

27 Oct 2009

Rank #13

Podcast cover

19 - Oxygen and the Chemical Revolution (Beginning to 1789)

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. Lavoisier's Traité Élémentaire de Chimie launched modern chemistry with its focus on facts, ideas, and words. Lavoisier weighed gases and measured heat with a calorimeter, as well as clarifying language and chemical thinking. His key concepts were conservation of mass for the elements and oxidation, a process in which reaction with oxygen could make a "radical" or "base" into an acid.

27 Oct 2009

Rank #14

Podcast cover

18 - Amide, Carboxylic Acid and Alkyl Lithium

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. More amazing than the panoply of modern experimental and theoretical tools is that their results would not have surprised traditional organic chemists who already had developed an understanding of organic structure with much cruder tools. The next quarter of the semester is aimed at understanding how our scientific predecessors developed the structural model and nomenclature of organic chemistry that we still use.

27 Oct 2009

Rank #15