SYNTHESIS AND TECHNIQUES IN ORGANIC CHEMISTRY
Learning outcomes of the course unit
To increase the knowledge in the field of organic stereochemistry and to acquire experience in the synthesis and characterisation of (chiral) organic compounds.
Course contents summary
Effects of magnetic field intensity on 1H NMR spectra. Partitioning equilibria. Signals of diastereotopic protons. Study of dynamic phenomena by NMR spectroscopy. Time scale in NMR, IR and UV spectroscopies. Coalescence temperature. Conformational analysis by NMR: thermodynamic and kinetic aspects.
Stereoisomer properties. Chiral discrimination. Homochiral and heterochiral interactions. Different kinds of racemic mixtures. Physiscal properties of racemic mixtures and single enantiomers. Diastereomeric discriminations. Origin of chirality in nature. Chirality and biological effects. Stereoisomers due to axis, plane of chirality and elicity.
Determination of enantiomeric composition.
Chirooptical methods. NMR methods (chiral derivatizating agents, chiral solvating agents, lanthanide shift chiral agents). In particular, determination of enantiomeric excess of chiral alcohols by drivatization with Mosher acid and attribution of absolute configuration by 1H NMR spectroscopy. Chromatografic methods (solid-liquid chromatography on chiral stationary phase, gas-chromatography on enantioselective stationary phases, HPLC involving chiral stationary phase or chiral eluant).
Resolution of racemic mixtures: crystallisation. Chemical separation with diatereoisomer preparation. Kinetic resolution. Enzymatic resolution.
Determination of absolute and relative configuration.
Stereoselctivity in aldolic condensation involving achiral reagents.
1) Synthesis of deuterated compound: 2-d cynnamic acid.
2) Synthesis of 8-methoxy-3-carboxycoumarin in heterogeneous catalysis.
3) Synthesis of N-acetyl-(L)-prolyl-(L)-fenylalanine methyl ester and conformational study by dynamic 1H NMR. Characterization by polarimetric and circular dichroism measurements.
4) Enzimatic enantioselective reduction of trifluoroacetophenone and enantiomeric excess determination by GC employing a chiral column.
5) Derivatization of the chiral alcohol with Mosher acid ; determination of the enantiomeric excess and of the absolute configuration by 1H NMR spectroscopy.
6) Study of the stereoselectivity in the aldolic condensation reaction under kinetic or thermodinamic control.
E.L. Eliel, S.H. Wilen “Stereochemistry of Organic Compounds” J.Wiley & Sons, 1994.
G.F. Pedulli “Metodi fisici in Chimica Organica Piccin”1996.
R. M. Silverstein, G. C. Bassler, T. C. Morril “Spectroscopic Identification of Organic Compounds” J.Wiley & Sons, 1991 5th Edition (esiste anche la versione in italiano R. M. Silverstein, F. X. Webster “Identificazione spettroscopica di composti organici, Casa Editrice Ambrosiana 1999)
E. Juaristi “Stereochemistry of conformational analysis” J.Wiley & Sons, 1991