Elucidation of Organic Structures

Introduction

The strategy of structure determination of the organic compounds. Basic conceptions of organic structures (configuration, conformation, isomerism, tautomerism, rate processes). Organic microanalysis. Methods to determine the carbon, hydrogen and nitrogen content of the samples. Determination of the sulphur and halogen content. Qualitative and quantitative analysis of some important functional groups.

UV spectroscopy

Electronic structure of the molecules, atomic and molecular orbitals, orbital symmetry, Electronic transitions, and selection rules. Band structures. Chromophores and auxochromic groups. Discussion of some simple chromophores. Conjugation, the Woodward-Fieser rules.

Substituent, solvent and steric effects, Polyenes, aromatic and heteroaromatic structures.

IR spectroscopy

Molecular vibrations, the vibrational and vibrational-rotational spectrum. The two-atomic model, the harmonic and nonharmonic vibrations. Characteristic vibrational frequencies. The correlation between the IR and Raman spectroscopy. Stretching and bending frequencies.

The impact of the structural effects modifying the vibrational frequencies: inductive and mesomeric effects, hyperconjugation, ring strain, steric and isotope effects. Characteristic frequencies of carbonyl compounds, alcohols, amines, nitro compounds, etc. The measurement of the infrared spectra. Sample preparation. The Fourier-transform infrared spectrophotometer.

Mass spectroscopy

The mass spectrometer. Ionization methods (EI, CI, APCI, ESI, MALDI). Isotopes. Ion separation and detection methods. The coupling of the mass spectrometer (GC-MS, HPLC-MS, MS/MS). The importance of the molecule and base peak. Ion chemistry: fragmentation and rearrangement. The most important processes: alpha cleavage, onium reaction, allyl and benzyl-cleavage, McLafferty rearrangement, retro Diels-Alder reaction. Typical fragmentations and rearrangements of organic molecules. Application of isotope abundance determination: halogen compounds.

Nuclear magnetic resonance (NMR) spectroscopy

The nuclear spin. Nuclear spins in magnetic field: the Bloch equations. The measurement of the NMR spectra: CW and PFT. Spectral aquisition. ¹H and ¹³C-NMR spectroscopy. The basic NMR parameters: the chemical shift, the coupling constant. ¹H-NMR: Multiplicity and intensity of the signals. The inductive effect, diamagnetic anisotropy, ring currents. Empirical calculation of the chemical shift. The Karplus-curve. ¹³C-NMR: broadband decoupling, gated decupling. Spectral editing methods: the DEPT and the APT experiments.