PHYSICAL METHODS IN ORGANIC CHEMISTRY AND LABORATORY
Learning outcomes of the course unit
Knowledge and understanding
The aim of the course is to provide students with a thorough knowledge of the most common advanced 1D and 2D NMR techniques for the structural analysis or organic compounds.
Applying knowledge and understanding
The student will be able to identify autonomously the structure of an organic compound through the interpretation of several 1D and 2D NMR spectra.
Course contents summary
Magnetic properties of nuclei: angular momentum and spin angular momentum. The Vector model. Fundamental concepts of 2D NMR spectroscopy. Relaxation processes. The Chemical exchange. The modern NMR spectrometer. Interpretation of 1D e 2D NMR spectra and determination of the structure of an organic compound.
Laboratory: Synthesis of an organic compound and its structural characterization through advanced NMR techniques.
Magnetic properties of nuclei: angular momentum and spin angular momentum. Microscopic magnetism. Correlation between magnetism and spin angular momentum.
- NMR Frequencies and Chemical shift. Linewidth and lineshape. Scalar coupling. The basic NMR experiment.
- Energy levels and NMR spectra. The spectrum for one spin. The energy levels for two coupled spins.
- The Vector model. The bulk magnetization. Larmor precession. Detection. Pulses. "On resonance" pulses. The rotating frame. The basic impulse-acquisition sequence. Calibration of pulses. The Spin-Echo experiment. Pulses of various phase. "Off-resonance" effetcs and "soft" pulses. Fourier Transformation and data processing. FID representation. Peaks linewidth and lineshape. FID manipulation. Zero filling.
- The "Product Operators" formalism. Product operators for one spin. Hamiltonians for spins and delays. Equation of motion. The spin-echo experiments with the product operators formalism. Product operators for two weakly coupled spins.
- Fundamental concepts of 2D NMR spectroscopy. 2D NMR experiments with coherence transfer mediated by J-coupling. COSY and DQF-COSY: pulses sequence and spectra interpretation. Double Quantum NMR Spectroscopy. Heterocorrelated 2D NMR spectroscopy. HMQC, HSQC and HMBC experiments: pulses sequence and spectra interpretation. 2D TOCSY NMR experiment: pulses sequence and spectra interpretation.
- Relaxation and Nuclear Overhauser Effect (NOE). The origin of the nuclear relaxation phenomenon. Mechanisms of relaxation. Correlation time. Population of the states. Longitudinal relaxation of isolated spins. Dipolar longitudinal relaxation of two spins. Cross-relaxation. Relaxation due to chemical shift anisotropy.
- NOEDif, NOESY and ROESY experiments: pulses sequence and spectra interpretation
- Coherence selection: phase cycling cycle and field gradient pulses. Order of coherence. Coherence transfer pathways. Frequency discrimination and peak shape.
- The modern NMR spectrometer. Magnet and Probe, Lock Channel, Shim and homogeneity of the magnetic field. RF synthesizer, amplifier and duplexer. Receiver and Quadrature detection. Analogue to digital convertor (ADC). Limits of digitization.
- 1D NMR spectra acquisition and processing (1H and 13C).
- J. Keeler "Understanding NMR Spectroscopy", 2nd Edition, Wiley, 2010.
- T. D. W. Claridge "High-Resolution NMR Techniques in Organic Chemistry, 2nd edition, Tetrahedron Organic Chemistry, Vol. 27, Elsevier, Amsterdam, 2009.
- N. E. Jacobsen "NMR Spectroscopy Explained: Simplified Theory, Applications and Examples for Organic Chemistry and Structural Biology, Wiley, 2007.
The format of the class will be lectures of one or two hours each spread over three mornings per week. A regular class meetings will be composed of lecture and class exercises.
The lab training will be articulated in four turns of four hours each.
Assessment methods and criteria
The final examination will include a written part in which the candidates have to assign the structure of a known organic compounds to the resonances of several 1D and 2D NMR spectra. In the following oral part, the candidates will be enquired on the theoretical topics discussed during the first part of the course.