The NMR spectroscopy in chemical research N.D. Zelinsky Institute of Organic Chemistry RAoS, The NMR Center M.V. Lomonosov Moscow Acad. of Fine Chemical Technology Higher Chemical College RAoS

(C) Ph. Toukach, 1996 Mar 16.

Course program
(theoretical part)

Chapter 1. Intro

1. NMR-related information resources. What does this course include and why.
2. NMR spectroscopy in organic chemistry. Advantages, limitations and unique opportunities of this method. The price of NMR-spectroscopic investigation.
3. Information provided by NMR spectrum: quantity of signals, their position, form and square. Examples of simplest spectra. Spectrum integration.
4. The reasons for the NMR phenomenon. Nuclei in the magnetic field and their shielding by electrons and chemical surrounding. Resonance transitions.
5. Chemical shift and its measurement units. Physical basics and idea of continuous-wave NMR experiment. What is the NMR spectrum?
6. Some important magnetically-active nuclei. Absolute and relative sensitivity. Standards of chemical shifts, TMS, chemical shift ranges for different nuclei.
7. Proton chemical shifts. Rough dependence on the neighboring atoms and bonds. Characteristic values for different structural fragments.
8. ¹³C chemical shifts. Rough dependence on the neighboring atoms and bonds. Characteristic values for different structural fragments. Additive schemes of chemical shift calculation.

Chapter 2. Spin coupling

1. The reasons for multiplicity. Spin coupling with several identical neighbors. Pascal triangle. The invariance of signal form on what sequence to split the line in.
2. Other examples of spin coupling. Various cases with three neighbors. Degeneration of DD signal into a triplet.
3. Spin coupling with nuclei with spin of 1. The isotope shift. The spectrum of real DMSO-d6.
4. Basic proton-to-proton coupling constants.
5. Spectra of 1,2,4-dibrombenzene and β-D-galactopyranose recorded on spectrometers with different frequency.
6. Examples of spin coupling: proton spectra of substituted aromatics (simple cases). Minor lines in the spectra of molecules with several chemically-equivalent nuclei.
7. Examples of spin coupling: proton spectra of substituted aromatics (complex cases). Spectra of molecules that have a symmetry plane.
8. Examples of spin coupling: how the spectra change when coupling constants in substituted benzenes are not exactly equal each to other.
9. Examples of spin coupling: the theoretical proton spectrum of allyl bromide.
10. Heteronuclear spin coupling. ¹³C satellites. The idea of broadband decoupling. ¹³C Gated experiment, its advantages and disadvantages. Dependence of coupling constants on the hyromagnetic ratio.
11. Basic proton-to-carbon coupling constants. Dependence on the hybridization state. The sign of coupling constants.

Chapter 3. Structure-to-spectrum correlation

1. Roof effect. Degeneration of two doublets into a singlet. Variants of roof effect phenomenon in the ABC spin system.
2. Examples of spectra. Aliphatic and aromatic protons. Signal overlap. Defects in line form, signal square and roof effect.
3. Proton spectra assignment using line form analysis and exact coupling constant measurement.
4. NMR spectra of mixtures. Separation of such spectra into subspectra of ingredients. Quantitative analysis of mixtures.
5. Coupling constant to structure correlation. Dependence of heminal constants on the valent angle, neighboring π-electrons and substituents. Dependence of vicinal constants on the torsion angle and bond length. Carplus equation.
6. NMR spectra of the first order and not. Theoretical and experimental spectra of high-coupled systems.
7. Dynamic effects in NMR. Temperature variations of spectra. Typical energies of widespread processes of chemical and conformational exchange. NMR response time. Signals of labile protons.

Chapter 4. Pulse NMR spectroscopy

1. The classical and pulse NMR. Limitations of continuous wave method. Short and long pulses. "Bell tuning". Fourier transformation.
2. The scheme of elementary NMR experiment. Signal/noise ratio and FID accumulation. Basic parameters of 1D NMR experiment. Relaxation delay, acquisition time. Natural and digital resolution. The spectrum window and the number of data points.
3. FID and NMR spectrum. Spin-spin and spin-lattice relaxation. Exponential decay of free induction. Lorenz line. NMR data in frequency and time domain. The real and imaginary parts of Fourier image. Signal phase.
4. The nucleus magnetic moment and the vector of macroscopic magnetization (MM). The oscillating radio-frequency field representation by precessing magnetic moments. Rotating co-ordinate frame.
5. Post-pulse MM evolution in rotating frame. Pulse types.
6. What happens if transition is not exactly in resonance with irradiation. Detecting several signals at once, blurring the MM vector into precessing components in rotating frame. The pulse diagramm for broad-band decoupling.
7. Chemical shift and coupling constants consideration within a formalism regarding vectors in rotating frame. What do FID oscillations really represent?

Chapter 5. Various NMR experiments

1. Two-dimensional correlation spectroscopy. HH COSY experiments and its pulse diagram. 2D Fourier transformation.
2. Homo- and heteronuclear COSY, structural information provided by these experiments. Proton spectrum assignment using COSY data.
3. Selective suppression of spin coupling. 1D spectra of double resonance. Partial spin decoupling. The Bloch-Ziegert shift. Examples of structural investigations with a series of double resonance experiments.
4. The reasons for spin echo. Its use for coupling constant differentiation.
5. Cross-relaxation and Nuclear Overhauser Effect (NOE). Structural dependencies of sign and absolute value of NOE. Investigation of proton spatial contacts with NOE spectroscopy.
6. Difference mode experiments. Positioning the substituents and proton spectrum assignment by difference mode NOE spectroscopy. Examples of dibromtoluene and substituted porphyrine.
7. Various NMR experiments and information they provide. The plan of NMR-assisted structural research. What does the professionalism of NMR researcher implies?
8. Homo- and heteronuclear spin correlations. Types of COSY: first pulse length variation, coherence transfer, double-quantum filter. TOCSY, HMQC, HMBC, HMQC Relay, and HMQC-TOCSY experiments and their data.
9. Other two-dimensional experiments: NOE observation (NOESY, ROESY), lability analysis (DOSY), J-spectroscopy.
10. Some notes on APT, INEPT, DEPT, SPT and similar experiments. Polarization transfer and sensitivity. Edition of ¹³C NMR spectra.

Chapter 6. Practical realization of NMR

1. Pre-FT FID processing. Weight functions, Lorenz and Gauss line. Exponential multiplication and Gauss enhancement. Zero filing, cut-off and apodization.
2. Analog signal and its digital representation. Digitizing the NMR signal. Receiver gain.
3. The principal scheme of NMR spectrometer, its control computer and I/O devices. The supercon and how it works. NMR probe heads: types, application.
4. The data excerption rate required, demands to memory volume and bit depth. Niquist criterion. Reflected signals and their phase. Why do we need a band filter?
5. The pulse phase and the idea of quadrature detection. Phase cycles.
6. What are resolution and sensitivity. Resonance condition stabilization in time and space. Gradient shims. The deuterium stabilization (LOCK). The resolution criteria: reference LOCK level, FID square, line form. Typical mistakes in shimming.
7. How to select a solvent? Sample preparation. The affect of NMR tube, sample volume, concentration and viscosity. The properties of widespread NMR solvents.
8. Redundant peak suppression in 1D- and 2D-NMR spectroscopy. Decoupler and its hardware realization.
9. Widespread NMR processing software. Spectra prediction with ACDLabs HNMR/CNMR.
10. Some notes on Bruker NMR instrument interface. Operating system, software, the experiment scheme: "shimming-acquisition-processing-output".
11. Basics of DISNMR, three jobs. Keyboard: the immediate parameter change or process start. SCM-panel: the gradual parameter change.

Supporting materials
(All files are in Russian. Press corresponding icon to download.)

	A.E. Derome "Modern NMR techniques for chemical research", Pergamon Press. (DjVu, 4.71 Mb)
	Introduction to pulse NMR (ZIPped WinWord-97 document, 1.32 Mb)
	Examples of organic chemical studies using 2D NMR spectroscopy (ZIPped WinWord-2003 document, 4.56 Mb)
	Slides used in lectures (ZIPped TIFFs, 6.06 Mb)
	control tests (ZIPped TIFFs, 790 Kb)
	NMR in natural carbohydrate research (ZIPped WinWord-97 document, 289 Kb)
	nomenclature of monosaccharides in SK2 (ACDLabs ChemSketch, 108 Kb)

Practice program

The extended practical course of NMR spectroscopy is provided by the NMR center of IOCh RAoS equiped with Bruker NMR instruments. It aims at giving students an ability to use variety of modern NMR methods at high-resolution (200-300 MHz) NMR instruments. Each group of 1-3 students is provided with 12-20 hours of qualified teaching and assistance. The NMR instruments used are Bruker AC200, WM250 and AM300.

This link opens the adapted detail description for the experiments studied within our practical course:

Ph. Toukach "Basic NMR experiments on Bruker WM/AM/AC"

Content:
• ¹H 1D NMR experiment without solvent suppression
• The special notes on solvent suppression (SSHD)
• ¹³C and other heteronuclei 1D NMR experiment special notes
• Cables connecting
• Special notes on homedecoupling (direct way, DIF, DIFSUP)
• Pulse length measurement
• Organizing the chain of NMR experiments
• H/H COSY experiment (COSY, COSY45)
• COSY RCT and RCT2 experiments special notes (COSYRCT, COSYRCT2)
• DQF COSY experiment special notes (COSYDQF)
• Special notes on solvent suppression in COSY-related experiments (COSYHG, COSYRCTG, COSRCT2G)
• 2D NOESY experiment special notes (NOESY)
• 2D ROESY experiment (ROESYW)
• {¹H-¹³C} correlation without J_CH suppression (BIRDPHPR)
• APT experiment (JMODXH)
• {¹³C-¹H} correlation (XCORRD)
• 1D NOE difference experiment (NOEDIFF)
• Multiple 1D NOE experiments (NOEMULT)
• DISNMR commands: basic, system, plot, for 2D-experiments, phase editor

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