Academic Year 2021/2022
Free text for the University
- Teaching style
- Lingua Insegnamento
|[60/68] PHYSICS||[68/40 - Ord. 2020] FISICA MEDICA E APPLICATA||6||48|
|[60/69] CHEMICAL SCIENCES||[69/00 - Ord. 2019] PERCORSO COMUNE||6||56|
Knowledge and understanding: at the end of the course, the student will know the main multi-pulse techniques for the acquisition of one-dimensional spectra, the fundamental acquisition parameters and the criteria for a correct setup. The student will learn how to interpret nuclear magnetic resonance spectra of medium complexity and how to study the relaxation times. At the end of the course, the student will understand the fundamental physical principles of the technique through their description at different levels, i.e. the classic vector model and the energy levels diagram.
Knowledge application ability: at the end of the course, the student will be able to use previous knowledge in the different fields of Chemistry in order to solve problems and answer scientific questions by applying nuclear magnetic resonance spectroscopy.
Judgment capacity: the course aims at training the student in problem solving in the context of scientific studies through nuclear magnetic resonance spectroscopy. The final goal is to make the student independent in taking decisions pertaining to the choice of the most appropriate approach for the given problem.
Communication skills: the student will be able to integrate concepts in a coherent framework and to express them appropriately, concisely and effectively in a talk and through the use of diagrams, graphs and formulas.
Learning skills: the student will acquire the ability to move between different and complementary models for the definition / description of concepts and phenomena. The student will be continuously encouraged to use alternative sources, not only books, but also videos, graphic softwares, databases, etc ...
It is important that the student is proficient in Chemistry. In addition, a good background of Physics and Mathematics is absolutely necessary, especially on trigonometry.
Module 1. Fundamentals:
- Brief historical report on the technique’s development
- Nuclear magnetic moment
- Spin energy levels
- Larmor precession
- Population difference and sensitivity
- Spectrometer architecture
- Delay-Pulse-acquisition sequence
- The rotating reference frame
- The (hard) radio-frequency pulse
- Signal detection system in brief
- The FID (free induction decay)
- The resonance’s offset
- The various NMR scales
- The Fourier transform in brief
- The quadrature detection in brief
- Nuclear spins longitudinal and transversal relaxation
- The chemical shift (origin and interpretation)
- Scalar coupling among nuclear spins (origin and relationship with molecular structure)
- Relative sensitivity and isotopic abundance
- First and second order spin systems and their spectra
- Chemical and magnetic equivalence
- Effects of field-strength over sensitivity and resolution
- Spectral phase correction
- Probe tuning and matching
- The lock feedback loop
- Shimming the field
- Choice of the solvent
- Choice of the reference substances (frequency and pH)
- Choice of the buffer
Module 2. Relaxation and multi-pulse techniques:
- Transversal relaxation time determination: the spin-echo sequence
- The T2 filter
- Longitudinal relaxation time determination: the inversion-recovery sequence
- Relaxation time and molecular motions
- Relaxation mechanisms (dipolar interaction, chemical shift anisotropy, quadrupolar electric moment)
- Isotopomers and relative sensitivity
- The decoupling (selective and broad-band)
- Solvent suppression (presaturation)
- The NOE (Nuclear Overhauser Effect)
- The steady-state NOE difference experiment
- The J-modulated spin-echo sequence
- Sensitivity optimization
- The APT sequence (Attacched Proton Test)
- Polarization transfer
- The INEPT sequence (Insensitive Nuclei Enhanced by Polarization Transfer)
- The refocused-INEPT
- The DEPT sequence (Distorsionless Enhancement by Polarization Transfer)
The course provides 6 CFU, among which 4 CFU of lectures and 2 CFU of practical activities with a total of 56 hours. The course is planned as two consecutive modules: i) fundamentals and ii) relaxation and multi-pulse techniques. Each module comprises several series of lectures where topics will be proposed by following increasing complexity. We will start from the phenomenological picture and, then, we will move on with the mathematic quantitative description. Each topic will be completed by examples of practical applications and by providing food for thoughts about other possibilities and potential uses as well as limitations. Finally, each topic will end with a series of guided exercises in the class, where students will be asked to face and solve different problems, aiming at verifying and consolidating the information and the new concepts presented during the lectures. Exercises will be always accompanied by discussion with the class, in order to encourage and develop the critical and analytical skills of students. At the end of the first module, one laboratory day is planned, where the student will have the chance to interpret real spectra to deduce the molecular Lewis structure and to consolidate the knowledge of the topics touched so far.
Due to the present epidemiologic situation, there will be the possibility for the lectures to be attended both in class and in web streaming, with automatic recording which will be made available to the students. Exercises will be possibly carried out through the available software and electronic devices.
Verification of learning
The examination will be a written test and the colloquium.
Positive result of the written test is necessary to get access to the colloquium.
Exercises aim at verifying the acquired competence, in terms of
- making logic connections among the different topics
- problem-solving capabilities related to practical applications of NMR spectroscopy.
The final colloquium aims at verifying
- knowledge from a theoretical viewpoint about the chemico-physical phenomena behind practical application of NMR spectroscopy
- capacity of presenting the topics in a concise and comprehensive way
- capacity of moving forward for future studies and for professional purposes.
Written examination comprises series of TRUE/FALSE questions, multiple-choice questions and short answers, graphical/numerical exercises. In addition, two molecular formulas will be submitted together with the corresponding NMR spectra. The student will be asked to deduce the right Lewis structure of the corresponding compounds.
The final colloquium requires the use of graphics, equations, schemes, flux diagrams, and so on. By starting from general aspects and then moving to specific details, the student will be asked to move from the basic concepts presented during the course to proceed through the different topics in details.
Marks and final evaluation:
The conclusive mark will be assigned as a fraction of 30 (x/30) and it will be given by the average of the mark gained from the written exam and the colloquium.
The mark (x/30) of the written exams will be given by the weighted average of the grade obtained in the section of questions/exercises and the section of spectra interpretation.
In details, questions/exercises section will be evaluated as follows:
(number of right answers / total number of questions-exercises) * 30
Spectra interpretation: 0-5 points will be assigned to each of the two submitted cases. The evaluation will be then obtained as:
((points for case 1 + points for case 2 + 1)/10) * 30
Finally, the overall mark will be calculated as:
(2/3)*(mark of section 1) + 1/3*(mark of section 2)
Minimum evaluation to get access to the colloquium: 18/30.
Maximum evaluation: 30/30.
The mark to the final colloquium will take different factors into account:
a) Ability of oral and graphical communication
b) Scientific language
c) Contents knowledge
d) Ability in correlating notions
Consequently, the final mark can be (x/30):
- Sufficient (18-20) Modest communication abilities. Little acquisition of knowledge, superficial level, many gaps.
- Moderate (21-23) Acceptable communication abilities. Moderate acquisition of knowledge but lack of expatiation, few gaps.
- Good (24 to 26) Satisfactory communication abilities. Rather large wealth of knowledge, moderate in-depth, small gaps. Critical spirit and logical linking capability are clear.
- Outstanding (27-29) Remarkable communication skills. Extensive wealth of notions, high in-depth, marginal gaps. Synthesis ability and competence are clear.
- Excellent (30) Excellent communication skills. Very extensive and in-depth knowledge, irrelevant gaps. Competence and deductive skills are clear.
The praise is attributed to the candidates clearly above average, and whose notional, expressive, conceptual, logical limits, if any, as a whole are completely irrelevant.
T. Claridge “High-Resolution NMR Techniques in Organic Chemistry”, Elsevier ed.
N.E. Jacobsen, “NMR Spectroscopy Explained”, Wiley ed.
J. Keeler, “Understanding NMR Spectroscopy”, Wiley ed.
R.M. Lynden Bell, R.K. Harris, “Spettroscopia di Risonanza Magnetica Nucleare”, Ambrosiana ed.
J.W. Akitt, B.E. Mann, “NMR and Chemistry: an introduction to modern NMR spectroscopy”, Cheltenham : Stanley Thornes ed.
The slides projected during the lectures will be provided. Format will be low resolution pdf. They are merely intended as a study guideline. Slides are neither to be considered as alternative nor additional to the suggested text books in any way. The numerical exercises proposed during the lectures will be also provided in pdf format, together with the solution, the solving method and comments.