SEPARAZIONE E CARATTERIZZAZIONE DI COMPOSTI ORGANICI

Module CARATTERIZZAZIONE STRUTTURALE DI COMPOSTI ORGANICI E LABORATORIO (Modulo 2)

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The course aims to provide students with the basic knowledge and methodology necessary for the interpretation of infrared (IR), ultraviolet-visible (UV-Vis), and nuclear magnetic resonance (NMR) spectra. At the end of the course, students will be able to perform a complete structural and stereochemical characterization of organic molecules using an integrated approach with spectra (NMR, MS, UV, IR).

Laboratory activities will be dedicated to deducing the structure of an unknown organic compound through the acquisition of spectra (NMR, UV, IR) and their interpretation.

In reference to the so-called Dublin Descriptors, the learning outcomes of the course are:

D1 - Knowledge and understanding: Students must demonstrate mastery of the basic knowledge of modern spectroscopic investigation methods as well as the ability to understand the fundamental characteristics of the spectra (NMR, IR, MS and UV) of each molecule.

D2 - Applying knowledge and understanding: At the end of the course, students will demonstrate the ability to apply the acquired knowledge and the scientific method to identify a molecule through the combined analysis of spectra obtained with various techniques. Students will be able to solve structural characterization problems, even complex ones, and to simulate the spectra of new molecules. Thanks to the activities carried out during laboratory hours, students will acquire proficiency in the use of complex equipment for the acquisition of UV and IR spectra and in the processing of NMR spectra applied to the study of organic compounds.

D3 - Making judgments: At the end of the course, students will be able to interpret collected data in a coherent, critical, and correct manner, correlating them to appropriate theories. Students will be able to find information on reference spectra, physical constants, and analytical data through open access spectroscopic databases, scientific literature, etc. Students will be able to independently decide which methods are most useful for solving a particular structural problem, formulating hypotheses and discarding incorrect ones. Students will be able to evaluate the approach, possibilities, and limitations of techniques for characterizing the structure of an organic compound, critically assessing the quality parameters of the techniques used.

During laboratory experiences and exercises, students must develop organizational skills and the ability to work in groups. Students will be able to design and conduct experiments independently.

D4 - Communication skills: Students must be able to communicate clearly, both in written and oral form, their knowledge and interpretative ability of various spectra as well as the theoretical foundations underlying spectroscopic investigation techniques. When defining the structure of an organic compound, students must demonstrate and defend the correctness of their deductions using appropriate terminology and scientific representation standards, adapting the communication level to the context. Students must show they can plan and manage time, as well as interact with colleagues, both during classroom exercises and laboratory experiences.

At the end of the course, students will be able to transmit the acquired knowledge to undergraduate students in both theoretical and experimental contexts for the interpretation of 1HNMR spectra of organic compounds.

D5 - Learning skills: At the conclusion of the course, students will be able to solve a structural identification problem independently, showing the ability to approach it through the application of the competencies developed during the course.

Students will be able to easily retrieve information from specialized scientific literature, spectroscopic databases, and the internet related to analytical techniques, reference spectroscopic data, and structural characterization methodologies.

The acquired competencies will be useful for addressing complex problems, including interdisciplinary ones, related to the use of structural characterization methods.

Students will be able to independently learn new advanced spectroscopic techniques and instrumental developments, acquiring the necessary competencies to undertake future studies, address new scientific topics, or professional issues in the field of structural analysis (from academic research to industrial quality control).

Students will be able to retrieve useful information and critically interpret spectroscopic data to formulate scientifically sound responses and defend their structural proposals in different contexts, effectively communicating the results.

Information for Students with Disabilities and/or Specific Learning Disorders (SLD)

In compliance with current legislation and to ensure equal opportunities, students may request a personal meeting to plan any compensatory and/or exemptive measures, based on the course objectives and their specific needs.

English-Friendly Course Format

This course is offered in an English-Friendly format. The lessons will be primarily conducted in Italian, but international mobility students will receive comprehensive support through English-language teaching materials. Students enrolled in international mobility programs may request to take examinations in English. The English-friendly format will be implemented upon student request.

The course is structured to allow the acquisition of the indispensable tools for a straightforward interpretation of spectroscopic data aimed at the structural characterization of compounds of biological, pharmaceutical, and nutritional interest.

The course is organized into lectures, classroom exercises, and laboratory activities. The course is divided into 6 credits (CFU): 4 of frontal teaching, 1 of excercises, and 1 of laboratory.

During the exercises (1 CFU), guided analyses of IR, MS, UV, mono, and bidimensional NMR spectra will be performed to identify an unknown organic molecule. The interpretation of the spectral data is carried out by the teacher interactively with the students.

Instead, the laboratory part (1 CFU) aims to complete the training course provided by the whole class. During the hours of this part of the course, practical exercises will be developed aimed at acquiring the NMR, IR, UV and mass spectra and subsequent interpretation of the relative spectral data.

Should teaching be carried out in mixed mode or remotely, it may be necessary to introduce changes concerning previous statements in line with the program planned and outlined in the syllabus.

Basic knowledge of mathematics and physics. Good knowledge of the structure and reactivity of organic compounds.

Attendance in the course is compulsory, with the student having to attend at least 70% of the total course hours for both face-to-face

lectures and laboratory classes (see teaching regulations section 3.1)

Introduction

Importance of spectroscopic techniques in organic chemistry. Regions of the electromagnetic spectrum and corresponding spectroscopic techniques.

Ultraviolet and visible spectroscopy (UV-VIS)

Introduction and fundamental concepts. Analysis and interpretation of UV-VIS spectra: characteristic bands and absorption intensity. Main chromophores.

Exercises.

Infrared spectroscopy (IR)

Introduction and fundamental concepts. Analysis and interpretation of IR spectra. Characteristic absorptions of the main functional groups of organic molecules. Exercises.

Introduction to nuclear magnetic resonance spectrometry (NMR)

Magnetic properties of nuclei. Energy levels and population of nuclei immersed in a magnetic field. Downgrading processes. Pulse and Fourier transform NMR spectroscopy (PFT-NMR). NMR spectrometers.

1H NMR spectra

Chemical shift. Screen constant and its components. Inductive effects, diamagnetic anisotropy, electric field; effects of intermolecular relationships on the chemical shift. Protons on oxygen and nitrogen atoms. Signal intensity. Spin-spin coupling.

Scalar and dipolar couplings. Zero-order and 1st order systems. Chemical equivalence and magnetic equivalence. 2nd order systems. Exercises.

13C NMR spectra

Theory. Spin decoupling (double resonance). Broadband heteronuclear decoupling. Overhauser nuclear effect (NOE). Heteronuclear NOE. Controlled decoupling (Gated decoupling). Exercises.

1H NMR spectra and molecular structure

Equivalence, symmetry and chirality. Pairs of omotopic, enantiotopic and diasterotopic protons. Effects of a chiral centre. Virtual coupling. Coupling constants: structure and stereochemistry. Homonuclear couplings: geminal, vicinal and long-distance. Double homonuclear resonance 1H-1H. Overhauser effect difference spectrometry (NOE). Solvent effect and shift reagents. Exercises.

NMR in dynamic processes

Conformational equilibrium and chemical equilibrium. Fast exchange and slow exchange. NMR spectra at variable temperature. Eyring equation. NMR spectra of compounds containing "mobile" hydrogens.

Advanced experiments and 2D NMR

Advanced one-dimensional experiments: evolution time and mixing time. Evolution of magnetization in AX, AX2 and AX3 systems. J-modulation. DEPT Spectra. 1D-TOCSY Spectra. Two-dimensional NMR experiments (2D NMR). Homonuclear correlation spectra. Analysis of 1H-1H COSY and 1H-1H TOCSY spectra. 1H-1H NOESY and ROESY experiments and spectra analysis. Heteronuclear correlation spectra. Analysis of 1H-13C COZY spectra (HETCOR) and long-distance heteronuclear correlation 1H-13C (HMBC). Exercises.

NMR spectra of heteronuclei

15N NMR spectra: characteristics, chemical shift region, constants 1H-15N.

19F NMR spectra: characteristics, chemical shift region, constants 1H-19F. 31P NMR spectra: characteristics, chemical shift region, constants 1H-31P. Multinuclear couplings.

Protein-ligand interactions

Interactions with small ligands. Diffusion limited systems, KD, equations. Chemical exchange: slow and fast exchange. Time scales and chemical exchange. In vitro screening. Experiments for NMR characterization: WaterLOGSY, STD, DOSY.

Hints of solid-state NMR (HR-MAS NMR)

Classroom exercises

Guided analysis of spectra (NMR, MS, UV, IR); integrated use of the studied spectroscopic techniques and development of problems of determination of the structure of organic molecules.

Laboratory

Identification of unknown molecules by NMR, MS, UV and IR analysis

1. R.M. Silverstein, F.X. Webster e D.J. Kiemle, Spectrometric Identification of Organic Compounds,” John Wiley & Sons
2. A. Randazzo, “Guida pratica alla interpretazione degli spettri NMR” Loghìa Publishing
3. L.D. Field, S. Sternhell, J.R. Kalman, “Organic Structures From Spectra” IV Edizione, John Wiley and Sons (Chichester New York Brisbane Toronto Singapore)
4. M. Hesse, H. Meier, B. Zeeh, Spectroscopic Methods in Organic Chemistry, Published by Thieme
5. Educational material made available on www.studium.unict.it

The exam is intended to assess:
(a) the acquisition of the basic concepts of the course and the ability to connect them with each other and with the experiments carried out in the laboratory;
(b) the ability to clearly explain concepts using appropriate scientific language;
(c) the ability to use and quantitatively interpret experimental data by applying the concepts and methodologies learned during the course.

The final exam consists of a written test and an oral examination.
The written test, lasting 2 hours, involves the (partial or complete) resolution of a structural determination problem based on the interpretation of one- and two-dimensional NMR, MS, UV, and IR spectra.
Oral examination: assessment of the student's understanding of the course content.

If necessary, the assessment (both written and oral) may be conducted remotely via telematic tools.

The final grade will be assigned based on the following criteria:

Grade 29–30 with honors:
The student has an in-depth understanding of the theory underlying NMR, UV, and IR; is able to correctly deduce the structure of an organic molecule from spectral analysis; integrates and interprets spectra with theoretical concepts; solves complex problems independently; and demonstrates excellent communication skills and use of scientific language.

Grade 26–28:
The student has a good understanding of the theory behind NMR, UV, and IR; is able to deduce the structure of an organic molecule from spectral analysis; integrates and interprets spectra with theoretical concepts; solves complex problems with a fair degree of autonomy; and demonstrates good communication skills and language proficiency.

Grade 22–25:
The student has a fair understanding of the theory behind NMR, UV, and IR; is partially able to deduce the structure of an organic molecule from spectral analysis; integrates and interprets spectra using theoretical concepts, though problem-solving may be inconsistent; and explains concepts clearly with adequate language use.

Grade 18–21:
The student has a minimal understanding of the theory behind NMR, UV, and IR; is only partially able to deduce the structure of an organic molecule from spectral analysis; shows modest integration and interpretation of spectra using theoretical concepts; problem-solving is often non-linear; and communication is sufficiently clear, though language use is limited.

Failing grade:
The student does not possess the minimum required knowledge of the course content and is unable to deduce the structure of an organic molecule from spectral analysis. The use of scientific language is very poor or nonexistent, and the student is not able to apply acquired knowledge independently.

Sample questions: Spectroscopic analysis of organic compounds exhibiting OH groups; 1HNMR: Screen constant and chemical shift due to diamagnetic anisotropy; Proton decoupling experiments; 13C NMR: Generalities, Experiment BB and NOE effect, Off resonance; 1HNMR: Homotopic, enantiotopic, diasterotopic protons; 2D NMR: HSQC and HMBC Spectra; Prediction of NMR spectra of structural isomers; Effect of the chemical environment on chemical shifts; Characteristics of a UV spectrum, epsilon and band shift; Effect of double bond conjugation on a UV spectrum; IR spectra analysis: characteristic regions; IR theory; etc...