Department of Chemistry College of Science Sultan Qaboos University Title : CHEM 3326 (Applied Spectroscopy) Credits : 3 Course Format : 2 lectures and 2 tutorials Course Text : Spectrometric Identification of Organic Compounds, Silverstein & Webster, Sixth Edition, John Willey and Sons. Organic Structures from Spectra (L.D. Field, S. Sternhell and J.R. Kalman, 2 nd Edition, John Willey) Grading Scheme : Two Mid Term Exams: 50 %; Final Exam: 50 % Course Description: This course introduces the basic principles and applications four spectroscopic techniques - IR, UV, Mass and NMR ( 1 H and 13 C) - widely used in the structure analysis of organic molecules. The lecture hours will cover up the basic theory as well as the interpretational aspects. The tutorial sessions are designed in such a way to develop the interpretational skills of the students. Unit 1. Mass Spectrometry and Basic principles and Instrumentation Learn the basic theory and setup of low and high resolution mass spectrometers. Ionization methods Know about various ionization methods such as Electron Impact Ionization (EI), Chemical Ionization (CI) and FAB ionization for producing mass spectrum. Recognition of the Molecular Ion Peak Learn to recognize the molecular ion peak in various mass spectral techniques Use of Mol. Formula and Index of Hydrogen Deficiency Know how to use index of hydrogen deficiency in order to determine the degree of unsaturation in a compound. 1
Nitrogen rule Common types of fragmentation in EIMS Know how to apply the nitrogen rule in order to eliminate some molecular formulae and narrow the list to one or two. Learn to identify the characteristic fragment ions in the EI mass spectra of various chemical classes. common types of fragmentation in some chemical classes such as hydrocarbons, alkenes, aromatic compounds, hydroxycompounds, carbonyl compounds, amino and nitro compounds and halogen compounds. Know the common types of fragmentations in EI mass spectrum Learn to identify rearrangement ions and fit them into a possible structural formula. Learn to piece together fragments to get to the greater picture of the structural formula. Learn to use mass spectrometry in conjunction with infra red and NMR spectroscopy to determine the exact structure of the exact isomer Unit II. Infrared Spectroscopy Basic theory and instrumentation Know the basic theory and instrument design. Know about various types of stretching and bending vibrations of bonds in molecules. Group frequency region and Fingerprint region in IR spectrum. Functional group/s identification from an IR spectrum Use of correlation charts. Know the different regions of the IR spectrum and learn how useful information about the molecular structure can be gathered from characteristic bands Learn to recognize the functional group/s in a molecule from the diagnostic bands Learn to use correlation charts to interpret a spectrum Know how to combine IR data with other spectroscopic data in solving the structure of an unknown 2
Unit III. 1 H NMR Spectroscopy Basic theory and Instrumentation Know about the NMR phenomenon and basic theory of 1 H and 13 C NMR spectroscopy. Learn the basic components of an NMR spectrometer and know how the spectrum is measured. 1 H NMR-chemical shifts and its measurements in δ scale using TMS as internal standard. Appreciate the fact that shielding and de-shielding by differential electron density around different types of hydrogen/s changes their chemical shifts in a molecule and learn how their chemical shifts can be measured by using TMS as an internal reference. Factors influencing the 1 H NMR chemical shifts Understand the factors influencing the chemical shifts such as electronegativity, inductive effects, resonance effects, Van Der Walls deshielding and anisotropic effects Use of shift correlation charts Learn how the 1 H-NMR correlation charts can be used to understand the approximate chemical shift positions for hydrogen/s in different electronic environments. Integrals in 1 H-NMR spectra Learn how the heights of step curves given with each signal in an NMR spectrum can be used to calculate the number of hydrogen/s associated with that signal Spin-Spin Coupling and multiplicity rules Learn the principle of spin-spin coupling between hydrogens away by two and three bonds (geminal and vicinal coupling) and know how the (n+1) rule is applied to predict the multiplicity and relative heights of constituent lines of each signal. Exchangeable protons Know that hydrogens on nitrogen, oxygen and sulfur are exchangeable. Learn how to identify the exchangeable protons in a spectrum. 3
Solving the structures of simple unknown compounds At this stage, the student shall be able to propose the structures of simple organic compounds from the number, position and multiplicity of the signals in the 1 H-NMR spectrum provided with their molecular formula. Prediction of the expected NMR pattern from structures On the contrary, the student shall be able to predict the expected NMR pattern ie, the number, relative position (δ value) and multiplicity of the signals from the given structure. (students must be able to judge the equivalence of protons in a molecular structure from symmetry considerations). Solvents used in NMR spectroscopy In solution state NMR spectroscopy, the sample is dissolved in an appropriate deuteriated solvent and the knowledge about the choice of the solvent and the position of the residual protons are important Commonly encountered spin systems Study the commonly seen spin systems and learn how to define their multiplicity Splitting diagrams and extraction of chemical shifts and coupling contants. Learn how to draw splitting diagrams for commonly seen spin systems and also learn to extract the chemical shifts and coupling constants. Correlation of coupling constants. Learn how coupling constant data is used to obtain the fine structural details and stereochemistry. Learn how coupling constants are useful in deciding the correct isomers in aromatic compounds. Learn to use H-NMR spectrometry in conjunction with infra red and Mass spectroscopy to determine the exact structure. 4
Unit IV. 13 C-NMR Spectroscopy Pulsed Fourier Transformation techniques in 13 C NMR Coupling and decoupling in 13 C NMR spectra Learn how pulsed FT techniques are useful in obtaining good quality 13 C-NMR spectrum Learn the differences between Broad Band Decoupled (BBD) spectrum and Off-Resonance Decoupled spectrum. DEPT-Spectra and determination of 13 C multiplicity Learn how the multiplicity information is gathered from sub-spectra editing techniques such as DEPT-135 and DEPT-90. 13 C chemical shift range and use of correlation tables Learn how the 13 C-NMR data charts can be used to predict the approximate chemical shift positions for carbons in different environments Application 13 C NMR spectroscopy in structure elucidation Learn how 13 C NMR spectroscopy alone and in combination with other spectroscopic data can be used in structure determination. Unit V. Ultra Violet Spectroscopy Instrumentation in UV spectroscoopy Learn the basic set-up of a UV spectrophotometer HOMO & LUMO Concepts Learn the different types of chromophores that absorb UV radiation and the different types of possible transitions. Quantitative use of UV spectroscopy Learn Beer s law and its application in determining either concentration or molar absorptivity. 5
Interpreting UV spectra Learn how the extent of conjugation in a system and substituents on a system affect the wavelength of absorption Assessment tools include one or more of the following: 1) In class interactive discussions. 2) Quizzes 3) Solving assigned problems from the textbook 4) Comprehensive tests (midterm and final). 6