Spectroscopy of Organic Compounds

Introduction, ion-production—EI, CI, FD and FAB, detection of molecular formula – molecular ion, molecular ion peak, nitrogen rule, isotope peak, metastable ions; fragmentation – basic fragmentation types and rules, factors influencing fragmentation, McLafferty rearrangement, fragmentation pattern of hydrocarbons, alcohols, ethers, ketones, aldehydes, carboxylic acids, amines, nitro compounds, alicyclic and heterocyclic compounds. High resolution mass spectrometry.

Self Study: Problems of mass spectral fragmentation of organic compounds for structure determination.

Electronic transitions (185-800nm), Beer- Lambert law, bathochromic and hypsochromic shifts, characterization of organic compounds – application of Woodward-Fieser rule to conjugated dienes, α,β-unsaturated carbonyl compounds, benzene and its substituted derivatives, polycyclic aromatic hydrocarbons, polyenes and polyenynes; steric effects in biphenyls.

Quantitative studies: calculation of force constants, factors effecting the shift in group frequencies – isotope effect, hydrogen bonding, solvent effect, electronic effects (inductive and mesomeric) and steric effect; different absorption regions in IR spectra.

Characteristics functional group absorptions in organic compounds: carbon skeletal vibrations (alkanes, alkenes, alkynes, aromatic compounds), alcohols, phenols, ethers, ketones, aldehydes, carboxylic acids, amides, acid anhydrides, conjugated carbonyl compounds, esters, lactones, amines, amino acids; interpretation of IR spectra of typical  organic compounds.

Self Study: Overtones, combination bands and fermi-resonance.

Introduction, nuclear spin, quantum number and its calculation using nuclear shell model spin pairing rule, chemical shift and factors affecting chemical shift, spin-spin interaction, factors affecting coupling constant, shielding mechanism, chemical shift values and correlation for protons bonded to carbon (aliphatic, olefinic, aldehydic and aromatic) and other nuclei (alcohols, phenols, enols, carboxylic acids, amines, amides and mercaptides), chemical exchange, effect of deuteration, complex spin-spin interaction between two, three, four, and five nuclei (first order spectra), hindered rotation, Karplus curve variation of coupling constant with dihedral angle, simplification of complex spectra – nuclear magnetic double resonance, contact shift reagents, dynamic NMR spectroscopy.

Solvent effects, Fourier transform technique and its advantages, nuclear overhauser effect (NOE), a brief idea of compounds carrying NMR active nuclei like N¹⁵, F¹⁹, P³¹.

¹³C NMR spectroscopy: general considerations, chemical shift, (aliphatic, olefinic, alkyne, aromatic, heteroaromatic & carbonyl carbon), proton (¹H) coupled ¹³C NMR spectrum, off-resonance and noise decoupled ¹³C NMR spectrum, 2DNMR spectroscopy – Cosy, Noisy spectroscopy.

Structure elucidation of simple organic compounds by joint application of IR, UV, NMR and mass spectroscopy.