Spectroscopy II

Electromagnetic radiation, quantization of energy, regions of electromagnetic spectrum, Born –Oppenheimer approximation.

Hooke’s law, vibrational energies of diatomic molecule, determination of force constant, qualitative relation of force constant and bond energies, anharmonicity, vibrational-rotational spectroscopy, P, Q, R branches, breakdown of Born-Oppenheimer approximation, selection rules, Overtones, hotband, combination bands and fermi-resonance.

Different regions of IR spectrum (finger print and functional group region), molecular vibrations, characteristic intensity and position of IR bands of various functional groups (alkanes, alkenes, alkyl halides, alcohols, ethers, carbonyl compounds, primary and secondary amines, carboxylic acids and its derivatives), factors affecting the shift in group frequencies- isotope effect, hydrogen bonding, solvent effect, electronic effects (inductive and mesomeric) and steric effect, different absorption regions in IR spectrum and vibrational coupling.

Energy of atomic orbitals, vector representation of momenta and vector coupling (orbital and spin coupling), term symbols, spectra of hydrogen atom, alkali metal atoms, helium, alkaline earth metals and polyelectronic atoms.

Molecular spectroscopy-energy levels, molecular orbitals- homonuclear and heteronuclear diatomic molecules, vibronic transitions, progression and sequences, derivation of Franck-Condon principle, dissociation and pre-dissociation. Electronic spectra of polyatomic molecules-AH₂ type molecules, formaldehyde and benzene. Emission spectra, radiative and non-radiative decay, internal conversion.

Concept of potential energy curves for bonding and antibonding molecular orbitals, Franck–Condon principle, different electronic transitions and selection rules, Lambert – Beer law, molar absorptivity, effect of solvent on transitions, effect of conjugation, concept of chromophores and auxochromes, bathochromic, hypsochromic, hyperchromic and hypochromic shift. Woodward Fieser rules and its applications on enes, dienes, α,β-unsaturated carbonyls and aromatic compounds.

Jablonski diagram depicting various processes occurring in the excited state, qualitative description of fluorescence, phosphorescence, non-radiative processes (internal conversion, intersystem crossing).

An introduction to fluorescence spectroscopy.

Nuclear properties, pulse technique, Fourier Transform technique and its advantages, quantum number, 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 mercaptans), proton exchange, deuterium exchange, 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, variable temperature dynamic NMR spectroscopy.

Solvent effects, nuclear overhauser effect (NOE), a brief introduction of compounds carrying NMR active nuclei like ¹⁵N, ¹⁹F, ³¹P.

¹³C NMR spectroscopy: Basic principles, chemical shift, (aliphatic, olefinic, alkyne, aromatic, heteroaromatic & carbonyl carbon), proton (1H) coupled ¹³C NMR spectrum, off-resonance and noise decoupled 13C NMR spectrum, DEPT. 2D-NMR spectroscopy– COSY, NOESY, HETCOR.

Mass Spectrometry: Introduction, generation- EI, CI, HRMS, FD and FAB. Mass analyzer-electromagnetic field, quadrupole. Detection of molecular formula (HRMS) and determination 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, nitriles, nitro and halogenated compounds.

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