Details of CH4102 (Autumn 2020)

Level: 4 Type: Theory Credits: 4.0

Course CodeCourse NameInstructor(s)
CH4102 Molecular Structure and Symmetry Debasis Koley

A: Bonding in organic and inorganic chemistry
Construction of qualitative MO diagram using the concepts of SALC and Projection operator in followings:
(i) SALC and MO diagram in homo- and hetero-nuclear diatomic molecules (H2, N2, O2, CO, NO )
(ii) SALC and MO diagram in AHn (A=second-row atom) (BeH2, BH3, CH4, NH3, H2O, HF), pendant atom
(iii) SALC and MO diagram in Mxn, e.g., alpha-bonding in BF3, XeF4, BrF5, pi-bonding in CO2, SF6
(iv) SALC and MO diagram in pi-electronic systems. pi-approximation (carbonate ion, trans-butadiene, cyclobutadiene, etc.), pi-MOs of carbocyclic systems (e.g., benzene, naphthalene); Hckel MO theory.

B: Bonding in transition-metal complexes
Transformation properties of Atomic orbitals. Frontier orbitals.
(i) LCAO-MO for alpha-bonding in Oh, Td, D4h and other geometries.
(ii) LCAO-MO for pi-bonding in Oh, Td, D4h and other geometries.
(iii) LCAO-MO in cage and cluster compounds (B6H62, metal carbonyl)
(iv) LCAO-MO in sandwich complexes (ferrocene, dibenzenechromium)

C: Molecular vibration
Symmetry species of normal vibrations ( ) in polyatomic molecules in various geometries.
Selection rules in IR and Raman spectroscopy, Polarization, Overtones, combination bands and Hot bands , Stretching and bending mode analysis, Fermi resonance, Rule of mutual exclusion. Using correlation tables with vibrational spectra (CH4 and CH3D).
Examples: (H2O, CO2, XeF4, BCl3, NH3, B2H6, C2H4, CH4, SF6, C6H6, etc.)

D: Electronic Spectroscopy
Molecular term symbols (B2, N2, O2, etc)
Electric dipole transition. Orbital and spin selection rule. Frank-Condon factor, Vibronic selection rule, Relaxation in selection rule. Magnetic dipole selection rules, single-photon and two-photon spectroscopy, forbidden transition, Laporte selection rule
Ligand field theory of transition-metal complexes: electronic structure of free atoms and ions, Splitting of levels and terms in various chemical environment (Oh, Td), weak fields and strong fields, correlation table, Jahn-Teller effect, Orgel diagram, correlation diagram, method of descending symmetry, non-crossing rule. Hole formalism, Tanabe-Sugano diagram, Charge-transfer spectra.

E: Photochemistry and conservation of orbital symmetry
Woodward Hoffmann rule, Frontier orbitals, Symmetry State Correlation, Electrocyclic reaction, Cycloaddition reaction (ethylene dimerization), Sigmatropic rearrangement


Course Credit Options

Sl. No.ProgrammeSemester NoCourse Choice
1 IP 1 Not Allowed
2 IP 3 Elective
3 IP 5 Not Allowed
4 MR 1 Not Allowed
5 MR 3 Not Allowed
6 MS 5 Not Allowed
7 MS 7 Core
8 MS 9 Not Allowed
9 RS 1 Elective
10 RS 2 Elective