Question

Use Web Mo for (pyrazine (C4H4N2))    Point group is D2h

(a) Identify and clearly sketch by hand the symmetry elements of the molecule. (b) Calculate the number of degrees of freedom and number of vibrations for the molecule. (c) Determine how the degrees of freedom of the molecule are distributed amongst the irreducible representations of the point group show clearly all your working. (d) Subtract the translations and rotations and hence determine how the normal vibrations of the molecule are distributed amongst the irreducible representations - show clearly all your working. (e) For each vibration, using the Transition Moment Integral, state whether the fundamental transition is allowed or forbidden in the IR and Raman spectra based on symmetry arguments. Explain this clearly. () What is the symmetry species of the direct product B1gAB1u in D2h? Would a vibrational transition from a B1g to a B1u state be allowed in the (i) IR and (ii) Raman spectrum? (g) Record the Z- matrix in your report along with a labelled diagram of the molecule that includes the atom numbers, bond lengths and angles from your Z-matrix. (h) Use WebMO to animate each of the vibrations. Sketch any 5 of these modes; label each of your sketches with the symmetry (e.g., A1, B2g), a written description of the motion (e.g., symmetric stretch, out-of-plane) and the calculated frequency in wavenumbers. () Record the intensity calculated for each fundamental transition for both IR and Raman (Appears in the raw output file, see the example below). Then print out (or sketch) the predicted IR spectrum and predicted Raman spectrum (on the same plot if you wish) Label the peaks with the calculated frequency and the corresponding symmetry. Can you see the correct number of predicted fundamental vibrations? If not, why not? Find in the literature/reference an IR spectrum or Raman of your molecule. Include the details of the reference. Does the reported spectrum compare well to your predictions? Discuss why/why not.

Answer 1

Plame Cortra Scanned with CS CamScanner

6) lpon ral analysi re that 10 alems we 1oll ee all willhaue 3. Jadamulon degae radona ebch ach gu 3conseclue alos athe bill a rotalo dlagso Tho entre Rolale abot heCentra cam dgnal gep Ond the eit the Total DOF 3KJO 1x6 DOf- 38 By using thMobus Inuern caleulat 0ucilole Bne the di The ns dapich he