In the group theoretical language developed, a spherical rotor is a molecule that belongs to a cubic or icosahedral point group, a symmetric rotor is a molecule with at least a threefold axis of symmetry, and an asymmetric rotor is a molecule without a threefold (or higher) axis. Linear molecules are linear rotors. Classify each of the following molecules as a spherical, symmetric, linear, or asymmetric rotor and justify your answers with group theoretical arguments: (a) CH4, (b) CH3CN, (c) CO2, (d) CH3OH

In the group theoretical language developed, a spherical rotor is a molecule that belongs to a cubic or icosahedral point group, a symmetric rotor is a molecule with at least a threefold axis of symmetry, and an asymmetric rotor is a molecule without a threefold (or higher) axis. Linear molecules are linear rotors. Classify each of the following molecules as a spherical, symmetric, linear, or asymmetric rotor and justify your answers with group theoretical arguments: (a) CH4, (b) CH3CN, (c) CO2, (d) CH3OH

Physical Chemistry

2nd Edition

ISBN:9781133958437

Author:Ball, David W. (david Warren), BAER, Tomas

Publisher:Ball, David W. (david Warren), BAER, Tomas

Chapter14: Rotational And Vibrational Spectroscopy

Section: Chapter Questions

Problem 14.95E: The mutual exclusion rule states that for certain molecules, vibrations that are IR-active are not...

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The mutual exclusion rule states that for certain molecules, vibrations that are IR-active are not Raman-active, and vice versa. Molecules must have a certain symmetry element in order for the mutual exclusion rule to apply. Examine the character tables in Appendix 3 and determine what that symmetry element is.
In the group theoretical language developed in Focus 10, a spherical rotor is a molecule that belongs to a cubic or icosahedral point group, a symmetric rotor is a molecule with at least a threefold axis of symmetry, and an asymmetric rotor is a molecule without a threefold (or higher) axis. Linear molecules are linear rotors. Classify each of the following molecules as a spherical, symmetric, linear, or asymmetric rotor and justify your answers with group theoretical arguments: (a) CH4, (b) CH3CN, (c) CO2, (d) CH3OH, (e) benzene, (f) pyridine.
Consider the character table given below for the point group D3h, which includes molecules like cyclopropane and BF3. Suppose has been already determined a reducible representation for the collective motions of one such molecule, Γ(3N). What combination of irreps should we remove from it to account for translations & rotations, thereby yielding the purely vibrational representation, Γvib?
Do symmetry elements and operations and the point group of a molecule give information about electronic energy levels within the milecule? Explain.
Indicate the point group of the following ions. Provide molecular structures and indicate the symmetry elements to support your answers. (a) BF2Cl (b) N2O
Identify the point group to which each of the possible isomers of dichloronaphthalene belong.
The structure of [NO3]-is either trigonal planar or trigonal pyramidal draw both possible structures and determine the point group for each. Which irreducible representations represent the translational and rotational modes for each possible structure of [NO3]-? Which irreducible representations correspond to the vibrational modes for each possible structure of [NO3]-? How many degrees of freedom would you expect for each structure of [NO3]-? Calculate T-vibrationaland determine which modes you expect to be IR active for each structure.
The molecule CH2Cl2 belongs to the point group C2v. The displacements of the atoms span 5A1 + 2A2 + 4B1 + 4B2. What are the symmetry species of the normal modes of vibration?
Draw the Lewis structure of the following compounds and identify the point group. Indicate the symmetry operations you performed in determining the point groups.a. 1,8-Dichloronaphthaleneb. Eclipsed dibenzenechromium (Hint: The Cr atom is sandwiched between the two-benzene ring in eclipsed conformation.)c. Borazine (B3H6N3) (Hint: The structure looks like benzene, but instead of C, B and N are the atoms in alternating order.)
a.) Sketch the normal vibrational modes of acetylene and identify the infared inactive ones. b.) Sketch a vibrational energy level diagram below 4000 cm^-1 for acetylene and identify the fundamental transitions. c.) Use group theory to assign acetylene's point group.
Under which conditions (Δ, hϒ) 1,5- and 1,3- sigmatropic shifts takes place and why? Elaborate with the help of orbital analysis.
The chlorophylls that participate in photosynthesis and the haem (heme) groups of cytochromes are derived from the porphine dianion group (8), which belongs to the D4h point group. The ground electronic state is A1g and the lowest-lying excited state is Eu. Is a photon-induced transition allowed from the ground state to the excited state? Explain your answer.