Sciencemadness Discussion Board

problem with inorganic IR spec

Furboffle - 3-4-2013 at 17:48

In intermediate inorganic lab class we did an experiment where we dissolved triphenylphosphine in acetonitrile, added copper oxide and sulfuric acid, filtered the product which is some form of sulfate salt. we never discussed the product. we ran IR on it to give the attached IR spectra. the purpose was to determine the geometry from the coordination compounds of sulfate and nitrate ions. we were given the ir spectra for silver nitrate and lead nitrate to compare to. the lab manual discusses making a matrix of the vibrational modes to determine the irreducible representations to determine what system of 3N normal modes to use to interpret the number of peaks to look for which will tell the point group symmetry of the nitrate ion to give the geometry: trigonal pyramidal, or trigonal planar geometries.

I don't fully understand how to determine the irreducible representations. Is there anyone that could explain how to go about this.

srhtdb.jpg - 72kB

[Edited on 4-4-2013 by Furboffle]