CHEM 205 Lecture Notes - Electric Dipole Moment, Wavenumber, Spectroscopy
Document Summary
Infrared spectroscopy: relies on energy of molecular vibrations (high energy, frequency of radiation about 10^14hz, making them 1000000x more energetic than. Nmr spin transitions: unit used=wavenumber (in 1/cm)=1/lambda, gives info about molecular structure, inter and intramolecular interactions, chemical composition, oscillation of molecule (diatomics)=harmonic oscillation where wavenumber=see. The difference in energy between the resonance levels give rise to the photon energies required: potential energy=v(x)=. 5kx^2 where x is bond length. Speed of light should be given in cm/s. k is in n/m: selection rules, 1. Electric dipole moment of molecule must change during vibration: must be polar. Ir shown as transmittance not absorbance, thus the dips=peaks! Usually when looking, just disregard wavenumbres under 1400: almost always there is a peak near 3000 due to c-h stretch, peaks between 2800-2000 indicate triple bond, peaks between 1900 and 1700 indicate c=o. Top ir shows that there is 1 c=o bond due to peak at 1700.
