instrumental methods of Structure determination I Nuclear Magnetic Resonance (NMR) -Info about structure. 2 Infrared Spectroscopy (IR)- Triggering molecular vibrations through irradiation with Infrared light. Provides mostly information about the presence / absence of certain functional groups 3 Mass Spectrometry- - Info about molecular mass. 4. Ultraviolet Spectroscopy (UV)- - In to about the bonds Spectrosopy- Study of Spectral Information physical Molecule response Stimulus Detecting Instrument Visual (most common) representation, or Spectrum Upon irradiation with infrared light, certain bonds respond by vibrating faster This response can be detected and translated into a visual representation called a Spectrum Transmission vs. Absorption When a chemical sample is exposed to the action of IR light, it can absorb some frequences and transmit the rest Some of the light can also be reflected back to the source.
IR chemical Transmitted Detector Source Sample light From all the frequence it receive the chemical Sample can absorb (retain) specific frequencies and allow the rest to pass through it (transmitted light). The detector detects the transmitted frequencies, and by doing Q so also reveals the values of the absorbed frequencies Infrared radiation is largely thermal energy. It induces stronger molecular vibrations in covalent bonds, which can be viewed as springs holding together two masses, or atoms. Specific bonds respond to (absorb) Specific frequence amor equilibrium Stretched bond length Compressed