CHE 202 Edition 1nd Lecture 2 Outline of Last Lecture I Overview of Spectroscopy II Review of Waves III Electromagnetic Spectrum Waves a Infared Region b Molecular Vibrations Outline of Current Lecture I Spectroscopy of Hydrocarbons a Bond Stretching II Carbon Saturation a Index of Hydrogen Deficiency III Conjugation a Hybridization b Carbonyl Compounds Current Lecture Spectroscopy of Hydrocarbons Bond Stretching o OH and NH bonds Occur around 3300cm 1 OH alcohols are broad and rounded Primary and secondary NH amines are broad and sharp Tertiary OH NH do not show a signal Carbon Saturation Index of Hydrogen Deficiency IHD These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Degree of unsaturation method for finding the exact number of hydrogens in a molecule ex H3C CH3 is missing two hydrogens due to the C C bond Shows the number of multiple bonds and irregularities Equation Numbers of C Carbon H Hydrogen X Halide N Nitrogen o 2 2C H X N 2 IHD of 4 or greater shows an aromatic ring Ketones Aldehydes and acids o Carbon Oxygen C O double bond is found around 1710cm 1 o Carboxylic Acid C O O is broad and mixed in with C H stretches Conjugation Hybridization o Conjugation lowers frequency through pi bond overlapping o With increasing S character wave number increases Sp3 Sp2 Sp Conjugation of Carbonyl Compounds o Resonance lowers the wave number when the electron cloud is less dense o Amides appear around 1640 1680cm 1 with carbonyl groups 3300cm 1 when with a N H bond o Esters appear around 1735cm 1 Cyclic strained ketones have an increased frequency