CHEM 2211 1st Edition Lecture 14 Outline of Last Lecture I II III IV V VI Integrating NMR signals Splitting signal is described by the N 1 rule What causes splitting Coupling constant identifies coupled protons Diastereotopic hydrogens are not equivalent Time dependency of NMRs Outline of Current Lecture I II III Protons bonded to Oxygen and Nitrogen Deuterium in HNMR CNMR Spectroscopy Current Lecture I II III Protons bonded to Oxygen and Nitrogen A Chemical shift of an OH is 2 to 5ppm B Chemical shift increases as hydrogen bonding increases C Protons bonded to alcohols are not split by adjacent protons and show up as singlets on the NMR graph D The signal for OH is generally very broad on the NMR graph Deuterium in HNMR A Deuterium is used in HNMR to determine signals because it doesn t show on HNMR graphs i For example if the HNMR of CH3CH2OCH3 were compared with that of CH3CD2OCH3 then the signal for the second set of hydrogens would be missing CNMR Spectroscopy A Records data on C13 B Requires the use of a FT NMR machine so that multiple scans can be taken and averaged at the same time C Has a range of 0 220ppm and has more easily distinguished signals than HNMR D Number of carbons in molecule is not proportionate to the area under the spikes meaning integration doesn t tell you the number of carbons E No splitting occurs because it is unlikely that the adjacent carbon is a C 13 F All signals are singlets if run as spin decoupling otherwise the attached hydrogens will split the signal
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