CHEM 2211 1st Edition Lecture 14 Outline of Last LectureI. Integrating NMR signalsII. Splitting signal is described by the N+1 ruleIII. What causes splitting?IV. Coupling constant identifies coupled protonsV. Diastereotopic hydrogens are not equivalentVI. Time dependency of NMRsOutline of Current LectureI. Protons bonded to Oxygen and NitrogenII. Deuterium in HNMRIII. CNMR SpectroscopyCurrent LectureI. Protons bonded to Oxygen and NitrogenA. Chemical shift of an –OH is 2 to 5ppmB. Chemical shift increases as hydrogen bonding increasesC. Protons bonded to alcohols are not split by adjacent protons and show up as singlets on the NMR graphD. The signal for –OH is generally very broad on the NMR graphII. Deuterium in HNMR A. Deuterium is used in HNMR to determine signals because it doesn’t show on HNMR graphsi. For example, if the HNMR of CH3CH2OCH3 were compared with that of CH3CD2OCH3, then the signal for the second set of hydrogens would be missingIII. CNMR SpectroscopyA. Records data on C13B. Requires the use of a FT-NMR machine so that multiple scans can be taken and averaged at the same timeC. Has a range of 0-220ppm and has more easily distinguished signals than HNMRD. Number of carbons in molecule is not proportionate to the area under the spikes meaning integration doesn’t tell you the number of carbonsE. No splitting occurs because it is unlikely that the adjacent carbon is a C13F. All signals are singlets if run as spin decoupling, otherwise the attached hydrogens will split the
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