GC-MS, IR,NMR - IR 1H-NMR 13C-NMR and Mass Spectroscopy 11...

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IR, 1 H-NMR, 13 C-NMR and Mass Spectroscopy 11 March 2008 Introduction A mass spectroscopy test is used to determine the structure of a compound and its name by determining which functional groups are present. Mass spectroscopy also allows us to determine the molecular weight of the compound and its fragments. This is the major goal of this part of the experiment. The sample being tested is injected in the injection port where the volatile molecules are vaporized and are carried by helium gas, which is the mobile phase, to the column, which is the stationary phase. The column provides a means for separating the components of the mixture based on intermolecular forces of attraction. The compound passes though an ion chamber where in is bombarded by high energy electrons. The data sheet provided shows multiple peaks. Usually, there is a peak that corresponds to the original molecular weight of the compound plus 1 g/mol, referred to as an M + . With the separation of each fragment, the molecular weight shows up at a peak corresponding to the molecular weight of the new compound. Also, if there is a peak at 77ppm, the compound is aromatic, due to the molecular weight. Infrared spectroscopy is another method of testing to determine the functional groups of an unknown compound. The frequency of the light absorbed is given in units of wave numbers, cm - . When an organic compound absorbs IR light, the energy is low and no bonds are broken. Vibrations of the compound are quantized and only specific frequencies will induce these vibrations. Certain functional groups are signaled by specific peaks on IR spectrums. On the data sheet of an IR spectroscopy, the peaks are pointing down. As previously
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This note was uploaded on 07/15/2008 for the course CH 221 taught by Professor Tilley during the Spring '08 term at Stonehill.

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GC-MS, IR,NMR - IR 1H-NMR 13C-NMR and Mass Spectroscopy 11...

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