Mass spectrometry infrared region

Laser Desorption Ionization. A pulsed laser beam can be used to ionize samples for mass spectrometry. Because this method of ionization is pulsed, it must be used with either a time of flight or a Fourier transform mass spectrometer (Section 1.4.5). Two types of lasers have found widespread use A COz laser, which emits radiation in the far infrared region, and a frequency-quadrupled neodymium/yttriumaluminum-garnet (Nd/YAG) laser, which emits radiation in the UV region at 266 nm. Without matrix assistance, the method is limited to low molecular weight molecules (<2 kDa). 

The Infrared Region 515 12-4 Molecular Vibrations 516 12-5 IR-Active and IR-lnactive Vibrations 518 12-6 Measurement of the IR Spectrum 519 12-7 Infrared Spectroscopy of Hydrocarbons 522 12-8 Characteristic Absorptions of Alcohols and Amines 527 12-9 Characteristic Absorptions of Carbonyl Compounds 528 12-10 Characteristic Absorptions of C—N Bonds 533 12-11 Simplified Summary of IR Stretching Frequencies 535 12-12 Reading and Interpreting IR Spectra (Solved Problems) 537 12-13 Introduction to Mass Spectrometry 541 12-14 Determination of the Molecular Formula by Mass Spectrometry 545... 

The compounds Fe(CO), g(CNC4H3Me2-l,3X, (n = 1-5) are characterized by IR vibrational spectroscopy (vco and Vnc> 1800-2200-on region) and by NM R spectroscopy (aromatic and methyl protons). Selected spectroscopic data for these complexes are given in the Table I. Infrared spectroscopy may conveniently be used for the monitoring of the progress of the substitution reaction, and NMR spectroscopy for an estimate of product purity. The complexes may also be characterized by mass spectrometry... 

Esters are carboxylic acid derivatives, and the spectrum of ethyl acetate is shown in Figure 14.19D. The carbonyl absorption does not distinguish this compound from an aldehyde or a ketone, but there is the C-O absorption at about 1200 cm 1. Because this is in the fingerprint region, however, its position can be difficult to identify. This is clearly the case for methyl pentanoate, where the C-0 absorption can easily be missed or misidentified. Based only on the infrared, it may be difficult to distinguish an ester from an aliphatic aldehyde or ketone. If the formula is known, however (from mass spectrometry), the identification is easier because an ester has two oxygen atoms, whereas the aldehyde or ketone has only one. 

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