Molecular formulas gaining structural information from

HOW TO Gain Structural Information from Molecular Formulas and the Index of Hydrogen Deficiency 182... 

HOWTO GAIN STRUCTURAL INFORMATION FROM MOLECULAR FORMULAS AND THE INDEX OF HYDROGEN DEFICIENCY... 

Mass Spectrometry If a mass spectrometer is available, a mass spectrum will probably have been run at an early stage to determine the exact molecular weight and the molecular formula as described above. An attempt may also be made to gain further structural information from the cracking pattern in the spectrum (Fig. 3-1). Since the energy available when... 

In problems you will be given the molecular formula of a compound and asked to deduce its structure from its spectroscopic properties sometimes from its infrared or nmr spectrum alone, sometimes from both. The compound will generally be a simple one, and you may need to look only at a few features of the spectra to find the answer. To confirm your answer, however, and to gain experience, sec how much information you can get from the spectra try to identify as many infrared bands as you can, to assign all nmr signals to specific protons, and to analyze the various spin-spin splittings. Above all, look at as many spectra as you can find in the laboratory, in other books, in catalogs of spectra in the library. 

All modem MS instmments have dedicated computer systems for control of the spectrometer, collection of the data, and analysis. The mass plots are normalized to a common gain factor and the electronic baseline is subtracted. From the measurement of the absolute mass of an oligomer or a polymer fragment ion, the most probable elemental composition can be computed by the mass spectrometer data station. The more accurate the mass measurement, the greater are the restrictions on the chemical formulas that can be computed. Generally, this elemental composition information is all that is needed to confirm a suspected molecular structure. 

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