Organic and analytical chemistry Essay Example | Topics and Well Written Essays - 500 words

Organic and analytical chemistry - Essay Example IR provides information about the functional groups that are present in the molecules. NMR provides information about the structural relationship of the nuclei in a molecule. Mass Spectrometry: A mass spectrometer measures the deflection of charged particles as they travel across a magnetic field. This depends on their mass and velocity. A small amount of a sample material injected into the device becomes fragmented into various electrically-charged bits of molecules. These ions are then accelerated into the magnetic field section where they travel along a curved trajectory determined by their mass-to-charge ratio, m/e. Adjusting their velocity as they enter this section allows particles of each different mass to strike a detector. The rate at which different particles are detected provides the relative number of pieces of different mass in the molecule. The most important fragment is the M+ fragment, corresponding to the whole molecule. This gives a direct measurement of the molecular weight of the compound. Other fragments can be assigned to certain structural units. But MS cannot provide information about the relative positions of those parts in the m olecule. Infra-red Spectroscopy: IR spectroscopy measures the frequency of infra-red light that is absorbed as it passes through a thin film sample of a compound. The different bonds in a molecule undergo various vibrations and rotations. The frequencies of those motions depends on the masses of the atoms involved and the particular type of motion, and correspond to frequencies in the IR spectrum of light. As IR light is passed through the sample, each bond absorbs energy at its characteristic frequency. The IR spectrograph records the amount of light absorbed at each frequency across the IR spectrum. Some absorbances are characteristic of specific functional groups and appear in very certain ranges of wavelengths. The overall pattern of an