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Published byChristiana Ray Modified over 9 years ago
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Analytical chemistry 2 Mass spec cont. IR absorption spec
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Mass spec starter 1.What are the 4 main stages of mass spec? 1.Ionisation 2.Acceleration 3.Deflection 4.Detection
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Mass spec for ethanol - interpret 1. M+2. Base peak 3. 4. 5.
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Infrared Spectroscopy Visible light is made up of a continuous range of different electromagnetic frequencies.....so is Infrared radiation (the eye just can’t see it) Each frequency of light (including infra-red) has a certain energy.
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How IR spectroscopy works… Shine a range of IR frequencies, one at a time through a sample of organic compound and at some of the frequencies the energy will be absorbed. A detector on the other side of the sample would show that some frequencies are absorbed whilst others are not.
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If a particular frequency is being absorbed as it passes through the compound being investigated, it must mean that its energy is being transferred to the compound. Energies in infra-red radiation correspond to the energies involved in bond vibrations.
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Bend and Stretch In covalent bonds, atoms aren't joined by rigid links; the two atoms are held together because both nuclei are attracted to the same pair of electrons. The two nuclei can vibrate backwards and forwards - towards and away from each other - around an average position.
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All molecules absorb infrared radiation; absorbing energy makes the bonds vibrate. Every bond vibrates at its own frequency, dependant upon bond strength, bond length and the mass of atoms involved in bond. STRETCHING BENDING
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Fingerprint regions You must be able to identify the following peaks. – C-H in alkanes/alkenes/aldehydes – O-H in alcohols/carboxylic acids – N-H in amines – C=O in aldehydes and ketones – C-X in halogenoalkanes
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Which functional groups are present in this spectrum?
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