Infrared Spectroscopy PDF
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Uploaded by IrreplaceableVibraphone1498
Fachhochschule Heidelberg
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Summary
These notes discuss infrared spectroscopy, including diagrams of different molecular structures and how to identify different functional groups using characteristic IR spectra. Examples of identifying different molecules by their functional groups are illustrated
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Chu É PE na in Diff Infrared Spectroscopy Do Now: Draw diagrams to accurately represent the two enantiomers of CHClBr. a at i i i F'd Br Brit FEET KEEF...
Chu É PE na in Diff Infrared Spectroscopy Do Now: Draw diagrams to accurately represent the two enantiomers of CHClBr. a at i i i F'd Br Brit FEET KEEF i Name BP LP BA Diagram Linear 2 O 180 F Be F Trigonglanar 3 O 1200 É F F v Shane bent 2 I 1200 or't o Tetrahedral 4 O 109.50 nigh Trigonalpyradidal 3 I 107 joint n V Shysent 2 2 104.50 in n F Trigonal BiggramiddJ O 9091200 F Egg See Saw 4 I 480 90 Fj 120 F f T Shape 3 2 2180 90 IIF E I Linear 2 3 180 F F Octahedral 6 0 900 get Foyer F.gl F Square 5 I 90 pyramidal F Af Square Planar 4 2 90 F.fi FMQF I i i i d k Bond Vibration Covalent bonds are like springs and can vibrate in different ways when they absorb infrared energy that matches their natural frequencies. Absorption of energy that matches natural frequencies is called resonance. Greenhouse Gases 0 0 E CEO A number of common gases absorb infrared light to a measurable extent in our atmosphere, causing the atmosphere to increase gradually in temperature. Identifying the Functional Groups IR Spectra uses the reciprocal of wavelength, called wavenumber (cm-1). The specific wavenumbers can be used to identify the type of bond present in a molecule. Carboxylic Alcohols Aldehydes Acids Ketones These are all found in section 26 of the data booklet. How could you determine between molecules that have bonds with overlapping wavenumbers. I I 1640 1750 GO Identifying Molecules 3000 3600 On Which of the two spectra is propan-2-ol and which is propanone? propanone 0 11 Lyon The Fingerprint Region The region below 1500cm-1 is known as the fingerprint region, and is unique to every organic molecule. These peaks represent the complex interactions between all of the bonds as they vibrate. Looking at the previous table, which is the only peak within the fingerprint region that you need to be able to identify? OH Peaks tend to be broad Identifying From IR co Peaks tend to be sharp Propan-1-ol beau propanol Propanal C is absorbance at Propanoic Acid Thiggles of the 1700cm I correlates to
