Organic Chemistry: Spectroscopy – Flashcards
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infrared spectroscopy
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measures molecular vibrations of characteristic functional groups
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alkanes IR C?H wavenumber
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2800-3000 cm?¹
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alkanes IR C?C wavenumber
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1200 cm?¹
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alkenes IR =C?H wavenumber
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3080-3140 cm?¹
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alkenes IR C=C wavenumber
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1645 cm?¹
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alkynes IR C?C wavenumber
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2200 cm?¹
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alkynes IR ?C?H wavenumber
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3300 cm?¹
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aromatic IR C?H wavenumber
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2900-3100 cm?¹
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aromatic IR C?C wavenumber
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1475-1625 cm?¹
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alcohols IR O?H wavenumber
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3100-3500 cm?¹ broad
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ethers IR C?O wavenumber
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1050-1150 cm?¹
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aldehydes IR (O)C?H wavenumber
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2700-2900 cm?¹
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aldehydes IR C=O wavenumber
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1700-1750 cm?¹
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ketones IR C=O wavenumber
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1700-1750 cm?¹
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carboxylic acids IR C=O wavenumber
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1700-1750 cm?¹
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carboxylic acids IR O?H wavenumber
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2800-3200 cm?¹ broad
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amine IR N?H wavenumber
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3100-3500 cm?¹ sharp
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UV spectroscopy
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involves passing ultraviolet light through a chemical sample and plotting absorbance vs. wavelength most useful for studying compounds containing double bonds and heteroatoms with lone pairs
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¹H-NMR
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a form of nuclear magnetic resonance
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chemical shifts (?) are
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downfield from TMS
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RCH? chemical shift
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0.9 ppm
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RCH? chemical shift
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1.25 ppm
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R?CH chemical shift
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1.5 ppm
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?CH=CH chemical shift
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4.6-6 ppm
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?C?CH chemical shift
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2-3 ppm
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Ar-H chemical shift
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6-8.5 ppm
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?CHX chemical shift
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2-4.5 ppm
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?CHOH/?CHOR chemical shift
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3.4-4 ppm
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RCHO chemical shift
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9-10 ppm
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RCHCO? chemical shift
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2-2.5 ppm
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?CHCOOH/?CHCOOR chemical shift
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2-2.6 ppm
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?CHOH?CH?OH chemical shift
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1-5.5
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ArOH chemical shift
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4-12
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?COOH chemical shift
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10.5-12
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?NH? chemical shift
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1-5
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when analyzing an NMR spectrum, look for
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1. types of protons 2. position of peaks 3. integration of peaks 4. splitting
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types of protons
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correspond to the number of peaks seen in the spectrum
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position of peaks
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the further left-shifted (downfield) the peak, the more deshielded the proton usually this corresponds to more electron-withdrawing groups
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integration of peaks
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the larger the integration, the more protons contained under the peak
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splitting
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hydrogens on adjacent carbons will split a peak into n + 1 subpeaks, where n is the number of hydrogens on the adjacent carbon
