Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.
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Transcript of Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.
Introduction to Spectroscopy
Illustrations from R. T. Morrison and R. N. Boyd,
Organic Chemistry
NMR Chemical Shift
• Chemical Shift ~ measure of local electron density• =( - ref )/ref * 106 ppm
Peak Integrals
• 3.8 : 2.9 : 8.8 = 1.31 : 1 : 3.03 = 3.9 : 3 : 9• If formula is known C11H16 :
• 16 H/15.5 units = 1.03 H per unit
Correlation Charts
13C
Spin-Spin Splitting
• Multiplicity : singlet, doublet, triplet, quartet, pentet• Determined by number of near neighbors• N-Equivalent neighbors: multiplicity = N + 1
• Branched Chains have Characteristic Patterns• Quartet-triplet = ethyl• Septet-doublet = gem-dimethyl • (geminal – attached to same atom)
Inequivalent Neighbors
• N-Neighbors: multiplicity = 2N
Spin Systems
• Mutually coupled (or isolated equivalent spins)• Two spin systems
Unknown
• Double bonds and rings: CcHhOoNn
• Dbr = (2c-h+n+2)/2 (2*8-10+2)/2 = 4
Effect of Field Strength
• Chemical Shift the same in ppm• Multiplets have same spacing in Hz• 60 MHz: 10 ppm = 600 Hz 1 Hz = 0.0166 ppm• 500 MHz: 10 ppm = 5000 Hz 1 Hz = 0.002 ppm
500 MHz
• Multiplets simplified (more first order)– Better definition in aromatic region
• More sensitive (less sample or less time)
Infrared Spectroscopy
• Molecular Vibrations• Characteristic of functional groups• Chain Branching
%T
Aldehydes and Ketones
• Aldehyde RCHO 1725 cm-1 Ketone R2CO 1710 cm-1 Cyclobutanones 1780 cm-1
• Aromatic ArCHO 1700 cm-1 Aromatic ArCOR 1690 cm-1 Cyclopentanones 1740 cm-1
• Conjugated• -C=C-CHO 1685 cm-1 -C=C-C=O 1675 cm-1 • | | |
Alcohols
Carboxylic Acids
• Aliphatic R-COOH 1700-1725 cm-1 Conjugated -C=C-COOH 1680-1700 cm-1
• Aromatic Ar-COOH 1680-1700 cm-1
Carboxylic Acid Derivatives
• Esters R-COOR C=O 1714-1740 cm-1
• two bands C-O-R 1050-1300 cm-1
Ethers
Phenols
• -CH2-CH2-CH2-CH2- rock 720 cm -1