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Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

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Presentation on theme: "Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry."— Presentation transcript:

1 Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry

2 NMR Chemical Shift Chemical Shift ~ measure of local electron density  =  ( - ref )/ ref * 10 6 ppm

3 Peak Integrals 3.8 : 2.9 : 8.8 = 1.31 : 1 : 3.03 = 3.9 : 3 : 9 If formula is known C 11 H 16 : 16 H/15.5 units = 1.03 H per unit

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5 Correlation Charts

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7 13 C

8 Spin-Spin Splitting Multiplicity : singlet, doublet, triplet, quartet, pentet Determined by number of near neighbors N-Equivalent neighbors: multiplicity = N + 1

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10 Branched Chains have Characteristic Patterns Quartet-triplet = ethyl Septet-doublet = gem-dimethyl (geminal – attached to same atom)

11 Inequivalent Neighbors N-Neighbors: multiplicity = 2 N

12 Spin Systems Mutually coupled (or isolated equivalent spins) Two spin systems

13 Unknown Double bonds and rings: C c H h O o N n Dbr = (2c-h+n+2)/2 (2*8-10+2)/2 = 4

14 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

15 500 MHz Multiplets simplified (more first order) – Better definition in aromatic region More sensitive (less sample or less time)

16 Infrared Spectroscopy Molecular Vibrations Characteristic of functional groups Chain Branching %T

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18 Aldehydes and Ketones

19 Aldehyde RCHO 1725 cm -1 Ketone R 2 CO 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 | | |

20 Alcohols

21 Carboxylic Acids

22 Aliphatic R-COOH 1700-1725 cm -1 Conjugated -C=C-COOH 1680-1700 cm -1 Aromatic Ar-COOH 1680-1700 cm -1

23 Carboxylic Acid Derivatives

24 Esters R-COOR C=O 1714-1740 cm -1 two bands C-O-R 1050-1300 cm -1

25 Ethers

26 Phenols

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28 -CH2-CH2-CH2-CH2- rock 720 cm -1


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