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

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

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

Page 1: 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

Page 2: 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

Page 3: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

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

Page 4: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.
Page 5: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

Correlation Charts

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Page 7: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

13C

Page 8: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

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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Page 10: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

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

Page 11: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

Inequivalent Neighbors

• N-Neighbors: multiplicity = 2N

Page 12: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

Spin Systems

• Mutually coupled (or isolated equivalent spins)• Two spin systems

Page 13: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

Unknown

• Double bonds and rings: CcHhOoNn

• Dbr = (2c-h+n+2)/2 (2*8-10+2)/2 = 4

Page 14: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

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

Page 15: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

500 MHz

• Multiplets simplified (more first order)– Better definition in aromatic region

• More sensitive (less sample or less time)

Page 16: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

Infrared Spectroscopy

• Molecular Vibrations• Characteristic of functional groups• Chain Branching

%T

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Page 18: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

Aldehydes and Ketones

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• 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 • | | |

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Alcohols

Page 21: Introduction to Spectroscopy Illustrations from R. T. Morrison and R. N. Boyd, Organic Chemistry.

Carboxylic Acids

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• Aliphatic R-COOH 1700-1725 cm-1 Conjugated -C=C-COOH 1680-1700 cm-1

• Aromatic Ar-COOH 1680-1700 cm-1

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Carboxylic Acid Derivatives

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• Esters R-COOR C=O 1714-1740 cm-1

• two bands C-O-R 1050-1300 cm-1

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Ethers

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Phenols

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• -CH2-CH2-CH2-CH2- rock 720 cm -1