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Organic Chemistry > IR Spectroscopy > Flashcards

IR Spectroscopy Flashcards

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1
Q

What is the IR stretch of a N-H bond?

A

3150-3300 cm-1

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2
Q

What is the IR stretch for a O-H bond?

A

3600-3000 cm-1

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3
Q

What is the IR stretch for C-H bonds?

A

3000 cm-1

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4
Q

What is the IR stretch for triple bonds e.g. C-C or C-N triple bonds?

A

2200 cm-1

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5
Q

What is the IR stretch for double bonds C=O and C=C?

A

C=O 1650-1800 cm-1

C=C 1640 cm-1

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6
Q

What is the IR stretch for aromatic C=C bonds?

A

1500-1600 cm-1

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7
Q

What is the X-H or single bond region!

A

4000-2500 cm-1

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8
Q

What are there two N-H absorptions?

A
  • Because of symmetrical and antisymmetrical vibrations

* antisymmetric vibrations are slightly lower in energy

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9
Q

What effect does increasing s-character have on the C bond strength?

A

An increasing s-character at C increases the bond strength

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10
Q

What is the triple bond region in an IR spectra?

A

2500-2000 cm-1

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11
Q

What is the double bond region?

A

2000-1500 cm-1

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12
Q

What increases the strength of an Alkenes signal?

A

An Alkene signal is stronger if the Alkene is conjugated (polarisation)

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13
Q

What is the carbonyl region?

A

1800-1650 cm-1

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14
Q

What is the key peak of absorbance for a ketone?

A

1710 cm-1

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15
Q

What is the key absorbance for an aldehyde?

A

1730 cm-1

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16
Q

What is the key peak of absorbance for an ester?

A

1740 cm-1

17
Q

How many signals signify an anhydride and what are the wavenumbers of these peaks?

A
  • there are two signals

* 1820 cm-1 and 1750 cm-1

18
Q

What is the key peak that signifies an acyl chloride?

A

1790 cm-1

19
Q

What are the main characteristics of increasing bond strength of C=O?

A

The frequency increased with the electronegativity of the substituents and bond strength increases

20
Q

What is the result of resonance on frequency and bind strength?

A

Frequency decreases with resonance and bond strength also decreases

21
Q

What is the key peak of absorbance for a conjugated ketone e.g. Acetophenone?

A

1685 cm-1

22
Q

What is the key peak absorbance of an enone?

A

1699 cm-1

23
Q

What is the absorbance if a cyclohexanone?

A

1719 cm-1

24
Q

What is the absorbance of a cyclopentanone?

A

1740 cm-1

25
Q

What is the absorbance for 3-membered and 4-membered ketone rings?

A
  • 3-membered ring - 1780 cm-1

* 4-membered ring - 1815 cm-1

26
Q

What is the IR wavenumber for a C-O?

A

1100 cm-1

Organic Chemistry (2 decks)

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