IR Frequencies Flashcards by Bee Who

Q

Stiffer bonds vibrate…

A

faster

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Q

Heaver atoms vibrate…

A

slower

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Q

Hydrogen bonding groups have…

A

broad absorptions

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Q

C-C

A

1200

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Q

C=C, general

A

1660

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Q

C=C, isolated

A

1640-1680

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Q

C=C, conjugated

A

1620-1640

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Q

C=C, aromatic

A

1600

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Q

C(trip)C, terminal

A

2100-2200

sharp; moderate or weak

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Q

C(trip)C, internal

A

very weak or absent

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Q

C-H, sp3

A

2800-3000

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Q

C-H, sp2

A

3000-3100

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Q

C-H, sp

A

3300

sharp

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Q

Alcohol O-H

A

3300

broad

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Q

Amine N-H

A

3300

broad with spikes

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Q

Primary amine/amide N-H

A

3300

broad with 2 spikes

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Q

Secondary amine/amide N-H

A

3300

broad with 1 spike

Q

C-O

A

1000-1200
unreliable if present
indicative if absent
could be only clue for ethers

Q

Ketone C=O

A

1710

intense

Q

Aldehyde C=O

A

1725

intense

Q

Aldehyde C-H

A

2700 and 2800

Q

Acid C=O

A

1710

intense

Q

Acid O-H

A

2500-3500

broad; overlaps C-H region

Q

Ketone

A

C=O at 1710

Q

Aldehyde

A

C=O at 1725

Carbonyl C-H at 2700 and 2800

Q

Acid

A

C=O at 1710

O-H at 2500-3500, broad

Q

Conjugated C=O

A

1685
C=C might not be evident
look for =C-H at 3000-3100

Q

Amide C=O

A

1640-1680

strong and broad

Q

Primary amide C=O

A

1640

strong and broad

Q

Small carboxylic ester C=O

A

1735
characteristic!
lowered by conjugation

Q

C-N

A

1200

rarely useful

Q

C=N

A

1660

intense

Q

C(trip)N

A

2200-2300

strong

Q

N-H, O-H, C-H region

A

2700-3500

Q

C(trip)C and N(trip)N region

A

2100-2300

Q

C=C, C=O, C=N region

A

1600-1850

Q

C-C, C-O, C-N region

A

fingerprint region: 600-1400

Q

Aromatic compound

A

C=C @ 1600

=C-H > 3000

Q

Acid chloride C=O

A

1800

Q

Acid anhydride C=O

A

1750 and 1800

Q

Ring strain…

A

raises frequency

Q

Conjugation…

A

lowers frequency