CHEM 222 Lecture Notes - Absorption Band, Aliphatic Compound, Tripe

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18 Apr 2012
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CHEM 222 1/12/2012 6:56:00 AM
- IR tutor
Spectral interpretation always starts at the high end because higher
frequencies are easier to interpret
1-HEXENE
o Can you determine which peaks arise from the double bond?
(Hint: overlay the spectrum of hexane)
o Absorption peak around 3000, sp3 bonds C-H bond
1-HEPTYNE
o sp bonds, well above 3000
o CH stretch: very sharp, thin shape of absorption band
o ONLY triple bonds (C-C, C-N) around 2200
HEPTYL CYANIDE
o C-N tripe bond, aliphatic
o Nothing above 3000
o Characteristic peak around 2200, C-N triple bond
TOLUENE (methylbenzene)
o Sp3 stretch band shorter than sp2, rare case
o Combination/overtone bands observed at lower frequencies
o Characteristic of aromatics: few sharp strong peaks around
700
HEXANOL
o Aliphatic compound with terminal alcohol
o Very smooth peak, relatively strong and broad **SHAPE
MATTERS = Typical O-H bond of alcohol
o Absorption band around 3300-3400
o Stretches: sp3 hybridized carbons, C-H stretches slightly
below 3000
o Band visible around 1100-1200, strong sharp band C-O bond
(carboxylic acid, alcohols, ethers)
o *Whether you have 1, 2 or 3 OH groups, you’ll only get ONE
band
HEXYL AMINE
o Absorption around 3300-3400, weak and triangular peaks
o *NH2, two bands; NH, one band
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When you get two bands, means NH is on the same
carbon (double check)
o C-O single bond appears around 1100
Carbonyl containing compounds
HEPTALDEHYDE
o Aliphatic compound, sp3 stretches
o Highly characteristic of aldehyde CH bond, weak peak at
2700-3000
o Carbonyl compound absorption around 1700
3-HEPTANONE
o C=O stretch, strong absorption around 1700
o *Difference between ketone and aldehyde: ketone DOESN’T
have CH weak peak
HEPTANOIC ACID
o Can you determine which peaks arise from the acid group?
Overtone region: characteristic of COOH group, range
2500-300
o Region below 1400: fingerprint region
ETHYL ACETATE
o Can you determine which peaks arise from the ester group?
Carbonyl bond at 1740 (a little high for
aldehydes/ketones usually around 1700-1710)
Above 1200, broad for C-O-O
BUTYRIC ANHYDRIDE
o Can you determine which peaks arise from the anhydride?
(Carbonyl-oxygen-carbonyl)
Two peaks: one around 1700, one around 1800
NMR
- MS gives you formula
- IR gives you functional groups
- NMR gives you so much more….
***NO THEORY ON EXAM!****
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- Proton (H) NMR and carbon 13 is most common type of NMR
PROTON NMR
1. Number of signals = number of chemically different protons
2. Chemical shifts (delta) = type of different environments around protons
(more/less shielding)
3. Integration = ratio of different types of protons
4. Signal splitting = number of adjacent protons
5. Signal shape = hydrogen bonding
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