Spectrum 1: Tetralin (R4, C2)

Frequency Assignment
3000-3101 n(CH, sp2)
2839-2928 n(CH, sp3)
1494, 1602 n(C=C, aromatic)
1453

d(CH2, bend)
742 oop, ortho subst.

Spectrum 2: Phenyl acetaldehyde (R2, C2)

Frequency Assignment
3427 C=O-overtone
3030-3088 n(CH, sp2)
2920 n(CH, sp3)
2728, 2826 n(CHO, aldehyde)
1724 n(C=O, aldehyde, sat.)
1498, 1602 n(C=C, aromatic)
1454 d(CH2, bend)
701, 751 oop, mono subst.

Spectrum 3: m-Anisic acid (R3, C1)

Frequency Assignment
2500-3500 n(OH, carboxylic acid)
1694 n(C=O, acid, conj.)
1490, 1606 n(C=C, aromatic)
1292 n(C-O, acid)
1044 n(C-O, ether)
755 oop, meta subst.

Spectrum 4: Propyl proprionate (R2, C4)

Frequency Assignment
3462 C=O-overtone
2883-2983 n(CH, sp3)
1741 n(C=O, ester)
1380, 1464 d(CH2, CH3, bend)
1084, 1190 n(C-O-C, ester)

Spectrum 5: o-Toluidine (R4, C1)

Frequency Assignment
3382 n(NH, sec. amine)
3023-3052 n(CH, sp2)
2845-2973 n(CH, sp3)
1489, 1587 n(C=C, aromatic)
1449 d(CH2, bend)
749 oop, mono subst.

Spectrum 6: Citraconic anhydride (R3, C3)

Frequency Assignment
3594 C=O-overtone
3117 n(CH, sp2)
2931-2966 n(CH, sp3)
1769, 1845

n(C=O, anhydride)
1651 n(C=C, alkene)
979, 1237 n(C-O-C, anhydride)

Spectrum 7: a-methylbenzyl alcohol (R1, C3)

Frequency Assignment
3350 n(OH, alcohol)
3030-3107 n(CH, sp2)
2878-2973 n(CH, sp3)
1493, 1601 n(C=C, alkene)
1369, 1453 d(CH3, bend)
1078 n(C-O, alcohol)
699, 761 oop, mono subst.

Spectrum 8: 1-Chloro-2-pentene (R4, C3)

Frequency Assignment
2847-2981 n(CH, sp3)
2241 n(C=C, alkyne)
1378, 1455 d(CH2, CH3, bend)
692 n(C-Cl)

Spectrum 9: Crotonaminde (R3, C4)

Frequency Assignment
3149, 3326 n(NH2, amide)
2916-2966 n(CH, sp3)
1681 d(C=O, amide)
1613 n(C=C, alkene)
1373, 1447 d(CH3, bend)
974 oop, trans alkene

Spectrum 10: Biphenyl (R4, C4)

Frequency Assignment
3035-3111 n(CH, sp2)
1481, 1599 n(C=C, aromatic)
700, 730 oop, mono subst.


Note: The designation behind the name is the row and column number the molecule is located in the table.

General comments:

1. The average grade for the assignment is 36.6 points (out of 40). If you scored around or less than 30 points, I would advise you to see your TA or the instructor to seek some help.

2. One of the most common mistakes was not to analyze the n(C-H) region correctly to determine what type of compound (alkane, alkene, aromatic, or mixed) is present. Just writing "sp3" or "C-H" is not sufficient here.

3. The n(OH) peaks for carboxylic acids and alcohols look very different and can be easily identified by looking at them (see reader). However, in some cases intramolecular hydrogen bonding broadens and shifts (to lower wavenumbers) the peak of an alcohol.

4. Carbonyl peaks can be shifted to lower wavenumbers when the carbonyl function is conjugated to another p-system e.g. double bond or aromatic ring.

5. Nitro groups show two intense peaks in the IR spectrum: one between 1300-1400 cm-1 for the symmetric stretching mode, the other one between 1500-1600 cm-1 for the asymmetric stretching mode.

6. The presence of two peaks in the carbonyl range (1630-1850 cm-1) indicates either the presence of an "anhydride type" of function or two different carbonyl functions.

7. Peaks due to amine, alkyne or alcohol functions are very different in appearance. Alkyne peaks (CH stretch) are very sharp and fairly intense due to an "isolated" motion. Amine peaks are usually a little broader and less intense. The presence of two peaks suggests a primary amine (NH2) while secondary amines show only one peak in this range. Alcohols (OH-stretch) usually show a rounded peak in this area.

8. If the spectrum shows a lot of peaks (independent from their size), the molecule has to have a lot of atoms and also cannot be very symmetric.