Paraffins (Aliphatic Alkanes)

PARAFFINS (ALIPHATIC ALKANES)

The paraffins are saturated hydrocarbons and thus contain only C-C and C-H single bonds.
IR radiation induces stretching and bending vibrations of these units.

The C-C bending occurs at very low frequency, ~ 500 cm-1, so it does not appear in the scan.
The C-C stretching bands are weak and appear over a broad range, i.e., 1200 to 800 cm-1, and are generally of low utility (of little value for identification).
A variety of C-H stretching and bending bands appear and they are of high utility.

CH at 2960-2850 cm-1 (2 sets of split peaks, just below 3000 cm-1)

CH at 1460, 1380, and 720 cm-1

Group / Band (cm-1) / Intensity () / Assignments / Remarks
/ 2960 / s70 / as CH3
-CH3 / 2870 / m30 / s CH3
/ 1460 / m 15 / as CH3
1380 / s15 / (s CH3) umbrella / doublet in gem-dimethyls & t-butyls
2925 / s75 / as CH2 / doublet with 2960 as CH3 stretch
-CH2- / 2850 / s45 / s CH2 / doublet with 2870 s CH3 stretch
1470 / m8 / (s CH2) scissor / doublet with 1460 as CH3 bend
725-720 / s3 / (CH2)n rock / present when n  4. Higher when n < 4,
i.e., propyl 740-730, ethyl 790-770
CH3 / 1170 / s15 /  C-C (skeletal) / usually a doublet
CH- / 1385& 1370 / s15 / gem-dimethyl / doublet
CH3
CH3 / 1255 / s15 /  C-C (skeletal) / t-butyl group
CH3 - C - / 1210 / s15 /  C-C (skeletal) / t-butyl group
CH3 / 1390& 1375 / s / t-butyl / doublet
CH3 / 1195 / s15 / skeletal / quaternary C
R- C -R / 1215 / s15 / skeletal / quaternary C
CH3 / 1380 / s15 / (s CH3) umbrella

Cycloparaffins: absorption bands are much the same as acyclic paraffins provided they are unstrained, e.g., cyclohexane and cyclopentane. Ring strain in cyclopropane raises CH stretching bands from the 2960-2850 cm-1 region to the 3100-2900 cm1 region.

Halogenated Paraffins: The C-H stretch is raised above 3000 cm-1 due to the presence of electronegative halogens, e.g., CHCl3 absorbs at 3010 cm-1. The following C-X stretches are also observed ...

An aliphatic C-Cl band occurs between 850&550 cm-1. With several Cl substitutions, the band occurs at the high frequency end of the range and its intensity also increases.
A C-Br band appears @ 690-515 cm-1, C-I @ 600-500 cm-1, CH2X @ 1300-1150 cm-1
Several strong C-F bands cover the wide range of 1400-730 cm-1

OLEFINS (ALKENES)

In addition to the paraffin bands, unsaturated organics show C-H stretching bands above 3000 cm-1. They are rarely hidden by the strong main bands below 3000 cm-1. The C=C double bond absorbs sharply in the 1650 cm-1 region & C-H out-of-plane bending bands appear between 1000-650 cm-1, the exact position depending upon the substitution pattern on the double bond.

Group / Band (cm-1) / Intensity () / Assignments / Remarks
=CH2 / 3080 / m30 / as CH2 / CH > 3000 cm-1 indicates alkene or aromatic. Seen in terminal alkenes
2975 / m- / s CH2 / Overlaps with alkane absorption (not seen)
=CH-R / 3020 / m - /  CH / Seen in some internal alkenes
terminal vinyl
vinylidene / 1650
1670 / s30
s30 /  C=C / Shifts to 1670 cm-1 in cis, trans, tri- and tetra-substituted alkenes. Trans is very weak.
C=CH2
terminal vinyl / 990
910 / s50
s110 /  CH(out-of-plane wag)
C=CH2
terminal vinylidene / 890 / s125 /  CH(out-of-plane wag)
C=C
cis- / 730-675 / m40 /  CH(out-of-plane)
C=C
trans- / 965 / s100 /  CH(out-of-plane)
C=C
tri- / 840-800 / s40 /  CH(out-of-plane)
C=C
tetra- / -- / --- /  CH(out-of-plane) / absent due to symmetry (IR inactive)

Conjugated Systems: Olefinic bond stretching vibrations in conjugated olefins, without a center of symmetry, interact to produce two C=C stretching bands. For example...

1,3-pentadiene (CH2=CH-CH=CH-CH3) shows C-C stretching at 1650 cm-1 and 1600 cm-1.
Symmetrical 1,3-butadiene (CH2=CH-CH=CH2) shows only 1 band near 1600 cm-1.

AROMATICS

The presence of an aromatic group is shown by the 3030, 1600, and 1500 cm-1 bands as well as aromatic overtones and combination band patterns between 2000 and 1700 cm-1. C-H out-of-plane bending band(s) below 900 cm-1 indicates substitution patterns.

Group / Band (cm-1) / Intensity () / Assignments / Remarks
aromatic / 3030, several / m<60 /  CH and combination / Sometimes appear as a weak shoulder on the main  CH aliphatic band.
2000-1700 several / wca. 5 / combinations and
 CH overtones / Group of 2 to 6 bands characteristic of the substitution pattern
1600, (1580)
1500, (1450) / s< 100
s< 100 / phenyl nucleus / Variable intensity, 1500 usually stronger than 1600. 1580 band appears when phenyl is conjugated with unsaturated groups or atoms with lone electron pairs.
1450 peak overlaps with alkane CH band.
<900
several / m>100 / CH out-of-plane bending / Identified by comparison with scans of knowns. Vary with substitution patterns of aromatic. Electron-withdrawing groups (e.g., nitro) increase  about 30 cm-1.

Polynuclear Aromatics: have IR spectra, which are very similar to mononuclear aromatics.

XY GROUPS

The 2200 cm-1 region:

Absorptions in this region originate from the XY type groups, i.e., acetylenic (-CC-) and nitrile (-CN). They are weak but distinctive since no other bands appear in this region.
CH stretching band frequencies are significantly raised in alkynes.

Group / Band (cm-1) / Intensity () / Assignments / Remarks
acetylenic
-CC-H / ~3300 / s100 / CH / terminal alkynes.
-CC- / ~2120 / s5 /  CC / terminal alkynes.
~2220 / s1 /  CC / internal alkynes- but is completely absent when symmetry is high
-CC-H / 600-700 / m100 / CH
nitrile
-CN / ~2240 / s10-150 /  CN / aliphatic, e.g., acetonitrile (2250)
aromatic, e.g., benzonitrile (2230)

It is difficult to distinguish between internal alkynes and nitriles. Neither have  C-H at 3300 cm-1 and both have show absorption at ca. 2200 cm-1. However,  -CN at 2200 cm-1 is much more intense than  -CC because the C-to-N bond is more polar than the C-to-C bond.

ALCOHOLS AND PHENOLS

The characteristic bands are the O-H stretch, C-O stretch, and O-H bend modes. They are all sensitive to hydrogen bonding.

Free O-H stretch (dilute solns. in nonpolar solvent) produce sharp, strong absorption at 3600 cm-1. The band grows wide and moves to a lower frequency (3300 cm-1) with strong H-bonding, e.g., neat liquid samples.
Strong C-O stretch occurs at 1260-1000 cm-1.
O-H bending is seen at 1420-1050 cm-1 and below 800 cm-1.

Water of hydration or water contamination in samples produces a broad band in the same region as H-bonded O-H stretch, i.e., ~3300 cm-1.

Phenols: will show the OH and CO bands as well as aromatic bands.

Group / Band (cm-1) / Intensity () / Assignments / Remarks
Free O-H, 1
2º
3º
phenolic O-H / 3640
3630
3620
3610 / s70
s55
s45
s~50 /
 OH / In dilute, non-polar solvents such as CCl4 and CHCl3.
all H-bonded
O-H
including phenols /
3400-3200 /
w~50 /
 OH /
In neat liquids
-C-O-H / 1260-1000 / m~ 60 /  C-O / Variable position reduces utility of these strong bands.
O-H / 1420-1050
770-650 / m--
w-- /  OH in-plane
 OH out-of-plane / Variable position and possible overlap with CH in alkanes reduces utility of these bands.
In liquid alcohols and phenols

ETHERS

The mass of the oxygen atom and the strength of C-O bonds do not differ much from those of the C atom and C-C bonds, and hence the positions of ether absorptions (1150-1085 cm-1) are not characteristic - they lie in the same region as the C-C stretching bands (1200-800 cm-1). C-O stretching bands are stronger because their dipole moment change is greater than for C-C bonds.

Identification of ether groups from IR spectra is not easy because organic compounds frequently contain other C-O bonds, e.g., alcohols, esters, acids. In summary, a peak at ~ 1100 cm-1 or ~1200 cm-1 only infers the presence of a C-O bond or a =C-O bond, respectively. Band intensities are generally large, i.e., > 200.

Group / Band (cm-1) / Intensity () / Assignments / Remarks
-C-O-C / 1150-1085
/ m---
/ as C-O-C / Aliphatic C-O-C
Common with other C-O bands.
=C-O-C / 1275-1200
1075-1020 / m---
m--- / as =C-O-C
s =C-O-C / Aromatic and vinyl ethers stretch.
Weaker than the 1250 cm-1 band.

THE CARBONYL GROUP COMPOUNDS

Ketones, aldehydes, carboxylic acids, esters, acid halides, acid anhydrides, amides and lactams all show a strong C=O stretching absorption band in the 1870-1540 cm-1 region. Its relatively constant position, high intensity ( = 300-1500), and freedom from interfering bands makes this one of the easiest bands to recognize in the IR spectra.

Ketones: For neat saturated aliphatic ketones, the normal stretching vibration band occurs at 1715 cm-1. For example, acetone and cyclohexanone absorb at 1715 cm-1. Replacement of an alkyl group at the -C of a saturated ketone by a heteroatom shifts the carbonyl absorption.

Inductively withdrawing heteroatoms, i.e., the halogens, increase the C=O force constant and thus increase the carbonyl absorption frequency.
Resonance donating heteroatoms, i.e., -NH2 and -SR, have the opposite effect.

Conjugation with a C=C bond results in delocalization of the  electrons of both unsaturated groups and this reduces the double bond character causing a shift to a lower frequency.

Group /  C=O (cm-1)
Inductive Withdrawal Groups
Br / 1760
Cl / 1815-1785
F / 1870
OH / 1760
OR / 1735
Resonance Donating Group
NH2 / 1695-1650
SR / 1720-1690
conjugate (, -) unsaturation / 1685-1665
aromatic ring / 1690

Acid Halides: The spectra of acid halides are very similar to ketones with the exception that the carbonyl band of an acid halide occurs at a higher frequencies than that of a ketone. Conjugate unsaturation with acid halides lowers the carbonyl band frequency. For example, benzoyl chloride absorbs at 1770 cm-1 compared to 1800 cm-1 for most aliphatic acid chlorides.

Aldehydes: The C=O stretch of normal (aliphatic) aldehydes occurs at 1740-1720 cm-1. As in ketones, electronegative substituents on the -C increase the frequency of carbonyl absorption. For example, acetaldehyde absorbs at 1730 cm-1 and trichloroacetaldehyde at 1770 cm-1.

The distinguishing feature between an aldehyde and a ketone is that the C-H stretch of aldehydes occurs at 2820-2695 cm-1. In most aldehydes, this C-H band is split. A sharp band of medium intensity near 2720 cm-1 accompanied by a carbonyl absorption is good evidence for the presence of an aldehyde group.

Carboxylic Acids: In liquid or solid state, and even in nonpolar solutions at concentrations above 0.01 M, carboxylic acids exist as dimers due to strong hydrogen bonding.

Dimerized carboxylic acids exhibit carbonyl bands at 1710 cm-1, very close to the normal ketone band, but much more intense. The OH in carboxylic acids is easily recognized. It is very broad and lowered from its alcoholic position to 3300-2500 cm-1.

As expected, carboxylic acids show both C-O stretching and in-plane O-H bending bands in the
1400-1200 cm-1 region & broad, medium to low intensity, out-of-plane O-H bending near 920 cm-1.

Esters: Esters show strong characteristic absorption bands for C=O and C-O stretches.

 C=O for aliphatic esters at 1750-1735 cm-1

 C=O for aromatic esters at 1730-1715 cm-1

 C-O for all esters between 1300-1000 cm-1

Esters are easily distinguished from carboxylic acids since they lack the broad  O-H band.

The IR spectra of esters look similar to those of ketones and acid halides since all have absorption bands in the 1200 cm-1 region, however ester C-O stretches are larger than the C-C stretches of ketones and acid halides. Esters are difficult to distinguish from ketones. Esters have two C-O stretches (1300 - 1050 cm-1) in addition to the C-C stretch (1200 - 800 cm-1) of ketones and esters.

Acid Anhydrides: Acid anhydrides have 2 carbonyl groups joined by an O atom. Their IR spectra are unique and easy to recognize as 2 carbonyl peaks are seen. They usually appear as one split band with their tips about 60 cm-1 apart.

Saturated acyclic anhydrides absorb near 1820 and 1760 cm-1 (e.g., propionic anhydride)

Conjugated acyclic anhydrides absorb near 1775 and 1720 cm-1.

Saturated cyclic anhydrides with 5-membered rings absorb at 1865 and 1780 cm-1 (at higher frequencies due to ring strain). (e.g., succinic anhydride)

Phthalic anhydride, a conjugated aromatic anhydride absorbs at 1785 and 1760 cm-1.

As expected for acid anhydrides, strong  C-O-C bands are seen in the 1300-1050 cm-1 region.

Amides:

All amides show a carbonyl absorption band known as the amide I band. Its exact position varies (~ 1670 cm-1) but as previously stated, is lower than the normal ketone carbonyl band at 1715
cm-1 due to resonance with the unpaired electrons on N.
1º and 2º amides and some lactams, display another, weaker band in the 1650-1515 cm-1 region due to  NH. This second band, called the amide II band, is usually under the envelope of the amide I band and, on rare occasions, is completely overlapped by the amide I band and therefore not distinguishable. 3º amides do not display this band since they have no N-H bonds.
1º and 2º amides (and amines) display a broad, medium-to-weak, out-of-plane N-H rocking band in the 800-670 cm-1 region, reminiscent of the O-H rocking band in alcohols at 770-650 cm-1.
1º and 2º amides (and amines) show N-H stretching vibrations in the 3500-3300 cm-1 region, i.e., within the region of O-H stretching. N-H stretching bands however are narrower and less intense than O-H bands so they are readily recognized.

1º amides (R-CONH2) and 1º amines usually show 2 bands here for as NH2 and s NH2.

2º amides (R-CONHR’) and 2º amines show only 1 band here, corresponding to  N-H.

3º amides (R-CONR’2) and 3º amines have no N-H stretching bands.

All amides and amines also show medium-intensity C-N stretching bands over the broad range of 1400-1050 cm-1. These are difficult to distinguish but help to confirm the presence of N in a compound when interpreted with other data.

Amines: The N-H stretching and bending bands and C-N stretching bands in amines are basically the same as in amides. They are listed again along with details specific to amines.

In the 3500-3300 cm-1region, 1º amines (R-NH2) show 2  N-H bands, 2º amines (R2-NH) show 1 band and 3º amines (R3-N) have no  N-H bands.

In plane  N-H (scissoring) occurs at 1650-1500 cm-1. (Equivalent to Amide II band of
1 and 2 amides). The band is strongest in 1º amines, small and difficult to locate in 2º amines, and does not occur in 3º amines.

Out-of-plane  N-H (rocking) occurs at 910-670 cm-1. The band is strongest in 1º amines, and does not occur in 3º amines.

Medium to weak  C-N occurs at 1250-1020 cm-1in aliphatic amines. Oddly, the frequencies are increased to 1340-1265 cm-1 in aromatic amines.

Amine Salts:

Ammonium ion (NH4+ Cl - ) displays strong, broad absorption at 3300-3030 cm-1.

Salts of 1º amines (R-NH3+ Cl - ) display strong, broad absorption at 3000-2800 cm-1 with multiple combination bands of medium intensity occurring at 2800-2200 cm-1.

Salts of 2º amines (R2-NH2+ Cl - ) display strong, broad absorption at 3000-2700 cm-1 with multiple combination bands extending to 2270 cm-1.

Salts of 3º amines (R3-NH+ Cl - ) display strong, broad absorption at 2700-2250 cm-1.

Quaternary ammonium salts (R4-N+ Cl - ) can have no N-H stretching vibrations.

As expected, the 1600-1400 cm-1 region contains  N-H bands for salt of 1º, 2º, and 3º amines.

Group / Band (cm-1) / Intensity () / Assignments / Remarks
Ketone / m>300 /  C=O
-CO- / 1715 /  C=O / aliphatic, e.g., acetone
, -unsatd. / 1685 /  C=O / e.g., 3-buten-2-one (methyl vinyl ketone)
Ar-CO- / 1690 /  C=O / e.g., acetophenone (methyl phenyl ketone)
7-memb. ring / 1705 /  C=O / e.g., cycloheptanone
6-memb. ring / 1715 /  C=O / e.g., cyclohexanone
5-memb. ring / 1750 /  C=O / e.g., cyclopentanone
4-memb. ring / 1785 /  C=O / e.g., cyclobutanone
-C-C- / 1200-1000 / m~70 /  C-CO / aliphatic, e.g., acetone
-C-C- / 1300-1100 / m ~70 /  C-CO / aromatic, e.g., acetophenone
acid halide / m>300 /  C=O
R-CO-Cl / 1810 /  C=O / aliphatic acid chloride, e.g., acetyl chloride
Ar-CO-Cl / 1770 /  C=O / aromatic acid chloride, e.g., benzoyl chloride
R-CO-Br / 1760 /  C=O / aliphatic acid bromide, e.g., acetyl bromide
R-CO-I / 1725 /  C=O / aliphatic acid iodide, e.g., acetyl iodide
R-CO-F / 1870 /  C=O / aliphatic acid fluoride, e.g., acetyl fluoride
-C-C- / 1300-1000 / m~70 /  C-CO
aldehyde / m~70 /  C=O
R-CHO / 1730 /  C=O / aliphatic aldehyde, e.g., acetaldehyde
Ar-CHO / 1705 /  C=O / aromatic aldehyde, e.g., benzaldehyde
, -unsatd. / 1705 /  C=O / e.g., 2-propenal
-CHO / 2820 (2720) / s<50 /  C-H / may be one or two bands
-C-CHO / 1300-1000 / m~70 /  C-CO
acid (dimers) / m1000 /  C=O / intense,  up to 1500
R-COOH / 1710 /  C=O / aliphatic, e.g., acetic acid (1760 in monomer)
, -unsatd. / 1690 /  C=O / conjugate unsatd. aliphatic, e.g., propenoic acid
Ar-COOH / 1690 /  C=O / aromatic acid, e.g., benzoic acid
-O-H / 3300-2500 / w~70 /  O-H / very characteristic
-CO-OH / 1420 / m50 /  C-O
-CO-O-H / 1300-1200 / m50 /  CO-OH / in-plane bend
-O-H / 920 / m<50 /  O-H / out-of-plane bend
ester / m700 /  C=O / intensity between ketone and acid (500-1000)
R-CO-O-R / 1735 /  C=O / e.g., ethyl acetate
Ar-CO-O-R / 1720 /  C=O / e.g., ethyl benzoate
Ar-CO-O-Ar / 1735 /  C=O / e.g., phenyl benzoate
R-CO-O-Ar / 1775 /  C=O / e.g., phenyl acetate & vinyl acetate (, -unsat.)
-C-O / 1300& 1050 / m>700 /  C-O / occasionally appears as 1 split peak
Group / Band (cm-1) / Intensity () / Assignments / Remarks
acid anhydride / m>300 /  C=O / usually appears as a split band
-OC-O-CO- / 1820& 1760 /  C=O / aliphatic, e.g., acetic anhydride
, -unsatd. / 1775& 1720 /  C=O / e.g., 3-buten-2-one (methyl vinyl ketone)
5-memb. ring / 1865& 1780 /  C=O / e.g., succinic anhydride (ring strain)
-OC-O-CO- / 1300-1050 / m>300 /  C-O / 1 to 2 strong bands in all anhydrides
amide / amide I (II)
1º R-CO-NH2 / 1690 (1600) / 1000(300) /  C=O ( N-H) / free aliphatic, e.g., acetamide
" / 1650 (1630) / 1000(300) /  C=O ( N-H) / associated aliphatic, e.g., acetamide
1º Ar-CO-NH2 / 1675 (1600) / 1000(300) /  C=O ( N-H) / free aromatic, e.g., benzamide
1º R-CO-NH2 / 3400& 3200 / m<30 / ass N-H / usually 2 narrow bands & possible shoulder
" / 800-670 / m<30 /  N-H (rocking) / single band
2º R-CO-NRH / 1680 (1580) / 1000(300) /  C=O ( N-H) / free aliphatic, e.g., N-methylacetamide
" / 1655 (1550) / 1000(300) /  C=O ( N-H) / associated aliphatic, e.g., N-methylacetamide
" / 3350 / m<30 /  N-H / 1 band and possible shoulder to the right
" / 800-670 / m<30 /  N-H (rocking) / single band
3º R-CO-NR2 / 1650 (none) / 1000(300) /  C=O / free aliphatic, e.g., N,N-dimethylacetamide
" / 1650 (none) / 1000(300) /  C=O / assoc. aliphatic, e.g., N,N-dimethylacetamide
1º, 2º, 3º -CO-N / 1400-1050 / m<50 /  C-N (amide III) / increasing intensity from 1º 2º 3º
amine
1º R-NH2 / 3500 / m<30 / as N-H
" / 3400 / m<30 / s N-H / shoulder on low  side may look like 3rd band
" / 1650-1580 / m<50 /  N-H in-plane / (scissoring) stronger than in 2º amines
" / 910-670 / m50 /  N-H / out-of-plane bend, stronger than in 2º amines
2º R2-NH / ~3330 / m<30 /  N-H / shoulder on low  side may look like 2rd band
" / 1580-1500 / m<15 /  N-H in-plane / weak in 2º amines & buried in aromatic amines
" / 910-670 / m50 /  N-H / out-of-plane bend
1º, 2º, & 3º / 1250-1020 / m<70 /  C-N / increasing intensity from 1º 2º 3º
amine salts
NH4+ Cl- / 3300-3030 / w>100 /  N-H
R-NH3+ Cl- / 3000-2800 / w>100 /  N-H / also multiple combination bands at 2800-2200
R2-NH2+ Cl- / 3000-2700 / w>100 /  N-H / also multiple combination bands down to 2270
R3-NH+ Cl- / 2700-2250 / w>100 /  N-H
R4-N+ Cl- / none / no N-H bonds
salts of 1º, 2º, 3º / 1600-1400 / m<100 /  N-H

NITRO GROUP

Nitro groups produce two N-O stretches, a C-N stretch and a C-NO2 bend. The CNO bend occurs at 610 cm-1 and so is not seen on the usual IR scan but shifts aromatic  CH oop higher and destroys the reliability of the  CH oop for identifying substitution patterns of aromatics.

Group / Band (cm-1) / Intensity () / Assignments / Remarks
N-O / 1550& 1370 / m / as N-O& s N-O / aliphatic
1530& 1350 / m / as N-O& s N-O / conjugated
C-N / 870 / w /  C-N
C-NO2 / 610 /  C-NO2 / not seen but shifts CH oop higher

Nitro groups are difficult to identify especially in aromatic compounds where phenyl nucleus stretches occur at 1600 cm-1 and -CH3 groups absorb at 1380 cm-1. The two N-O stretches are of similar intensity and broader than the phenyl and methyl group bands just mentioned.

Interpretation of IR Spectra

For relatively simple molecules much information can be gained about its functional groups from spectral correlations. To analyze an IR spectra, 1) pay most attention to the strongest absorptions, 2) pay more attention to peaks to the left (shorter ) of 1250 cm-1, and 3) pay as much attention to the absence of certain peaks as to the presence of others. The absence of characteristic peaks will definitely exclude certain functional groups. Be wary of O-H peaks because water is a common contaminant in many samples, especially when scanned in KBr disks.

A stepwise analysis:

Is there a strong C=O stretching peak between 1820 to 1625 cm-1? If not, carbonyl groups are absent, so go to step 2. If yes, continue with a), b), c), etc.

a)Is there also a strong, broad O-H peak between 3500 and 2500 cm-1? If so, the compound is a carboxylic acid. If not then:

b)Is there a medium-to-weak N-H stretching band between 3520 to 3070 cm-1? If there are 2 peaks, then it is a primary amide. If there is only 1 peak, then it is a secondary amide. Tertiary amides do not absorb in this region since they do not have N-bonded hydrogens. Thus, if there is no absorption band, then 1 and 2 amides are eliminated and then:

c)Are there 2 strong peaks, 1 in the region 1870 to 1800 cm-1 and the other in the region 1800 to 1740 cm-1 ? If so, an acid anhydride is present. If not:

d)Is there a weak-to-medium, narrow peak in the region of 2720 cm-1 ? If so, is the carbonyl peak in the region 1715 to 1680 cm-1 ? If so, it is a conjugated aldehyde; if not, it is an isolated aldehyde. However, if there is not a peak near 2720 cm-1:

e)Does the strong carbonyl peak fall in the range 1815 to 1770 cm-1 and the molecule give a positive Beilstein test? If so, it is an acid halide. If not:

f)Does the strong carbonyl peak fall in the range 1690 to 1675 cm-1? If so, if so it is a conjugated ketone. If not:

g)Does the strong carbonyl peak fall in the range 1670 to 1630 cm-1 ? If so, it is a tertiary amide. If not:

h)Does the molecule have a strong, wide peak in the range 1310 to 1100 cm-1 ? If so, does the carbonyl peak fall in the range 1730 to 1715 cm-1 ? If so, it is a conjugated ester; if not, the ester is not conjugated. If there is not a strong, wide peak in the range 1310 to 1100 cm-1, then:

i)The molecule is an ordinary, nonconjugated ketone.

If the molecule lacks a carbonyl peak in the range 1820 to 1625 cm-1, does it have a broad O-H band in the region 3650 to 3200 cm-1 ? If so, does it also have a secondary alcohol peak about 1200 cm-1, a C-H stretching peak to the left of 3000 cm-1, and a phenyl group peak in the region 1600 to 1470 cm-1 ?. If so, it is a phenol. If it does not meet these latter 3 criteria, it is an alcohol. However, if there is no broad band in the region 3650 to 3200 cm-1, then it is not an alcohol, so:

a)Is there a moderately broad band in the region 3500 to 3300 cm-1, does the molecule smell like an amine, or does it contain nitrogen? If so, are there 2 peaks in this region? If so, it is a primary amine: if not, it is a secondary amine. However, if there is no broad band in the region 3500 to 3300 cm-1, then:

b)Is there a sharp peak of medium-to-weak intensity at 2260 to 2100 cm-1 ? If so, is there also a CC-H stretching peak at 3320 to 3310 cm-1 ? If so, the molecule is a terminal acetylene. If not, then the molecule is most likely a nitrile, although it may be a substituted acetylene. If there is no sharp peak of medium-to-weak intensity at 2260 to 2100 cm-1 , then: