Chem-805

Chem-805

Identification of organic and

Identification of organic and

inorganic compounds by

inorganic compounds by

spectroscopy

spectroscopy

Mass
Spectrometry
NMR



Infrared

Infrared

Infrared

Infrared

10,000 cm

10,000 cm

-1

-1

to 100 cm

to 100 cm

-1

-1

Converted in Vibrational energy in molecules

Converted in Vibrational energy in molecules

Vibrational Spectra appears as bands instead of sharp
lines => as it is accompanied by a number of rotational
changes

Wave Number

=>





(cm

-1

) => proportional to energy





Depends on:

•Relative masses of atoms

•Force constant of bonds

•Geometry of atoms

Older system uses the wavelenght





(m => 10

-6

m)

cm

-1

= 10

4

/ m

The Units:

The Units:

The frequency  (s

-1

) => # vibrations per second

For molecular vibrations, this number is very large (10

13

s

-1

)

=> inconvenient

More convenient : Wavenumber









=



c

(

Frequency

/

Velocity

)

e.g. 



= 3 * 10

= 3 * 10

13

13

s

s

-1

-1









=











s



3 * 10

10

cm s

-1

= 1000 cm

= 1000 cm

-1

-1

Wave Length :





1









=

Intensity:

Intensity:

Transmittance (T

T

) or %T

%T

T

T

=

I

I

0

Absorbance (A

A

)

A

A

= log I

I

0

Intensity in IR

Intensity in IR

IR

IR

: Plot of %IR

%IR

that passes through a sample (transmittance

transmittance

)

vs Wavelenght

Wavelenght

Infrared

Infrared

• Position, Intensity and Shape of bands

gives clues on Structure of molecules

• Modern IR uses Michelson Interferometer

=>

involves computer, and Fourier Transform

Sampling

Sampling

=> plates, polished windows, Films …

Must be transparent in IR

NaCl, KCl : Cheap, easy to polish

NaCl, KCl : Cheap, easy to polish

NaCl

NaCl

transparent to 4000 - 650 cm

4000 - 650 cm

-1

-1

KCl

KCl

transparent to 4000 - 500 cm

4000 - 500 cm

-1

-1

KBr

KBr

transparent to 400 cm

400 cm

-1

-1

Infrared: Low frequency spectra

Infrared: Low frequency spectra

of window materials

of window materials

Bond length and strength

Bond length and strength

vs

vs

Stretching frequency

Stretching frequency

Bond

C-H

=C-H

-C-H

Length

1.08

1.10

1.12

Strenght

506 kJ

444 kJ

422 kJ

IR freq.

3300 cm

-1

3100 cm

-1

2900 cm

-1

Introduction

Introduction

IR is one of the first technique inorganic chemists used
(since 1940)

Molecular Vibration

Molecular Vibration

Newton’s law of motion is used classically to calculate
force constantr

r

e

F

F

F

F

The basic picture : atoms
(mass) are connected with
bonding electrons. R

e

is the

equilibrium distance and F

F

:

force to restore equilibrium

F(x) = -

k

x

where X is displacement from equilibrium









=

=

1

1

2

2





√

k

k

i

i





i

i

Where

Where k

k

i

i

is the force constant and

is the force constant and 



i

i

is reduce mass of a particular motion

is reduce mass of a particular motion

Because the energy is quantized: E =

Because the energy is quantized: E =

h

h





i

i

Introduction

Introduction

Displacement of atoms during vibration lead to

Displacement of atoms during vibration lead to

distortion of electrival charge distribution of the

distortion of electrival charge distribution of the

molecule which can be resolve in dipole,

molecule which can be resolve in dipole,

quadrupole, octopole …. In various directions

quadrupole, octopole …. In various directions

=> Molecular vibration lead to oscillation of

=> Molecular vibration lead to oscillation of

electric charge governed by vibration frequencies

electric charge governed by vibration frequencies

of the system

of the system

Oscillating molecular dipole can interact directly

Oscillating molecular dipole can interact directly

with oscillating electric vector of electromagnetic

with oscillating electric vector of electromagnetic

radiation of the same frequency

radiation of the same frequency

h

h





=

= h

h





Vibrations are in the range

Vibrations are in the range

10

10

11

11

to 10

to 10

13

13

Hz

Hz

=>

=>

30 - 3,000 cm

30 - 3,000 cm

-1

-1

Introduction: Symmetry

Introduction: Symmetry

selection rule

selection rule

Stretching homonuclear diatomic molecule like

Stretching homonuclear diatomic molecule like N

N

2

2

does not generate oscillating dipole

does not generate oscillating dipole



Direct interaction with oscillating electronic Dipole is not

Direct interaction with oscillating electronic Dipole is not

possible

possible



inactive in IR

inactive in IR

There is no place here to treat fundamentals of symmetry

There is no place here to treat fundamentals of symmetry

In principle, the symmetry of a vibration need to be determined

In principle, the symmetry of a vibration need to be determined

Calculating stretching frequencies

Calculating stretching frequencies

Hooke’s law :

Hooke’s law :





=

=

1

1

2

2





c

c



k

k









: Frequency in cm

: Frequency in cm

-1

-1

c : Velocity of light => 3 * 10

c : Velocity of light => 3 * 10

10

10

cm/s

cm/s

k

k

: Force constant => dynes /cm

: Force constant => dynes /cm





masses of atoms in grams

masses of atoms in grams





m

m

1

1

m

m

2

2

m

m

1

1

+ m

+ m

2

2





M

M

1

1

M

M

2

2

M

M

1

1

+ M

+ M

2

2

(6.02 * 10

(6.02 * 10

23

23

)

)





=

=

4.12

4.12



k

k





C

C

-

-

C

C k

k

= 5* 10

= 5* 10

5

5

dynes/cm

dynes/cm

C

C

=C

=C k

k

= 10* 10

= 10* 10

5

5

dynes/cm

dynes/cm

C

C





C

C k

k

= 15* 10

= 15* 10

5

5

dynes/cm

dynes/cm

Calculating stretching frequencies

Calculating stretching frequencies

C

C

=C

=C K = 10* 10

K = 10* 10

5

5

dynes/cm

dynes/cm





=

=

4.12

4.12



K

K











 M

M

1

1

M

M

2

2

M

M

1

1

+ M

+ M

2

2





(12)(12)

(12)(12)

12 + 12

12 + 12













=

=

4.12

4.12



10* 10

10* 10

5

5





= 1682 cm

= 1682 cm

-1

-1





Experimental

Experimental





1650 cm

1650 cm

-1

-1

C

C

—H

—H K = 5* 10

K = 5* 10

5

5

dynes/cm

dynes/cm





=

=

4.12

4.12



5* 10

5* 10

5

5









= 3032 cm

= 3032 cm

-1

-1







 M

M

1

1

M

M

2

2

M

M

1

1

+ M

+ M

2

2





(12)(1)

(12)(1)

12 + 1

12 + 1



 

 



 









Experimental

Experimental





3000 cm

3000 cm

-1

-1

C

C

—D

—D K = 5* 10

K = 5* 10

5

5

dynes/cm

dynes/cm





=

=

4.12

4.12



5* 10

5* 10

5

5





= 2228 cm

= 2228 cm

-1

-1







 M

M

1

1

M

M

2

2

M

M

1

1

+ M

+ M

2

2





(12)(2)

(12)(2)

12 + 2

12 + 2



 















Experimental

Experimental





2206 cm

2206 cm

-1

-1

Vibration

Vibration

s

s

www.cem.msu.edu/~reusch/Virtual/Text/Spectrpy/InfraRed/infrared.htm

Modes of vibration

Modes of vibration

C

C

—H

—H

Stretching

Stretching

Bending

Bending

C

C

O

O

H

H

H

H

Symmetrical

Symmetrical

2853 cm

2853 cm

-1

-1

H

H

Asymmetrical

Asymmetrical

2926 cm

2926 cm

-1

-1

H

H

H

H

Scissoring

Scissoring

1450 cm

1450 cm

-1

-1

Rocking

Rocking

720 cm

720 cm

-1

-1

H

H

H

H

Wagging

Wagging

1350 cm

1350 cm

-1

-1

Twisting

Twisting

1250 cm

1250 cm

-1

-1

Stretching

Stretching

frequency

frequency

Bending

Bending

frequency

frequency

Vibration

Vibration

s

s

www.cem.msu.edu/~reusch/Virtual/Text/Spectrpy/InfraRed/infrared.htm

General trends:

General trends:

•

Stretching frequencies

Stretching frequencies

are higher than

are higher than bending

bending

frequencies

frequencies

(it is easier to bend a bond than stretching or compresing them)

(it is easier to bend a bond than stretching or compresing them)

•

Bond involving Hydrogen are higher in freq. than with

Bond involving Hydrogen are higher in freq. than with

heavier atoms

heavier atoms

•

Triple bond

Triple bond

have higher freq than

have higher freq than double bond

double bond

which

which

has higher freq than

has higher freq than single bond

single bond

Structural Information from

Structural Information from

Vibration Spectra

Vibration Spectra

•

Spectrum can be treated as finger print to

Spectrum can be treated as finger print to

recognize the product of a reaction as a known

recognize the product of a reaction as a known

compound. (require access to a file of standard

compound. (require access to a file of standard

spectra)

spectra)

•

At another extreme , different bands observed can

At another extreme , different bands observed can

be used to deduce the symmetry of the molecule

be used to deduce the symmetry of the molecule

and force constants corresponding to vibrations.

and force constants corresponding to vibrations.

•

At intermediate levels, deductions may be drawn

At intermediate levels, deductions may be drawn

about the presence/absence of specific groups

about the presence/absence of specific groups

The symmetry of a molecule determines the number of bands expected

The symmetry of a molecule determines the number of bands expected

Number of bands can be used to decide on symmetry of a molecule

Number of bands can be used to decide on symmetry of a molecule

Th

Th

e

e

task of assignment is complicated by presence of low

task of assignment is complicated by presence of low

intensity bands and presence of forbidden overtone and

intensity bands and presence of forbidden overtone and

combination bands.

combination bands.

There are different levels at which information from IR can

There are different levels at which information from IR can

be analyzed to allow identification of samples:

be analyzed to allow identification of samples:

Methods of analyzing an IR

Methods of analyzing an IR

spectrum

spectrum

The effect of

The effect of isotopic substitution

isotopic substitution

on the

on the

observed spectrum

observed spectrum

Can give valuable information about the atoms

Can give valuable information about the atoms

involved in a particular vibration

involved in a particular vibration

1.

1.

Comparison with standard spectra : traditional

Comparison with standard spectra : traditional

approach

approach

2.

2.

Detection and Identification of impurities

Detection and Identification of impurities
if the compound have been characterized before, any
bands that are not found in the pure sample can be
assigned to the impurity

(provided that the 2 spectrum are recorded with identical
conditions: Phase, Temperature, Concentration)

3.

3.

Quantitative Analysis of mixture

Quantitative Analysis of mixture

Transmittance spectra = I/I

0

x 100

=> peak height

is not lineraly related to intensity of absorption

In Absorbance A=ln (I

o

/I)

=> Direct measure of

intensity

Analyzing an IR spectrum

Analyzing an IR spectrum

In practice, there are similarities between

In practice, there are similarities between

frequencies of molecules containing similar groups.

frequencies of molecules containing similar groups.

Group - frequency correlations

Group - frequency correlations

have been

have been

extensively developed for organic compounds and

extensively developed for organic compounds and

some have also been developed for inorganics

some have also been developed for inorganics

Hydrog

Hydrog

en bond

en bond

and

and

C=O

C=O

Intensity of C=O vs

Intensity of C=O vs

C=C

C=C

Band Shape: OH vs

Band Shape: OH vs

NH2 vs CH

NH2 vs CH

Free OH and Hydrogen bonded

Free OH and Hydrogen bonded

OH

OH

Symmetrical and asymmetrical stretch

Symmetrical and asymmetrical stretch

Methyl

Methyl

2872 cm

2872 cm

-1

-1

Symmetrical Stretch

Symmetrical Stretch

Asymmetrical Stretch

Asymmetrical Stretch

—

—

C

C

—

—

H

H

H

H

H

H

—

—

C

C

—

—

H

H

H

H

H

H

Anhydride

Anhydride

O

O

O

O

O

O

1760 cm

1760 cm

-1

-1

2962 cm

2962 cm

-1

-1

1800 cm

1800 cm

-1

-1

O

O

O

O

O

O

Amino

Amino

Nitro

Nitro

—

—

N

N

H

H

H

H

3300 cm

3300 cm

-1

-1

3400 cm

3400 cm

-1

-1

1350 cm

1350 cm

-1

-1

1550 cm

1550 cm

-1

-1

—

—

N

N

H

H

H

H

—

—

N

N

O

O

O

O

—

—

N

N

O

O

O

O

General IR comments

General IR comments

Precise treatment of vibrations in molecule is not feasible here

Precise treatment of vibrations in molecule is not feasible here

Some information from IR is also contained in MS and NMR

Some information from IR is also contained in MS and NMR

Certain bands occur in

Certain bands occur in narrow regions

narrow regions

:

: OH

OH

,

, CH

CH

,

, C=O

C=O

Detail of the structure is revealed by the

Detail of the structure is revealed by the exact position

exact position

of the band

of the band

e.g.

e.g. Ketones

Ketones

O

1715 cm

1715 cm

-1

-1

CH

O

CH

2

1680 cm

1680 cm

-1

-1

Region 4000 – 1300 : Functional group

Region 4000 – 1300 : Functional group

Absence of band in this region can be used to deduce absence of groups

Absence of band in this region can be used to deduce absence of groups

Caution: some bands can be very broad because of hydrogen bonding

Caution: some bands can be very broad because of hydrogen bonding

e.g.

e.g. Enols v.broad OH, C=O absent!!

Enols v.broad OH, C=O absent!!

Weak bands in high frequency are extremely useful : S-H, C

Weak bands in high frequency are extremely useful : S-H, C





C, C

C, C





N

N

Lack of strong bands in 900-650 means no aromatic

Lack of strong bands in 900-650 means no aromatic

Alkanes

Alkanes

,

,

Alkenes

Alkenes

,

,

Alkynes

Alkynes

C-H :

C-H : <3000 cm

<3000 cm

-1

-1

>3000 cm

>3000 cm

-1

-1

3300 cm

3300 cm

-1

-1

sharp

sharp

C-C

C-C

Stretch

Stretch

Not useful

Not useful

C=C

C=C

C

C





C

C

1660-1600 cm

1660-1600 cm

-1

-1

conj. Moves to lower values

conj. Moves to lower values

Symmetrical : no band

Symmetrical : no band

2150 cm

2150 cm

-1

-1

conj. Moves to lower values

conj. Moves to lower values

Weak but very useful

Weak but very useful

Symmetrical no band

Symmetrical no band

Bending

Bending

CH

CH

2

2

Rocking

Rocking

720 cm

720 cm

-1

-1

indicate

indicate

Presence of 4-CH

Presence of 4-CH

2

2

1000-700 cm

1000-700 cm

-1

-1

Indicate substitution

Indicate substitution

pattern

pattern





C-H ~630 cm

C-H ~630 cm

-1

-1

Strong and broad

Strong and broad

Confirm triple bond

Confirm triple bond

Alkane

Alkane

Alkene :

Alkene :

1-Decene

1-Decene

To give rise to absorption of IR

To give rise to absorption of IR

=> Oscillating

Oscillating

Electric Dipole

Electric Dipole

Symmetry

Symmetry

Molecules with Center of symmetry

Molecules with Center of symmetry

Symmetric vibration => inactive

Symmetric vibration => inactive

Antisymmetric vibration => active

Antisymmetric vibration => active

Alkene

Alkene

In large molecule local symmetry produce

In large molecule local symmetry produce weak or absent vibration

weak or absent vibration

C=C

C=C

R

R

R

R

trans

trans

C=C isomer -> weak in IR

C=C isomer -> weak in IR

Observable in Raman

Observable in Raman

Alkene: Factors influencing vibration

Alkene: Factors influencing vibration

frequency

frequency

1- Strain move peak to right (decrease )

1- Strain move peak to right (decrease )

C

C

C

C

C

C

angle

angle

1650

1650

1646

1646

1611

1611

1566

1566

1656 : exception

1656 : exception

2- Substitution increase

2- Substitution increase









3- conjugation decrease

3- conjugation decrease





C=C-Ph 1625 cm

C=C-Ph 1625 cm

-1

-1

1566

1566

1641

1641

1675

1675

1611

1611

1650

1650

1679

1679

1646

1646

1675

1675

1681

1681

Alkene: Out-of-Plane bending

Alkene: Out-of-Plane bending

This region can be used to deduce substitution pattern

This region can be used to deduce substitution pattern

Alkyne:

Alkyne:

1-Hexyne

1-Hexyne

Alkyne:

Alkyne:

Symmet

Symmet

ry

ry

In IR, Most important transition

In IR, Most important transition

involve :

involve :

Ground State (

Ground State (





i

i

= 0)

= 0)

to

to First Excited State (

First Excited State (





i = 1)

i = 1)

Transition

Transition (

(





i

i

= 0)

= 0)

to

to (

(





J

J

= 2)

= 2)

=> Overtone

=> Overtone

IR : Aromatic

IR : Aromatic

=C-H

=C-H

> 3000 cm

> 3000 cm

-1

-1

C=C

C=C

1600 and 1475 cm

1600 and 1475 cm

-1

-1

=C-H

=C-H

out of plane bending: great utility to assign ring substitution

out of plane bending: great utility to assign ring substitution

overtone

overtone

2000-1667: useful to assign ring substitution

2000-1667: useful to assign ring substitution

e.g. Naphthalene:

e.g. Naphthalene:

Substitution pattern

Substitution pattern





Isolated H

Isolated H

862-835

862-835

835-805

835-805

760-735

760-735

2 adjacent H

2 adjacent H

4 adjacent H

4 adjacent H

out of plane bending

out of plane bending

Aromatic substitution: Out of

Aromatic substitution: Out of

plane bending

plane bending

Aromatic substitution: Out of

Aromatic substitution: Out of

plane bending

plane bending

Aromatic and Alkene

Aromatic and Alkene

substitution

substitution

IR: Alcohols and Phenols

IR: Alcohols and Phenols

O-H Free : Sharp 3650-3600

O-H Free : Sharp 3650-3600

O-H H-Bond : Broad 3400-3300

O-H H-Bond : Broad 3400-3300

Intermolecular Hydrogen bonding Increases with concentration
=> Less “Free” OH

Less “Free” OH

IR: Alcohols and Phenols

IR: Alcohols and Phenols

C-O : 1260-1000 cm

C-O : 1260-1000 cm

-1

-1

(coupled to C-C => C-C-O)

(coupled to C-C => C-C-O)

C-O Vibration is sensitive to substitution:

C-O Vibration is sensitive to substitution:

Phenol

Phenol

1220

1220

3` Alcohols

3` Alcohols

1150

1150

2` Alcohols

2` Alcohols

1100

1100

1` Alcohols

1` Alcohols

1050

1050

More complicated than above: shift to lower Wavenumber

More complicated than above: shift to lower Wavenumber

With unsaturation (Table 3.2)

With unsaturation (Table 3.2)

Alcohol

Alcohol

C-O : 1040 cm

C-O : 1040 cm

-1

-1

indicate primary alcohol

indicate primary alcohol

Benzyl Alcohol

Benzyl Alcohol

OH

OH

sp

sp

2

2

sp

sp

3

3

Ph

Ph

overtone

overtone

C-O : 1080, 1022 cm

C-O : 1080, 1022 cm

-1

-1

: primary OH

: primary OH

Mono

Mono

Subst. Ph

Subst. Ph

735 & 697 cm

735 & 697 cm

-1

-1

Phenol

Phenol

OH

OH

sp

sp

2

2

Ph

Ph

overtone

overtone

C=C stretch

C=C stretch

Ph-O : 1224 cm

Ph-O : 1224 cm

-1

-1

Mono

Mono

Subst. Ph

Subst. Ph

out-of plane

out-of plane

810 & 752 cm

810 & 752 cm

-1

-1

Phenol

Phenol

IR: Ether

IR: Ether

C-O-C

C-O-C

=>

=>

1300-1000 cm

1300-1000 cm

-1

-1

Ph-O-C

Ph-O-C

=>

=>

1250 and 1040 cm

1250 and 1040 cm

-1

-1

Aliphatic

Aliphatic

=>

=>

1120 cm

1120 cm

-1

-1

C=C in vinyl Ether

C=C in vinyl Ether

=>

=>

1660-1610 cm

1660-1610 cm

-1

-1

appear as Doublet => rotational isomers

appear as Doublet => rotational isomers

C

H

2

CH

O

CH

3

~1620

~1620

~1640

~1640

H

2

C

CH

O

CH

3

H

2

C

CH

O

C

H

3

Ether

Ether

sp

sp

2

2

sp

sp

3

3

Ph

Ph

overtone

overtone

C=C stretch

C=C stretch

Ph-O-C : 1247 cm

Ph-O-C : 1247 cm

-1

-1

Asymmetric

Asymmetric

stretch

stretch

Ph-O-C : 1040 cm

Ph-O-C : 1040 cm

-1

-1

Symmetric

Symmetric

stretch

stretch

Mono

Mono

Subst. Ph

Subst. Ph

out-of plane

out-of plane

784, 754 & 692

784, 754 & 692

cm

cm

-1

-1

O

H

CH

C

H

3

C

H

3

CH

3

O

IR: Carbonyl

IR: Carbonyl

From 1850 – 1650 cm

From 1850 – 1650 cm

-1

-1

Ketone 1715 cm

Ketone 1715 cm

-1

-1

is used as reference point for comparisons

is used as reference point for comparisons

1715

1715





1690

1690

1725

1725





1700

1700

1710

1710





1680

1680

1810

1810

Anhydr

Anhydr

Band

Band

1800

1800

Acid

Acid

Chloride

Chloride

1760

1760

Anhydr

Anhydr

Band 2

Band 2

1735

1735

Ester

Ester

1725

1725

Aldehyde

Aldehyde

1715

1715

Ketone

Ketone

1710

1710

Acid

Acid

1690

1690

Amide

Amide

Factor influencing

Factor influencing C=O

C=O

1) conjugation

1) conjugation

C=C

C=C

C

C

O

O

C

C

+

+

—

—

C

C

C

C

O

O

-

-

Conjugation increase single bond character of

Conjugation increase single bond character of

C=O

C=O





Lower force constant

Lower force constant





lower frequency number

lower frequency number

O

OH

Ketone and Conjugation

Ketone and Conjugation





Conjugation: Lower

Conjugation: Lower

Ketone and Ring

Ketone and Ring

Strain

Strain





Ring Strain: Higher

Ring Strain: Higher

Factors influencing

Factors influencing C=O

C=O

2) Ring size

2) Ring size

O

1715 cm

1715 cm

-1

-1

Angle ~ 120

Angle ~ 120

o

o

C

H

3

C

H

3

O

O

1751 cm

1751 cm

-1

-1

< 120

< 120

o

o

O

1775 cm

1775 cm

-1

-1

<< 120

<< 120

o

o

Factors influencing carbonyl:

Factors influencing carbonyl:

C=O

C=O

3)

3)





substitution effect (Chlorine or other halogens)

substitution effect (Chlorine or other halogens)

—

—

C

C—

—

C

C

—

—

X

X

O

O

Result in stronger bound

Result in stronger bound 



higher frequency

higher frequency





O

Cl

1750 cm

1750 cm

-1

-1

4) Hydrogen bonding

4) Hydrogen bonding

Decrease

Decrease

C=O

C=O

strenght

strenght





lower frequency

lower frequency

O

O

CH

3

O

H

1680 cm

1680 cm

-1

-1

Enol

Enol

Factors influencing carbonyl:

Factors influencing carbonyl:

C=O

C=O

5) Heteroatom

5) Heteroatom

Y

R

O

Inductive effect

Inductive effect

Stronger bond

Stronger bond

higher frequency

higher frequency

e.g. ester

e.g. ester

Y

R

O

Resonance effect

Resonance effect

Weaker bond

Weaker bond

Lower frequence

Lower frequence

e.g. amides

e.g. amides

Y

Y

C=O

C=O

Cl

Cl

Br

Br

OH (monomer)

OH (monomer)

OR (Ester)

OR (Ester)

1815-1785

1815-1785

1812

1812

1760

1760

1705-1735

1705-1735

NH2

NH2

SR

SR

1695-1650

1695-1650

1720-1690

1720-1690

inductive

inductive

resonance

resonance

Ester Carbonyl

Ester Carbonyl

Esters

Esters

C=O

C=O





~ 1750 – 1735 cm

~ 1750 – 1735 cm

-1

-1

O-C : 1300 – 1000 2 or more bands

O-C : 1300 – 1000 2 or more bands

Conjugation => lower freq.

R

OR

O

Inductive effect with

Inductive effect with

O

O

reinforce carbonyl =>

higher

higher





Conjugation with

Conjugation with

CO

CO

weaken carbonyl =>

Lower

Lower





Ester carbonyl:

Ester carbonyl:

C=O

C=O

Ester carbonyl:

Ester carbonyl:

C=O

C=O

C=O : 1765 cm

C=O : 1765 cm

-1

-1

C-O 1215 cm

C-O 1215 cm

-1

-1

1193 cm

1193 cm

-1

-1

sp

sp

2

2

C=O

C=O

Ester carbonyl:

Ester carbonyl:

C=O

C=O

Ester carbonyl : effect of

Ester carbonyl : effect of

conjugation

conjugation

Lactone carbonyl:

Lactone carbonyl:

C=O

C=O

Lactones

Lactones





Cyclic Ester

Cyclic Ester

O

O

1735

1735

1720

1720

1760

1760

1770

1770

1750

1750

1800

1800

O

O

O

O

O

O

O

O

O

O

Carbonyl compounds : Acids

Carbonyl compounds : Acids

Carboxylic acid

Carboxylic acid

Exist as dimer :

Exist as dimer :

C

H

3

C

OH

O

CH

3

C

O

H

O

Strong Hydrogen bond

Strong Hydrogen bond

OH : Very broad

OH : Very broad





3400 – 2400 cm

3400 – 2400 cm

-1

-1

C=O : broad

C=O : broad





1730 – 1700 cm

1730 – 1700 cm

-1

-1

C

C

—

—

O : 1320 – 1210 cm

O : 1320 – 1210 cm

-1

-1

Medium intensity

Medium intensity

Carbonyl compounds : Acids

Carbonyl compounds : Acids

C=O

C=O

OH

OH

C=O : 1711 cm

C=O : 1711 cm

-1

-1

OH : Very Broad 3300 to 2500 cm

OH : Very Broad 3300 to 2500 cm

-1

-1

C-O : 1285, 1207 cm

C-O : 1285, 1207 cm

-1

-1

Anhydride

Anhydride

s

s

C

H

3

O

O

CH

3

O

C=O always has 2 bands:

C=O always has 2 bands:

1830-1800 and 1775-1740 cm

1830-1800 and 1775-1740 cm

-1

-1

C

C

—O multiple bands 1300 – 900 cm

—O multiple bands 1300 – 900 cm

-1

-1

Carbonyl compounds : Aldehydes

Carbonyl compounds : Aldehydes

Aldehydes

Aldehydes

C=O

C=O





~ 1725 cm

~ 1725 cm

-1

-1

O=C-H : 2 weak bands 2750, 2850 cm

O=C-H : 2 weak bands 2750, 2850 cm

-1

-1

Conjugation => lower freq.

C=O : 1724 cm

C=O : 1724 cm

-1

-1

Carbonyl compounds : Aldehydes

Carbonyl compounds : Aldehydes

Aldehydes

Aldehydes

Other carbonyl

Other carbonyl

Amides

Amides

Lactams

Lactams

Acid Chlorides

Acid Chlorides

C=O ~1680-1630 cm

C=O ~1680-1630 cm

-1

-1

(band I)

(band I)

NH

NH

2

2

~ 3350 and 3180 cm

~ 3350 and 3180 cm

-1

-1

(stretch)

(stretch)

NH ~ 3300 cm

NH ~ 3300 cm

-1

-1

(stretch)

(stretch)

NH ~ 1640-1550 cm

NH ~ 1640-1550 cm

-1

-1

(bending)

(bending)

NH

O

R

R

—

—

C

C

—

—

Cl

Cl

O

O

1810-1775 cm

1810-1775 cm

-1

-1

C

C

—

—

Cl 730 – 550 cm

Cl 730 – 550 cm

-1

-1

~1660

~1660

NH

O

~1705

~1705

NH

O

~1745

~1745





Increase with strain

Increase with strain

Amides

Amides

NH

NH

2

2

: Symmetrical stretch =>3170 cm

: Symmetrical stretch =>3170 cm

-1

-1

asymmetrical stretch => 3352 cm

asymmetrical stretch => 3352 cm

-1

-1

C=O : 1640 cm

C=O : 1640 cm

-1

-1

NH Out of plane

NH Out of plane

Amides

Amides

Acid Chlorides

Acid Chlorides

Amino acid

Amino acid

Exist as zwitterions

Exist as zwitterions

C

C

CO

CO

2

2

-

-

NH

NH

3

3

+

+

NH

NH

3

3

+

+

: very broad 3330-2380

: very broad 3330-2380

(OH +

(OH + NH

NH

3

3

+

+

)

)

C

C

O

O

O

O

1600 – 1590 strong

1600 – 1590 strong

Amino acid

Amino acid

Amine

Amine

NH 3500 – 3300 cm

NH 3500 – 3300 cm

-1

-1

NH : 2 bands

NH : 2 bands

NH : 1 band

NH : 1 band

NH bending : 1650 – 1500 cm

NH bending : 1650 – 1500 cm

-1

-1

C-N : 1350 – 1000 cm

C-N : 1350 – 1000 cm

-1

-1

NH out-of-plane : ~ 800 cm

NH out-of-plane : ~ 800 cm

-1

-1

Amine salt

Amine salt

NH

NH

+

+

3500 – 3030 cm

3500 – 3030 cm

-1

-1

broad / strong

broad / strong

Ammonium

Ammonium





primary

primary





secomdary

secomdary













right

right

Left

Left

Amine

Amine

Primary Amine

Primary Amine

Secondary Amine

Secondary Amine

Tertiary Amine

Tertiary Amine

Aromatic Amine

Aromatic Amine

Other Nitrogen Compounds

Other Nitrogen Compounds

Nitriles

Nitriles

Isocyanates

Isocyanates

Isothiocyanates

Isothiocyanates

Imines / Oximes

Imines / Oximes

R-C

R-C





N :

N :

Sharp 2250 cm

Sharp 2250 cm

-1

-1

Conjugation moves to lower frequency

Conjugation moves to lower frequency

R-N=C=O

R-N=C=O

Broad ~ 2270 cm

Broad ~ 2270 cm

-1

-1

R-N=C=S

R-N=C=S

2 Broad peaks ~ 2125 cm

2 Broad peaks ~ 2125 cm

-1

-1

R

R

2

2

C=N-R

C=N-R

1690 - 1640 cm

1690 - 1640 cm

-1

-1

Nitrile

Nitrile

C

N

CH



Nitrile

Nitrile

Nitrile and Isocyanate

Nitrile and Isocyanate

Nitro

Nitro

—

—

N

N

O

O

O

O

+

+

-

-

Aliphatic :

Aliphatic :

Asymmetric : 1600-1530 cm

Asymmetric : 1600-1530 cm

-1

-1

Symmetric : 1390-1300 cm

Symmetric : 1390-1300 cm

-1

-1

Aromatic :

Aromatic :

Asymmetric : 1550-1490 cm

Asymmetric : 1550-1490 cm

-1

-1

Symmetric : 1355-1315 cm

Symmetric : 1355-1315 cm

-1

-1

Nitro

Nitro

Nitro

Nitro

Sulfur

Sulfur

Mercaptans

Mercaptans

S – H : weak 2600-2550 cm

S – H : weak 2600-2550 cm

-1

-1

Since only few absorption in that range it confirm its presence

Since only few absorption in that range it confirm its presence

Sulfides,Disulfides : no useful information

Sulfides,Disulfides : no useful information

Sulfoxides:

Sulfoxides:

R

S

R

O

Strong ~ 1050 cm

Strong ~ 1050 cm

-1

-1

Sulfones

Sulfones

:

:

Asymetrical ~ 1300 cm

Asymetrical ~ 1300 cm

-1

-1

Symetrical ~ 1150 cm

Symetrical ~ 1150 cm

-1

-1

R

S

R

O

O

2 bands :

2 bands :

Sulfur: Mercaptan R-

Sulfur: Mercaptan R-

S-H

S-H

Sulfur: Sulfonyl Chloride

Sulfur: Sulfonyl Chloride

S=O :

S=O :

Asymmetrical stretch: 1375 cm-1

Asymmetrical stretch: 1375 cm-1

Symmetrical Stretch : 1185 cm-1

Symmetrical Stretch : 1185 cm-1

Sulfur: Sulfonate

Sulfur: Sulfonate

S=O :

S=O :

Asymmetrical stretch: 1350 cm-1

Asymmetrical stretch: 1350 cm-1

Symmetrical Stretch : 1175 cm-1

Symmetrical Stretch : 1175 cm-1

S-O : several bands between 1000 – 750 cm

S-O : several bands between 1000 – 750 cm

-1

-1

Sulfur: Sulfonamide

Sulfur: Sulfonamide

S=O :

S=O :

Asymmetrical stretch: 1325 cm-1

Asymmetrical stretch: 1325 cm-1

Symmetrical Stretch : 1140 cm-1

Symmetrical Stretch : 1140 cm-1

NH

NH

2

2

stretch: 3350 and 3250 cm

stretch: 3350 and 3250 cm

-1

-1

NH Bend: 1550 cm

NH Bend: 1550 cm

-1

-1

Halogens

Halogens

C

C

—F : 1400 – 1000 cm

—F : 1400 – 1000 cm

-1

-1

C

C

—Cl : strong 785 – 540 cm

—Cl : strong 785 – 540 cm

-1

-1

C

C

—Br : 650 – 510 cm

—Br : 650 – 510 cm

-1

-1

(out of range with NaCl plates)

(out of range with NaCl plates)

C

C

—I : 600 – 485 cm

—I : 600 – 485 cm

-1

-1

(out of range)

(out of range)

Halogens

Halogens

Phosphorus

Phosphorus

Phosphines: R-PH

Phosphines: R-PH

2

2

R

R

2

2

PH

PH

P

P

—H : Sharp 2320 – 2270 cm

—H : Sharp 2320 – 2270 cm

-1

-1

P

P

H

H

2

2

bending : 1090 – 1075 and 840 - 810 cm

bending : 1090 – 1075 and 840 - 810 cm

-1

-1

P

P

H bending : 990 - 886 cm

H bending : 990 - 886 cm

-1

-1

Phosphine Oxide : R

Phosphine Oxide : R

3

3

P=O

P=O

P

P

=O very strong : 1210 - 1140 cm

=O very strong : 1210 - 1140 cm

-1

-1

Phosphate Esters : (OR)

Phosphate Esters : (OR)

3

3

P=O

P=O

P

P

=O very strong : 1300 - 1240 cm

=O very strong : 1300 - 1240 cm

-1

-1

P

P

-O very strong : 1088 – 920 cm

-O very strong : 1088 – 920 cm

-1

-1

P

P

-O : 845 - 725 cm

-O : 845 - 725 cm

-1

-1

Silicon

Silicon

IR-Organometallic

IR-Organometallic

Index

Si-H :

Si-H :

2200 cm

2200 cm

-1

-1

(Stretch)

(Stretch)

950 – 800 cm

950 – 800 cm

-1

-1

(bend)

(bend)

Si-O-H :

Si-O-H :

OH: 3700 – 3200 cm

OH: 3700 – 3200 cm

-1

-1

(Stretch)

(Stretch)

Si-O : 830 – 1110 cm

Si-O : 830 – 1110 cm

-1

-1