ir spectrascopy for inorganic xompounds

8/9/2019 IR Spectrascopy for Inorganic Xompounds

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IR spectrascopy for inorganic xompounds

Infrared: Interpretation

Table of Contents

. 1. Introduction

. 2. The Orgin of Infrared Peak Positions, Intensities, and Widths

. 2.1. Peak Positions

. 2.2. The Origin of Peak Intensities

. 2.3. The Orgins of Peak Widths

. 2.. The Origin of !roup "re#uencies

. 3. $pectral Interpretation b% &pplication of !roup "re#uencies

. 3.1. Organic Co'pounds

. 3.1.1. "unctional !roups Containing the C(O )ond

. 3.1.2. Organic *itrogen Co'pounds

. 3.1.3. Organic Co'pounds Containing +alogens

. 3.2. Inorganic Co'pounds

. . Identification

. . -eferences

. . Outside /inks

Infrared spectroscop% is the stud% of the interaction of infrared light 0ith 'atter. The funda'ental 'easure'ent

obtained in infrared spectroscop% is an infrared spectru', 0hich is a plot of 'easured infrared intensit% ersus

0aelength or fre#uenc% of light.

Introduction

In infrared spectroscop%, units called 0aenu'bers are nor'all% used to denote different t%pes of light. The

fre#uenc%, 0aelength, and 0aenu'ber are related to each other ia the follo0ing e#uation1:

1

These e#uations sho0 that light 0aes 'a% be described b% their fre#uenc%, 0aelength or 0aenu'ber. +ere,

0e t%picall% refer to light 0aes b% their 0aenu'ber, ho0eer it 0ill be 'ore conenient to refer to a light

0ae4s fre#uenc% or 0aelength. The 0aenu'ber of seeral different t%pes of light are sho0n in table 1.
http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Introductionhttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#The_Orgin_of_Infrared_Peak_Positions.2C_Intensities.2C_and_Widthshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Peak_Positionshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#The_Origin_of_Peak_Intensitieshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#The_Orgins_of_Peak_Widthshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#The_Origin_of_Group_Frequencieshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Spectral_Interpretation_by_Application_of_Group_Frequencieshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Organic_Compoundshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Functional_Groups_Containing_the_C-O_Bondhttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Organic_Nitrogen_Compoundshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Organic_Compounds_Containing_Halogenshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Inorganic_Compoundshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Identificationhttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Referenceshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Outside_Linkshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#The_Orgin_of_Infrared_Peak_Positions.2C_Intensities.2C_and_Widthshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Peak_Positionshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#The_Origin_of_Peak_Intensitieshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#The_Orgins_of_Peak_Widthshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#The_Origin_of_Group_Frequencieshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Spectral_Interpretation_by_Application_of_Group_Frequencieshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Organic_Compoundshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Functional_Groups_Containing_the_C-O_Bondhttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Organic_Nitrogen_Compoundshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Organic_Compounds_Containing_Halogenshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Inorganic_Compoundshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Identificationhttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Referenceshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Outside_Linkshttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Interpretation#Introduction


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Table 1. The 5lectro'agnetic spectru' sho0ing the 0aenu'ber of seeral different t%pes of light.

When a 'olecule absorbs infrared radiation, its che'ical bonds ibrate. The bonds can stretch, contract, and

bend. This is 0h% infrared spectroscop% is a t%pe of ibrational spectroscop%. "ortunatel%, the co'ple6

ibrational 'otion of a 'olecule can be broken do0n into a nu'ber of constituent ibrations called nor'al

'odes. "or e6a'ple, 0hen a guitar string is plucked, the string ibrates at its nor'al 'ode fre#uenc%.7olecules, like guitar strings, ibrate at specfic fre#uencies so different 'olecules ibrate at different

fre#uencies because their structures are different. This is 0h% 'olecules can be distinguished using infrared

spectroscop%. The first necessar% condition for a 'olecule to absorb infrared light is that the 'olecule 'ust

hae a ibration during 0hich the change in dipole 'o'ent 0ith respect to distance is non(8ero. This condition

can be su''ari8ed in e#uation2 for' as follo0s:

2

9ibrations that satisf% this e#uation are said to be infrared actie. The +(Cl stretch of h%drogen chloride and theas%''etric stretch of CO2are e6a'ples of infrared actie ibrations. Infrared actie ibrations cause the bands

seen in an infrared spectru'.

The second necessar% condition for infrared absorbance is that the energ% of the light i'pinging on a 'olecule

'ust e#ual a ibrational energ% leel difference 0ithin the 'olecule. This condition can be su''ari8ed in

e#uation3 for' as follo0s:

3

If the energ% of a photon does not 'eet the criterion in this e#uation, it 0ill be trans'itted b% the sa'ple and if

the photon energ% satisfies this e#uation, that photon 0ill be absorbed b% the 'olecule.$ee Infrared: Theor%

for 'ore detail

&s an% other anal%tical techni#ues, infrared spectroscop% 0orks 0ell on so'e sa'ples, and poorl% on others. It

is i'portant to kno0 the strengths and 0eaknesses of infrared spectroscop% so it can be used in the proper 0a%.$o'e adantages and disadantages of infrared spectroscop% are listed in table 2.

&dantages isadantages

$olids, /i#uids, gases, se'i(solids, po0ders and

pol%'ers are all anal%8ed

&to's or 'onato'ic ions do not hae infrared spectra
http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Theoryhttp://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Theory


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The peak positions, intensities, 0idths, and shapes

all proide useful infor'ation

"ast and eas% techni#ue

$ensitie techni#ue 7icrogra's of 'aterials can

be detected routinel%

Ine6pensie

+o'onuclear diato'ic 'olecules do not posses infrared

spectra

Co'ple6 'i6ture and a#ueous solutions are difficult to

anal%8e using infrared spectroscop%

Table 2. The &dantage and isadantage of Infrared $pectroscop%

The Orgin of Infrared Peak Positions, Intensities, and Widths

Peak Positions

The e#uation gies the fre#uenc% of light that a 'olecule 0ill absorb, and gies the fre#uenc% of ibration of

the nor'al 'ode e6cited b% that light.

Onl% t0o ariables in e#uation are a che'ical bond4s force constant and reduced 'ass. +ere, the reduced

'ass refers to 7172;71>c'(1.

Table . &n 56a'ple of an electronic 5ffect

)ond C(+ $tretch in c'(1

C(+ =3>>>

+(C@O =2A>

When a h%drogen is attached to a carbon 0ith a C@O bond, the C(+ stretch band position decrease to =2A>c' (

1. These t0o C(+ bonds hae the sa'e reduced 'ass but different force constants. The o6%gen in the second

'olecule pulls electron densit% a0a% fro' the C(+ bond so it 'akes 0eaken and reduce the C(+ force

constant. This cause the C(+ stretching ibration to be reduced b% =2>c'(1.


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The Origin of Peak Intensities

The different ibrations of the different functional groups in the 'olecule gie rise to bands of differing

intensit%. This is because x is different for each of these ibrations. "or e6a'ple, the 'ost intense bandin the spectru' of octane sho0n in "igure 3 is at 2BA1, 2?3 c' (1and is due to stretching of the C(+ bond. One

of the 0eaker bands in the spectru' of octane is at A2c' (1, and it is due to long(chain 'eth%l rock of the

carbon(carbon bonds in octane. The change in dipole 'o'ent 0ith respect to distance for the C(+ stretching is

greater than that for the C(C rock ibration, 0hich is 0h% the C(+ stretching band is the 'ore intense than C(C

rock ibration.

&nother factor that deter'ines the peak intensit% in infrared spectra is the concentration of 'olecules in the

sa'ple. The e#uation that relates concentration to absorbance is )eer4s la0,

The absorptiit% is the proportionalit% constant bet0een concentration and absorbance, and is dependent on

/x)2. The absorptiit% is an absolute 'easure of infrared absorbance intensit% for a specific 'olecule at a

specific 0aenu'ber. "or pure sa'ple, concentation is at its 'a6i'u', and the peak intensities are true

representations of the alues of /x for different ibrations. +o0eer, in a 'i6ture, t0o peaks 'a% hae

different intensities because there are 'olecules present in different concentration.

The Orgins of Peak WidthsIn general, the 0idth of infrared bands for solid and li#uid sa'ples is deter'ined b% the nu'ber of che'ical

eniron'ents 0hich is related to the strength of inter'olecular interactions such as h%drogen bonding. "igure

1. sho0s h%drogen bond in 0ater 'olecules and these 0ater 'olecules are in different che'ical eniron'ents.

)ecause the nu'ber and strength of h%drogen bonds differs 0ith che'ical eniron'ent, the force constant

aries and the 0aenu'ber differs at 0hich these 'olecules absorb infrared light.

"igure 1. +%drogen )onding in 0ater 'olecules

In an% sa'ple 0here h%drogen bonding occurs, the nu'ber and strength of inter'olecular interactions aries

greatl% 0ithin the sa'ple, causing the bands in these sa'ples to be particularl% broad. This is illustrated in the

spectra of ethanol"igA and he6anoic acid"ig11. When inter'olecular interactions are 0eak, the nu'ber of

che'ical eniron'ents is s'all, and narro0 infrared bands are obsered.

The Origin of !roup "re#uencies


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&n i'portant obseration 'ade b% earl% researchers is that 'an% functional group absorb infrared radiation at

about the sa'e 0aenu'ber, regardless of the structure of the rest of the 'olecule. "or e6a'ple, C(+

stretching ibrations usuall% appear bet0een 32>> and 2?>>c' (1 and carbon%lC@O stretching ibrations

usuall% appear bet0een 1?>> and 1>>c'(1. This 'akes these bands diagnostic 'arkers for the presence of a

functional group in a sa'ple. These t%pes of infrared bands are called group fre#uencies because the% tell us

about the presence or absence of specific functional groups in a sa'ple.

"igure 2. !roup fre#uenc% and fingerprint regions of the 'id(infrared spectru'

The region of the infrared spectru' fro' 12>> to A>> c'(1 is called the fingerprint region. This region is

notable for the large nu'ber of infrared bands that are found there. 7an% different ibrations, including C(O,C(C and C(* single bond stretches, C(+ bending ibrations, and so'e bands due to ben8ene rings are found in

this region. The fingerprint region is often the 'ost co'ple6 and confusing region to interpret, and is usuall%

the last section of a spectru' to be interpreted. +o0eer, the utilit% of the fingerprint region is that the 'an%

bands there proide a fingerprint for a 'olecule.

$pectral Interpretation b% &pplication of !roup "re#uencies

Organic Co'pounds

One of the 'ost co''on application of infrared spectroscop% is to the identification of organic co'pounds.The 'aor classes of organic 'olecules are sho0n in this categor% and also linked on the botto' page for the

nu'ber of collections of spectral infor'ation regarding organic 'olecules.

+%drocarbons

+%drocarbons co'pounds contain onl% C(+ and C(C bonds, but there is plent% of infor'ation to be obtained

fro' the infrared spectra arising fro' C(+ stretching and C(+ bending.

In alkanes, 0hich hae er% fe0 bands, each band in the spectru' can be assigned:

CD+ stretch fro' 3>>>D2?> c'(1 CD+ bend or scissoring fro' 1A>(1> c'(1

CD+ rock, 'eth%l fro' 13A>(13> c'(1

CD+ rock, 'eth%l, seen onl% in long chain alkanes, fro' A2(A2> c'(1
http://chemwiki.ucdavis.edu/@api/deki/files/9606/group_frequency1_(1).gif


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"igure 3. sho0s the I- spectru' of octane. $ince 'ost organic co'pounds hae these features, these C(+

ibrations are usuall% not noted 0hen interpreting a routine I- spectru'. *ote that the change in dipole

'o'ent 0ith respect to distance for the C(+ stretching is greater than that for others sho0n, 0hich is 0h% the

C(+ stretch band is the 'ore intense.

"igure 3. Infrared $pectru' of Octane

In alkenes co'pounds, each band in the spectru' can be assigned:

C@C stretch fro' 1?>(1> c'(1

@CD+ stretch fro' 31>>(3>>> c'(1

@CD+ bend fro' 1>>>(> c'(1

"igure . sho0s the I- spectru' of 1(octene. &s alkanes co'pounds, these bands are not specific and are

generall% not noted because the% are present in al'ost all organic 'olecules.

"igure . Infrared $pectru' of 1(Octene

In alk%nes, each band in the spectru' can be assigned:

DCECD stretch fro' 22>(21>> c'(1 DCECD+: CD+ stretch fro' 333>(32A> c'(1

DCECD+: CD+ bend fro' A>>(1> c'(1

The spectru' of 1(he6%ne, a ter'inal alk%ne, is sho0n belo0.


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"igure . Infrared $pectru' of 1(+e6%ne

In aro'atic co'pounds, each band in the spectru' can be assigned:

CD+ stretch fro' 31>>(3>>> c'(1

oertones, 0eak, fro' 2>>>(1 c'(1

CDC stretch in(ring fro' 1>>(1? c'(1

CDC stretch in(ring fro' 1>>(1>> c'(1

CD+ FoopF fro' B>>(A c'(1

*ote that this is at slightl% higher fre#uenc% than is the DCD+ stretch in alkanes. This is a er% useful tool for

interpreting I- spectra. Onl% alkenes and aro'atics sho0 a CD+ stretch slightl% higher than 3>>> c' (1.

"igure . sho0s the spectru' of toluene.

"igure . Infrared $pectru' of Toluene

"unctional !roups Containing the C(O )ond

&lcohols hae I- absorptions associated 0ith both the O(+ and the C(O stretching ibrations.

OD+ stretch, h%drogen bonded 3>>(32>> c'(1

CDO stretch 12>(1>> c'(1s

"igure A. sho0s the spectru' of ethanol. *ote the er% broad, strong band of the OD+ stretch.


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"igure A. Infrared $pectru' of 5thanol

The carbon%l stretching ibration band C@O of saturated aliphatic ketones appears:

C@O stretch ( aliphatic ketones 1A1 c' (1

( E, E(unsaturated ketones 1?(1 c'(1

"igure ?. sho0s the spectru' of 2(butanone. This is a saturated ketone, and the C@O band appears at 1A1.

"igure ?. Infrared $pectru' of 2()utanone

If a co'pound is suspected to be an aldeh%de, a peak al0a%s appears around 2A2> c' (10hich often appears as

a shoulder(t%pe peak ust to the right of the alk%l CD+ stretches.

+DC@O stretch 2?3>(2B c'(1

C@O stretch:

o aliphatic aldeh%des 1A>(1A2> c'(1

o alpha, beta(unsaturated aldeh%des 1A1>(1? c'(1

"igure B. sho0s the spectru' of but%raldeh%de.


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"igure B. Infrared $pectru' of )ut%raldeh%de

The carbon%l stretch C@O of esters appears:

C@O stretch

o aliphatic fro' 1A>(1A3 c'(1

o E, E(unsaturated fro' 1A3>(1A1 c'(1

CDO stretch fro' 13>>(1>>> c'(1

"igure 1>. sho0s the spectru' of eth%l ben8oate.

"igure 1>. Infrared $pectru' of 5th%l ben8oate

The carbon%l stretch C@O of a carbo6%lic acid appears as an intense band fro' 1A>(1B> c' (1. The e6act

position of this broad band depends on 0hether the carbo6%lic acid is saturated or unsaturated, di'eri8ed, or

has internal h%drogen bonding.

OD+ stretch fro' 33>>(2>> c'(1

C@O stretch fro' 1A>(1B> c'(1

CDO stretch fro' 132>(121> c'(1

OD+ bend fro' 1>(13B and B>(B1> c'(1

"igure 11. sho0s the spectru' of he6anoic acid.


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"igure 11. Infrared $pectru' of +e6anoic acid

Organic *itrogen Co'pounds

*DO as%''etric stretch fro' 1>(1A c'(1

*DO s%''etric stretch fro' 13>(12B> c'(1

"igure 12. Infrared $pectru' of *ito'ethane

Organic Co'pounds Containing +alogens

&lk%l halides are co'pounds that hae a CDG bond, 0here G is a halogen: bro'ine, chlorine, fluorene, or

iodine.

CD+ 0ag (C+2G fro' 13>>(11> c'(1

CDG stretches general fro' ?>(1 c'(1

o CDCl stretch ?>(> c'(1

o CD)r stretch B>(1 c'(1

The spectru' of 1(chloro(2('eth%lpropane are sho0n belo0.


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"igure 13. Infrared $pectru' of 1(chloro(2('eth%lpropane

"or 'ore Infrared spectra $pectral database of organic 'olecules is introduced to use free database. &lso, the

infrared spectroscop% correlation tableis linked on botto' of page to find other assigned I- peaks.

Inorganic Co'pounds

!enerall%, the infrared bands for inorganic 'aterials are broader, fe0er in nu'ber and appear at lo0er

0aenu'bers than those obsered for organic 'aterials. If an inorganic co'pound for's coalent bonds

0ithin an ion, it can produce a characteristic infrared spectru'.

7ain infrared bands of so'e co''on inorganic ions:

CO32( 1>(11>, ??>(?>>c'(1

$O2(113>(1>?>, ?>(1>c'(1

*O3( 11>(13>, ?>(?>>c'(1

PO3(11>>(B>c'(1

$iO2(11>>(B>>c'(1

*+3>, 1?(13B>c'(1

7nO( B2>(?B>, ?>(?>c'(1

iato'ic 'olecules produce one ibration along the che'ical bond. 7onato'ic ligand, 0here 'etal s

coordinate 0ith ato's such as halogens, +, * or O, produce characteristic bands. These bands are su''ari8edin belo0.

Chracteristic infrared bands of diato'ic inorganic 'olecules: 7'etal, Ghalogen

7(+ stretching 22>(1A>>c'(1

7(+ bending ?>>(>>c'(1

7(G stretching A>(1>>c'(1

7@O stretching 1>1>(?>c'(1

7@* stretching 1>2>(?Ac'(1

The nor'al 'odes of ibration of linear and bent triato'ic 'olecules are illustrated and so'e co''on linearand bent triato'ic 'olecules are sho0n belo0. *ote that so'e 'olecules sho0 t0o bands for ?1because of

"er'i resonance.

Characteristic infrared bandsc'(1 of triato'ic inorganic 'olecules:
http://riodb01.ibase.aist.go.jp/sdbs/http://en.wikipedia.org/wiki/Infrared_spectroscopy_correlation_tablehttp://en.wikipedia.org/wiki/Fermi_resonancehttp://riodb01.ibase.aist.go.jp/sdbs/http://en.wikipedia.org/wiki/Infrared_spectroscopy_correlation_tablehttp://en.wikipedia.org/wiki/Fermi_resonance


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/inear 7olecules OCO +C* *C$(ClC* 7gCl2

13??, 12? 3311 2>3 A1, A? 32A

A A12 ?, A1 3?> 2B

23B 2>B A? 221B ?2

)ent 7olecules +2O O3$nCl 2

3A 113 3

1B A1 12>

3A 1>?B 33

Identification

There are a fe0 general rules that can be used 0hen using a 'id(infraredspectru' for the deter'ination of a 'olecular structure. The follo0ing is a

suggested strateg% for spectru' interpretation:2

1. /ook first at the high( 0aenu'ber end of the spectru'H1>>c'(1

and concentrate initiall% on the 'aor bands

2. "or each band, 4short(list4 the possibilities b% using a correlation table

3. se the lo0er(0aenu'ber end of the spectru' for the confir'ation or

elaboration of possible structural ele'ents

. o not e6pect to be able to assign eer% band in the spectru'

. Jeep 4cross(checking4 0hereer possible.

. 56ploit negatie eidence as 0ell as positie eidenceA. )and intensities should be treated 0ith so'e caution. nder certain circu'stances, the% 'a% ar%

considerabl% for the sa'e group

?. Take care 0hen using s'all 0aenu'ber changes. If in solution, so'e bands are er% 4solent(sensitie4

B. o not forget to subtract sloent bands if possible

Infrared spectroscop% is used to anal%8e a 0ide ariet% of sa'ples, but it cannot sole eer% che'ical anal%sis

proble'. When used in conunction 0ith other 'ethods such as 'ass spectroscop%, nuclear 'agnetic

resonance, and ele'ental anal%sis, infrared spectroscop% usuall% 'akes possible the positie identification of a

sa'ple.

ir spectrascopy for inorganic xompounds

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