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DETERMINACI N DE ESTRUCTURAS ORG NICAS(ORGANIC SPECTROSCOPY)

ESPECTROSCOPA INFRARROJA

Hermenegildo Garca GmezHermenegildo Garca GmezDepartamento de QumicaDepartamento de Qumica

Instituto de Tecnologa QumicaInstituto de Tecnologa Qumica

Universidad Politcnica de ValenciaUniversidad Politcnica de Valencia46022 Valencia46022 Valencia

EE--mail:mail: hgarcia@qim.upv.eshgarcia@qim.upv.es

Telephone: +34 96 387 7807 or ext. 78572/73441Telephone: +34 96 387 7807 or ext. 78572/73441Fax: + 34 96 387 7809Fax: + 34 96 387 7809

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ESPECTROSCOPA DE INFRARROJOS

- Niveles electrnicos- UV-Visible: transiciones de

electrones entre dos estados

electrnicos

- Niveles vibracionales dentrode un nivel electrnico

- Diferencia de energa muchomenor

- Hace falta onda con frecuenciams pequea

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FUNDAMENTAL VIBRATION MODES

- A molecule contains two or more atoms and several bonds- The position of each atom is indicated by three coordinates- If we have n atoms we need 3n coordinates- Three degrees of freedom are wasted in translation

- Degree of freedom for vibration: 3n-3

CzCy

Cx

C

BzB

yB

x

B

Az

AyA

x

A

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VIBRATION OF SINGLE BONDS AND GROUPS

1- A molecule may contain many atoms and bonds. In reality a vibration isnot located in a single bond or group of atoms, but

2- In a simplified model, the rest of the molecule can be considered ashaving infinite mass.

3- The conclusion of the previous point is that each covalent bond hasspecific absorptions irrespective of the rest of the molecule.

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TI POS DE VI BRACIONES

- Stretching: change in the atomic distance- Bending: changes in the bond angles

H2O

CO

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CH2

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1- All the covalent bond has a typical wavenumber irrespective of theconcentration at which the IR spectrum is recorded.

2- Except when there is a hydrogen bond

Hydrogen bonded to an electronegative element

|

HNR

HOR

HCl

HF

3- The intensity of the hydrogen bond depends on the difference of electronegativity

on other inductive effects

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FOTMETRO

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ALCANOS

A: CH2and CH3symmetric and asymmetric stretching

B: CH2bending. Sharp peak at 1370 cm-1corresponds to CH3;

C: rocket band

ALQUENOS

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ALQUENOS

A: CH2and CH3asymmetric and symmetric stretching

B: CH2bending. With several CH3at 1370 cm-1

A: C-H stretching. Above 3000 cm-1C-H (sp2); below 3000 cm-1C-H (sp3)

B: CH2=CH stretching vibration. Not visible in symmetric alkenes

C: CH2bending + CH3

D: CH2=C bending

ALQUINO

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ALQUINO

H IDROCARBURO AROMTICO (ORTOXIL ENO)

ALCOHOLES

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ALCOHOLES

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TER

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EJEMPLO DE I NTERACCIN POR PUENTES DE H IDRGENO

COMPUESTOS CARBONLICOS

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COMPUESTOS CARBONLICOS

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PROBLEMAS PROPUESTOS

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PPRROOBBLLEEMMAA11

PPRROOBBLLEEMMAA22

PPRROOBBLLEEMMAA33

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PP 33

PPRROOBBLLEEMMAA44

PPRROOBBLLEEMMAA55

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PP 55

PPRROOBBLLEEMMAA66

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PPRROOBBLLEEMMAA88

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PPRROOBBLLEEMMAA1100

PPRROOBBLLEEMMAA1111

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PPRROOBBLLEEMMAA1122

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PPRROOBBLLEEMMAA1177

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PPRROOBBLLEEMMAA1188

PPRROOBBLLEEMMAA1199

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PPRROOBBLLEEMMAA2200

PPRROOBBLLEEMMAA2211

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PPRROOBBLLEEMMAA2222

PPRROOBBLLEEMMAA2233

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PPRROOBBLLEEMMAA2244

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