DETERMINACIÓN DE ESTRUCTURAS ORGÁNICAS(ORGANIC SPECTROSCOPY)

UV/VIS SPECTROSCOPY

Hermenegildo García GómezHermenegildo García GómezDepartamento de QuímicaDepartamento de Química

Instituto de Tecnología QuímicaInstituto de Tecnología QuímicaUniversidad Politécnica de ValenciaUniversidad Politécnica de Valencia

46022 Valencia46022 Valencia

EE--mail: mail: hgarcia@qim.upv.eshgarcia@qim.upv.esTelephone: +34 96 387 7807 or ext. 78572/73441Telephone: +34 96 387 7807 or ext. 78572/73441

Fax: + 34 96 387 7809Fax: + 34 96 387 7809

UV/VisA typical UV/Vis Basic equation of all spectroscopics

chhc

hE υλ

υ ===∆

E∆ Difference in energy of thequantized levels of a compound

chhc

h υλ

υ == Wave energy

Electromagnetic spectrum

Orbitals π y π*

Diagram of electronic levels

I0I

b

Sample0II

T =

=

II

A 0

10log

kcbA =

Transmittance

Absorbance

Lambert-Beer Law

c = concentration K = molar absorptivity

Table 1. Sumary of electronic transitions

DefinitionsCHOMOPHORE. A covalently unsaturated group responsible for electronic absortion (for example, C=C, C=O, and NO2).

AUXOCHROME. A saturated group with nonbonded electrons which, when attached to a chromophore, alters both the wavelength and the intensity of the absorption

BATHOCHROMIC SHIFT. The shift of absorption to a longer wavelength due to substitution or solvent effect (a red shift).

HYPSOCHROMIC SHIFT. The shift of absorption to a shorter wavelength due to substitution or solvent effect (a blue shift).

HYPERCHROMIC EFFECT. An increase in absorption intensity.

HYPOCHROMIC EFFECT. A decrease in absorption intensity.

Solvents

Conjugated dienes

Example Problem

Conjugated polyenes

Examples

Problems

Problems

1.-

2.-

3.-

4.-

5.-