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The Beer-Bouger-Lambert Law and  max The Beer’s law: At a given the proportion of light absorbed by a transparent medium is independent of the intensity.

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Presentation on theme: "The Beer-Bouger-Lambert Law and  max The Beer’s law: At a given the proportion of light absorbed by a transparent medium is independent of the intensity."— Presentation transcript:

1 The Beer-Bouger-Lambert Law and  max The Beer’s law: At a given the proportion of light absorbed by a transparent medium is independent of the intensity of the incident light and is proportional to the number of absorbing molecules through which the light passes. I 0 is the intensity of incident light I is the intensity of transmitted light k is the absorption coefficient l is the path length through the sample  is molar extinction coefficient or molar absorptivity c is the concentration in mol/L So k ≈  c

2 Changes of Absorption Maxima

3 In-phase overlap region of AOs = bonding MO Out-of-phase overlap region of AOs (nodal plane) = antibonding MO AOs being combined must have similar energy and the same symmetry with respect to the internuclear axis

4  = resonance energy; it becomes 0 if  E A is big S = overlap integral that typically is about 0.2 E +- = (E A +-  )/(1+-S) Linear Combination of AOs (LCAO)

5 g = even (gerade) and u = odd (ungerade) with regard to inverion

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7 Penta-1,3-diene in heptane

8 Absorption of alkenes

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11 Absorption of isolated chromophores


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