The Beer-Bouger-Lambert Law and max The Beer’s law: At a given the proportion of light absorbed...

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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 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

Transcript of The Beer-Bouger-Lambert Law and max The Beer’s law: At a given the proportion of light absorbed...

Page 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.

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.

I0 is the intensity of incident lightI is the intensity of transmitted lightk is the absorption coefficientl is the path length through the sample is molar extinction coefficient or molar absorptivityc is the concentration in mol/LSo k ≈ 2.303 c

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Changes of Absorption Maxima

Page 3: 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.

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

Page 4: 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.

= resonance energy; it becomes 0 if EA is big

S = overlap integral that typically is about 0.2

E+- = (EA +- )/(1+-S)

Linear Combination of AOs (LCAO)

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

Page 6: 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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Penta-1,3-diene in heptane

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Absorption of alkenes

Page 9: 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.

Absorption of alkenes

Page 10: 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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Absorption of isolated chromophores