THE CHEMISTRY OF
AUTUMN COLORS
Martin Drastík
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Why would I like to speak about this topic?
Sad but beautiful
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Pigments
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Chlorophyll – green
Carotene – orange
Anthocyanin – red, purple
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Chlorophyll
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Molecule is large
(C55H70MgN4O6)
Porphyrin ring +
magnesium
Situated in leafs –
organelles
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Chlorophyll
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Chloroplasts
Not soluble in
the aqueous
solution of cells
Photosynthesis
of sugars and
starches
 chlorophyll
CO2  H 2O light

 O2  carbohydra tes
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Chlorophyll
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Why do the leaves seem to be green?
Absorption
spectrum
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Chlorophyll
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Not a very stable
compound;
decomposed
by bright sunlight
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Continuously synthesized in leaves (requires
sunlight and  temperatures) until autumn
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Carotene
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H3C
Large molecule (C40H36)
CH3
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CH3
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1
6
3
5
4
11
10
13
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15
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14'
15'
12'
13'
CH3
CH3
5'
3'
6'
2'
20
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8
18'
CH3
19
7
2
4'
H3C
20'
10'
11'
8'
9'
7'
CH3
19'
1'
H3C
16'
CH3
17'
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Situated in the chloroplasts
Function: accessory absorber - energy
transferred to chlorophyll
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Carotene
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Absorption spectrum
Much more stable than
chlorophyll
Carotene persists in
leafs even when
chlorophyll has
disappeared
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Anthocyanin
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Various structures –
diff. is „B“ benzenoid
ring
Disolved in the
aqueous solution of cells
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Anthocyanin
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Absorption
spectrum
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Color is sensitive to the pH of the cell sap
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Anthocyanin
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If the sap is acidic – bright red
If the sap is neutral – purple
If the sap is alkaline – orange
alkaline;
neutral; acidic
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Anthocyanin
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Formed by a reaction between sugars and
certain proteins in cell. Occurs when
concentration of sugar in the sap is high
enough.
Requires light
Red side insolate
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Conclusion
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Summer:
 chlorophyll
CO2  H 2O light

 O2  carbohydra tes
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Autumn: stop of producing chlorophyll,
storing energy in fruit
and nuts
changing color of leaves
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Thank you for your attention
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The biggest source of information:
Prof. Shakhashiri, University of WisconsinMadison Chemistry: Chemical of the Week
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Pictures – internet
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