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THE CHEMISTRY OF AUTUMN COLORS

THE CHEMISTRY OF AUTUMN COLORS. Martin Drastík. Why would I like to speak about this topic? Sad but beautiful. Pigments. C hlorophyll – green C arotene – orange A nthocyanin – red, purple. C hlorophyll. Molecule is large (C 55 H 70 MgN 4 O 6 ) Porphyrin ring + magnesium

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THE CHEMISTRY OF AUTUMN COLORS

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  1. THE CHEMISTRY OF AUTUMN COLORS Martin Drastík

  2. Why would I like to speak about this topic? • Sad but beautiful

  3. Pigments • Chlorophyll – green • Carotene – orange • Anthocyanin – red,purple

  4. Chlorophyll • Molecule is large (C55H70MgN4O6) • Porphyrin ring + magnesium • Situated in leafs – organelles

  5. Chlorophyll • Chloroplasts • Not soluble in the aqueous solution of cells • Photosynthesis of sugars and starches

  6. Chlorophyll • Why do the leaves seem to be green? • Absorption spectrum

  7. Chlorophyll • Not a very stable compound; decomposed by bright sunlight • Continuously synthesized in leaves (requires sunlight and  temperatures) until autumn

  8. Carotene • Large molecule (C40H36) • Situated in the chloroplasts • Function: accessory absorber - energy transferred to chlorophyll

  9. Carotene • Absorption spectrum • Much more stable than chlorophyll • Carotene persists in leafs even when chlorophyll has disappeared

  10. Anthocyanin • Various structures – diff. is „B“ benzenoid ring • Disolved in the aqueous solu- tion of cells

  11. Anthocyanin • Absorption spectrum • Color is sensitive to the pH of the cell sap

  12. Anthocyanin • If the sap is acidic – bright red • If the sap is neutral – purple • If the sap is alkaline– orange alkaline; neutral; acidic

  13. Anthocyanin • 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

  14. Conclusion • Summer: • Autumn: stop of producing chlorophyll, storing energy in fruit and nuts changing color of leaves

  15. Thank you for your attention • The biggest source of information: Prof. Shakhashiri, University of Wisconsin-Madison Chemistry: Chemical of the Week • Pictures – internet

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