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The Chemistry Behind Autumn Colors: A Fascinating Transformation

Delve into the intriguing world of autumn colors as we explore the chemistry of pigments like chlorophyll, carotene, and anthocyanin. Discover how these compounds, with their unique properties and functions, give rise to the vibrant hues of fall foliage. From the composition of chlorophyll to the color-changing process in leaves, this topic offers a blend of science and artistry that captivates the senses. Join us on this colorful journey to understand the magic of nature's seasonal palette.

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The Chemistry Behind Autumn Colors: A Fascinating Transformation

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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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