The chemistry of autumn leaf color changes is due to the breakdown of chlorophyll and the revealing of carotenoid pigments. Chlorophyll produces the green color in leaves and is responsible for photosynthesis. In autumn, as the sunlight decreases, chlorophyll breaks down which allows the yellow, orange, and brown carotenoid pigments to shine through, changing the color of the leaves. The red anthocyanin pigments also become visible. This chemical process is what makes the season of fall so visually stunning each year.

1. The Chemistry of the Fall
By: Ali Davidson

2. Summary
• Autumn is a beautiful time of year for many reasons. The air
begins to feel a bit crisper, hot apple cider starts to sound good
again, and the leaves of the trees begin to change into many
gorgeous colors.
• However, there are very specific reasons due to the chemistry in
the leaves that causes this change.

3. Summary, continued
• Chlorophyll in the leaves begins to
receive less and less sunlight, and
pigments that are not usually seen
begin to come out due to the lack of
proper sunlight for the green color
to show through (Shakhashiri 1).
• The carotenoids, which produce the
“fall colors” such as yellow, orange,
and brown in leaves, begin to show
through more and more, causing the
leaves to change colors (Tackett 1).

4. Chemistry: The three pigments in leaves
Chlorophyll
• Main component of leaves
• Two types:
• C55H72MgN4O5 for chlorophyll a
• C55H70MgN4O6 for chlorophyll b
• Produce green coloring in leaves
• Is involved in photosynthesis, which
provides food for the plant
• (Lear 8-9)
Carotenoids
• Produce brown, orange, and
yellow colors
• Most perceived “fall colors” come
from carotenoids
• (Lear 8-9)
Anthocyanin
• Produce blue and red coloring in
plants
• (Lear 8-9)

5. Chemistry: Photosynthesis
• Shakhashiri labels photosynthesis is an endothermic reaction, which we
learned as a reaction that gains energy.
• An equation to model photosynthesis could be represented one of two
ways:
• Shakhashiri uses the equation: xCO2 + xH2O light/chlorophyll Cx (H2O)x +
xO2
• Lear uses the equation: 6CO2 + 7H20 + Sunlight Chlorophyll C6H12O6 + 6O2
+ H2O. Lear also states that “chlorophyll can be regarded as a catalyst” (8). We
learned that a catalyst helps to boost the reaction, without actually getting
involved.
• Photosynthesis is how leaves produce sugars to sustain themselves. They
use the sunlight and chlorophyll to make sugar (C6H12O6).

6. Chemistry: Changes in the Fall
• In the fall, trees begin to signal to their leaves to cease
production due to the changing weather. Without the necessary
sunlight and warmth for photosynthesis, the leaves can no longer
sustain themselves, so they have to decompose for the winter.
• The proteins used in photosynthesis break into amino acids, and
shut down for the winter.
• When this occurs, the chlorophyll goes through a decomposition
reaction. All of the pigments go through decomposition, but the
chlorophyll happens to be the fastest, which is why we can see
the beautiful yellow, orange, and brown from carotenoids, as well
as the bright red from the anthocyanin (Shakhashiri 2).

7. Implications
• The chemistry of autumn colors matters to us
because we can see them everywhere in
Nashville from sometime in September to late
November.
• Knowing the chemistry of these changes allows
us to be able to acknowledge the science
behind a beautiful season.
• Next time you see changing leaves, think of
chlorophyll and its decomposition.

8. Works Cited
Lear, Brad. "Autumn Leaves." Chemmatters: 7-10. Print.
National Forest Service. USDA Forest Service, 7 July 2011. Web. 3 Apr.
2014. <http://www.na.fs.fed.us/fhp/pubs/leaves/leaves.shtm>.
PBS News Hour. PBS, 12 Oct. 2011. Web. 3 Apr. 2014.
<http://www.pbs.org/newshour/rundown/why-do-leaves-change-
color/>.
Shakhashiri. "The Chemistry of Autumn Colors." Scifun. Wics.edu,
23 Jan. 2008. Web. 3 Apr. 2014.
<http://scifun.chem.wisc.edu/chemweek/fallcolr/fallcolr.ht ml>.