Autumnal coloring of leaves

The bright colors of flowers and the varied hues of autumn leaves have always been a cause for delight, but it was nor until the twentieth century that chemists understood how these colors arise from the presence of organic compounds with common structural features. They discovered how small differences in the structures of the molecules of these compounds can enhance photosynthesis, produce important vitamins, and attract pollinating bees. They now know how the shapes of molecules and the orbitals occupied by their electrons explain the properties of these compounds and even the processes taking place in our eyes that allow us to see them. 

Many of the beautiful colors of butterflies wings, autumn leaves, and flowers are due to the presence of flavone derivatives called anthocyanins. When antho-cyanins are hydrolyzed in hydrochloric acid (to remove sugar residues), they produce aromatic oxygen-containing salts. One of these is delphinidin chloride. Explain why delphinidin chloride is aromatic. What is the hybridization of the heterocyclic oxygen in this compound ... 

When green chlorophyll decays, the colors of autumn leaves are revealed. 

In Autumn, leaves turn from green (the color of chlorophyll) to the oranges and reds of carotene... 

The world is composed of molecules. Some are synthetic while many others are products of nature. Molecules That Amaze Us presents the stories behind many of the most famous and infamous molecules that make up our modern world. Examples include the molecule responsible for the spicy heat in chillies (capsaicin), the world s first synthetic painkiller (aspirin), the pigment responsible for the color of autumn leaves (carotene), the explosive in dynamite (nitroglycerine), the antimalarial drug (quinine), the drug known as "speed" (methamphetamine), and many others. 

Maples are characterized by the shape of their leaves, which in most species are broadly palmate with a three- or five-lobed outline, and are arranged in an opposite fashion on their branches. Maples have seasonally deciduous foliage, which is shed in the autumn. The leaves of many species of maples develop beautiful yellow, orange, or red colors in the autumn, prior to shedding for the winter. Maple flowers appear early in the springtime, and consist of non-showy, rather inconspicuous inflorescences. The flowers of some species produce nectar and are insect-pollinated, while other species shed their pollen into the air and are wind-pollinated. Maples have distinctive, winged seeds known as samaras, which are arrar ed in opposite pairs. 

The olive tree has persistent leaves, blooms in the spring, and produces mature fruits in the late autumn or winter. The unripe fruits are green and bitter, while ripe fruits are purple to black in color. The bitterness of the green, unripe fruits can be removed by soaking them in a solution which is alkaline (high pH) or is saturated with salt. Once the bitterness has been removed, green olives are typically pickled in a salt solution for later eating. 

Mountain ashes are fast-growing, alternate-leaved, deciduous trees grown principally for the profuse clusters of white flowers that are followed by brightly colored fruit in autumn. Although rather weak-wooded and very subject to pests and diseases, they are popular as ornamental specimen trees. 

Pokeweed is a tall perennial shrub growing up to 12 ft. This shrub can be found in damp fields, along fences, and wooded areas of southeastern Canada, eastern United States, as well as California and Hawaii. The stalks are reddish. There are small, greenish-white flowers and berries in opposite clusters. The berry is dark purple, almost black in color, and matures late summer to autumn. Pokeweed has been used in tea and as a herbal medicine. In folk medicine, pokeweed as a tincture has been used for arthritis and chronic rheumatism. Taken by mouth pokeweed was used as a purgative and as an emetic. The young leaves, if boiled and drained twice, are supposedly edible. 

When trees drop their leaves in autumn, the red, yellow, or orange colors, and hand, heart, fruit, or fan shapes are pretty to look at. Leaves are much like snowflakes, because each one is different in size, texture, and color. Like clouds on a summer day, leaves can take the shape of many different things. One of the shapes you can make when you put a few leaves together is a fish swimming in the sparkling blue sea—a Sparkling Sea Scene. 

---