Fennel doesn't have a single chemical formula. It's a plant, and plants are complex mixtures of many different chemical compounds.

Here's why you can't pinpoint a single formula for fennel:

* Multiple Compounds: Fennel contains a vast array of chemicals, including essential oils (like anethole), flavonoids, vitamins, minerals, and more. Each of these compounds has its own unique chemical formula.

* Variations: The exact composition of fennel can vary depending on factors like growing conditions, variety, and even the part of the plant used.

If you're interested in specific chemicals in fennel, here are some examples:

* Anethole: C₁₀H₁₂O (the primary component of fennel oil, giving it its characteristic licorice-like flavor)

* Fenchone: C₁₀H₁₆O (another essential oil component)

* Vitamin C: C₆H₈O₆

To learn more about the specific chemicals in fennel, you can research "chemical composition of fennel" or "phytochemicals in fennel."