Mention coffee, and caffeine is the chemical compound name that immediately springs to mind. However, whilst caffeine's effects on the brain are well documented — it binds to adenosine receptors in the brain — it has relatively little impact when it comes to the taste of coffee. (Compound Interest)
Coffee is a cornucopia of chemical compounds that influence its taste. One group of compounds about which plenty is known are the chlorogenic acids. In medium to light coffee brews, the main source of bitterness comes from the chlorogenic acids.