The characteristic vanilla aroma found in many food and cosmetic products is due to a fragrant substance, vanillin, which is extracted from the vanilla plant. However, precisely because it is widely used in industry, natural vanillin is not sufficient to meet market demand and is also produced synthetically from guaiacol and eugenol (read Circular economy: from plastic to vanillin).
If you have not already done so, download Avogadro for free and watch the tutorials if necessary.
Study how the molecules of vanillin (4-hydroxy-3-methoxybenzaldehyde), eugenol (2-methoxy-4-prop-2-enylphenol) and guaiacol (1-hydroxy-2-methoxybenzene) differ by opening an Avogadro page for each compound and importing them (file → import → fetch by chemical name) with their respective IUPAC names. Indicate for each substance which functional groups you recognize and to which class of compounds it belongs.