An aroma compound, also known as odorant, aroma, fragrance, or flavor, is a chemical compound that has a smell or odor. A chemical compound has a smell or odor when it is sufficiently volatile to be transported to the olfactory system in the upper part of the nose. Generally molecules meeting this specification have molecular weights of 2-Acetyl-1-pyrroline (fresh bread, jasmine rice) 6-Acetyl-2,3,4,5-tetrahydropyridine (fresh bread, tortillas, popcorn) Lactones gamma-Decalactone intense peach flavor gamma-Nonalactone coconut odor, popular in suntan lotions delta-Octalactone creamy note Jasmine lactone powerful fatty fruity peach and apricot Massoia lactone powerful creamy coconut Wine lactone sweet coconut odor Sotolon (maple syrup, curry, fenugreek) Thiols Allyl thiol (2-propenethiol; allyl mercaptan; CH2=CHCH2SH) (garlic volatiles and garlic breath) (Methylthio)methanethiol (CH3SCH2SH), the “mouse thiol”, found in mouse urine and functions as a semiochemical for female mice Ethanethiol, commonly called ethyl mercaptan (added to propane or other liquefied petroleum gases used as fuel gases) 2-Methyl-2-propanethiol, commonly called tert-butyl mercaptan is added as a blend of other components to natural gas used as fuel gas. Butane-1-thiol, commonly called normal butyl mercaptan is a chemical intermediate. Grapefruit mercaptan (grapefruit) Methanethiol, commonly called methyl mercaptan (after eating Asparagus) Furan-2-ylmethanethiol, also called furfuryl mercaptan (roasted coffee) Benzyl mercaptan (leek or garlic-like) Miscellaneous compounds Methylphosphine and dimethylphosphine (garlic-metallic, two of the most potent odorants known) Phosphine (Green Apple, Zinc Phosphide poisoned bait) Diacetyl (Butter flavor) Acetoin (Butter flavor) Nerolin (orange flowers) Tetrahydrothiophene (added to natural gas) 2,4,6-Trichloroanisole (cork taint) Substituted pyrazines