Aliphatic hydrocarbons usually do not exhibit odors of interest or well-defined character. Nonetheless, certain cycloalkanes have been associated with typical and pleasant notes, such as fruity, green and floral. Aromatic hydrocarbons possess alternating double and single bonds between carbon atoms. The term ‘aromatic’ was assigned before the physical mechanism determining aromaticity was discovered, and was derived from the fact that many of these compounds have a sweet scent.