Final answer:
To determine if a molecule is aromatic or aliphatic, evaluate its structure: aromatic hydrocarbons have a ring structure with alternating double bonds following Huckel's rule (4n+2 pi electrons), while aliphatic hydrocarbons do not and are classified as alkanes, alkenes, or alkynes based on the absence or presence of carbon-carbon double or triple bonds.
Step-by-step explanation:
To determine whether a molecule is aliphatic or aromatic, we must look at the structure and bonding of the molecule. An aromatic hydrocarbon has a ring structure with alternating double bonds that follows Huckel's rule, which states that there must be a certain number (4n+2) of pi electrons. In contrast, aliphatic hydrocarbons do not contain such a ring. Aliphatic hydrocarbons can be further classified into alkanes, which have only single bonds, alkenes, which have at least one carbon-carbon double bond, and alkynes, which have at least one carbon-carbon triple bond.
To identify if a molecule is aromatic or aliphatic, we examine its molecular structure. For an aromatic hydrocarbon, common examples include benzene and naphthalene, which possess the characteristic ring with delocalized pi electrons. If the molecule does not have such a ring structure, it is aliphatic. For aliphatic hydrocarbons, we further check if there are carbon-carbon double or triple bonds to determine if it's an alkene or alkyne, respectively. If there are none, and all carbon-carbon bonds are single, it is an alkane.