aromatic compound

aromatic compound,

any of a large class of compounds that includes benzenebenzene
, colorless, flammable, toxic liquid with a pleasant aromatic odor. It boils at 80.1&degC; and solidifies at 5.5&degC;. Benzene is a hydrocarbon, with formula C₆H₆.
..... Click the link for more information. and compounds that resemble benzene in certain of their chemical properties. Originally applied to a small class of pleasant-smelling chemicals derived from vegetables, it now encompasses a wide diversity of compounds with no connection to the sense of smell. Common aromatic compounds other than benzene include toluene, naphthalene, and anthracene (all of which are present in coal tar). Each of these compounds contains at least one ring that consists of six carbon atoms, each joined to at least two other carbon atoms, and each joined to adjacent carbon atoms by one single and one double bond. The resulting hexagonal structure is characteristic of many aromatic compounds. The general rule is that aromatic molecules have 4n + 2 delocalized electrons (where n is an integral number). Thus the number of delocalized electrons in benzene (6), naphthalene (10), and anthracene (14) agree with their aromatic character. On the other hand, the eight-membered cyclic compound with four alternating double bonds (cyclooctatetraene) is not aromatic and shows reactivity similar to alkenesalkene
, any of a group of aliphatic hydrocarbons whose molecules contain one or more carbon-carbon double bonds (see chemical bond). Alkenes with only one double bond have the general formula C_nH_2n.
..... Click the link for more information. . For this reason, the bonds in the aromatic ring are less reactive than ordinary double bonds; aromatic compounds tend to undergo ionic substitution (e.g., replacement of a hydrogen bonded to the ring with some other group) rather than addition (which would involve breaking one of the resonant bonds in the ring). Presence of the six-membered benzene ring is not essential for aromatic compounds; for example, furan, a heterocyclic compound that has a five-membered ring that includes an oxygen atom, has aromatic properties, as does pyridine, a heterocyclic compound whose six-membered ring includes a nitrogen atom.

aromatic compound

cy·clic com·pound

any compound in which the constituent atoms, or any part of them, form a ring. Used mainly in organic chemistry where: 1) numerous compounds contain rings of carbon atoms (carbocyclic compounds) or carbon atoms plus one or more atoms of other types (heterocyclic compounds), usually nitrogen, oxygen, or sulfur; 2) where the atoms in the ring are all of the same element (homocyclic or isocyclic compound); 3) where the ring is saturated or contains nonconjugated double bonds (alicyclic compound), the compound is similar in properties to the corresponding acyclic compound (for example, cyclohexane resembles hexane); 4) where the ring contains conjugated double bonds in a closed loop in which there are 4n + 2 (where n is an integer) delocalized π electrons (Hückel rule) (aromatic compound; for example, benzene, pyridine), it is more stable than the corresponding saturated ring and exhibits unusual chemical properties characteristic of itself and not of other types of rings or of acyclic compounds. These aromatic compounds have the ability to sustain an induced ring current. Synonym(s): closed chain compound, ring compound

cy·clic com·pound

(sik'lik kom'pownd) Any compound in which the constituent atoms, or any part of them, form a ring. Used mainly in organic chemistry.
Synonym(s): closed chain compound.