aromatic compound
Related: Organic Chemistry

any of a large class of compounds that includes benzene 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 4 n + 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 alkenes . 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.


aryl group
Related: Organic Chemistry

(âr´Ĭl) , in chemistry, group of atoms derived from benzene or from a benzene derivative by removing one hydrogen that is bonded to the benzene ring (see radical ). The simplest aryl group is phenyl, C 6 H 5  ; it is derived from benzene. The tolyl group, CH 3 C 6 H 4 , is derived from toluene (methylbenzene). The xylyl group, (CH 3 ) 2 C 6 H 3 , is derived from xylene (dimethylbenzene). Just as several different alkyl groups may be derived from certain alkanes, so may several aryl groups be derived from certain aromatic compounds; for example, three different tolyl groups can be formed from toluene by removing hydrogen from different locations relative to the methyl group. When a functional group is joined with an aryl group, replacing the hydrogen that had been removed, a compound is formed whose characteristics depend largely on the functional group.

****From the patent description below:

[0169] "Aryl" refers to an unsaturated aromatic carbocyclic group of from 6 to 14 carbon atoms having a single ring (e.g., phenyl) or multiple condensed rings (e.g., naphthyl or anthryl). Preferred aryls include phenyl, naphthyl and the like.


[0154] "Alkaryl" refers to -alkylene-aryl groups preferably having from 1 to 10 carbon atoms in the alkylene moiety and from 6 to 10 carbon atoms in the aryl moiety. Such alkaryl groups are exemplified by benzyl, phenethyl and the like.

[0153] "Alkylene" refers to divalent alkylene groups preferably having from 1 to 10 carbon atoms and more preferably 1 to 6 carbon atoms. This term is exemplified by groups such as methylene (--CH.sub.2--), ethylene (--CH.sub.2CH.sub.2--), the propylene isomers (e.g., --CH.sub.2CH.sub.2CH.sub.2-- and --CH(CH.sub.3)CH.sub.2--) and the like.