g benzene derivaivesllbeni o ames havebeen by UPA namv th um d its bas 空w之 ticity 8msoeSetmgna1n99ae,thean 22 For tri- and more highly substituted benzenes, the ring carbons are numbered to give the substituents the lowest set of numbers, as in cyclohexane nomenclature: The following benzene derivatives will be used often in this course: The naming of three substituted benzene systems do not follow IUPAC nomenclature in the Chemical Abstracts indexing preferences: phenol, benzaldehyde and benzoic acid. Ring substituted compounds of these substances are named by numbering the ring positions or using the prefixes o-, p- and m-. The carbon carrying the substituent giving the compound its base name is given the number 1. Several other common names have been accepted by IUPAC, including: A substituted benzene is called an arene. An arene, when used as a substituent, is called an aryl group (Ar). The parent aryl substituent is phenyl, C6H5-. The group C6H5CH2- is called phenylmethyl (benzyl). Structure and Resonance Energy of Benzene: a First Look at Aromaticity 15-2 At room temperature, benzene is inert to acids, H2, Br2 and KMnO4, reagents that usually add to conjugated alkenes. The cyclic 6-electron arrangement of double bonds imparts a special stability in the form of a large resonance energy