Aromaticity Organic compounds aliphaticaromatic Benzene and related compounds. open-chain compounds and ring compounds that are chemically similar to open-chain compounds.
Benzene (C 6 H 6 ) is the simplest aromatic hydrocarbon (or arene). Benzene
Planar: bond angles are 120°, carbon–carbon bond lengths are the same length and intermediate in length between single and double bonds. Undergoes substitution rather than electrophilic addition
Aromaticity and the Hückel 4n+2 Rule 1- aromatic compounds are: Planar. cyclic molecule. ( Conjugated cyclic) : resonance all over the ring. Obey Huckel’s rule : “ The cloud must contains a total of (4n+ 2 ) electrons “ 43210n n+2
2-Anti-Aromatic Compounds are: Conjugated cyclic, planar, The number of π electons = (4n) no. of π e = 4, 8, 12, 16, 20, …etc. 2 double bond 4 π electron
3-Non-Aromatic Compounds are: A non-planar non-conjugated.
Classify the following compounds into aromatic, anti-aromatic and non-aromatic? =CH 2
Nomenclature for benzene: A. monosubstituted benzenes: 1. Common names:
2. Substituted benzene:
ortho- meta- para- 1,2- 1,3- 1,4- B. Disubstituted benzenes: When two substituents are on benzene, three constitutional isomers are possible:
3- three or more substituents 1.Substituent's locations are specified by numerals. 2. If any of the substituents imparts a special name, then the molecule is named as a derivative of that substituent. 3. If there is no special name, then the substituents are named in alphabetical order with the lowest possible set of numbers.
When a benzene ring is a substituent, the term phenyl is used (for C 6 H 5 ) You may also see “Ph” in place of “C 6 H 5 ” “Benzyl” refers to “C 6 H 5 CH 2 ”
Give name for the following:
Solution: 1-bromo-3-chlorobenzene m-bromochlorobenzene (3-methylbutyl)benzene iso-butylbenzene 4-bromoaniline p-bromoaniline 2,5-dichlorotoluene 1,4-dichloro-2-methylbenzene 1-ethyl-2,4-dinitrobenzene 1,2,3,5-tetramethylbenzene