organic chem chap 6.pdf - 1st Year Organic Chemistry...

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1stYearOrganic ChemistryChemical Engineering Diyala UniversityPage |1Benzene: Aromatic CharacterAliphatic and aromatic compoundsChemists have found it useful to divide all organic compounds into twobroad classes: aliphatic compounds and aromatic compounds. Theoriginal meanings of the words "aliphatic" (fatty) and "aromatic"(fragrant) no longer have any significance.Aliphatic compounds are open-chain compounds and those cycliccompounds that resemble the open-chain compounds. The families wehave studied so far alkanes, alkenes, alkynes, and their cyclic analogs areall members of the aliphatic class.Aromatic compounds are benzene and compounds that resemble benzenein chemical behavior. Aromatic properties are those properties of benzenethat distinguish it from aliphatic hydrocarbons. Some compounds thatpossess aromatic properties have structures that seem to differconsiderably from the structure of benzene: actually, however, there is abasic similarity in electronic configuration.Aliphatic hydrocarbons undergo chiefly addition and free radicalsubstitution;addition occurs at multiple bonds, and free-radicalsubstitution occurs at other points along the aliphatic chain. In contrast,aromatic hydrocarbons are characterized by a tendency to undergo ionicsubstitution.Other families of compounds (i.e., acids, amines, aldehydes, etc.) wherethe hydrocarbon parts of their molecules undergo reactions characteristicof either aliphatic or aromatic hydrocarbons. )It is important not to attach undue weight to the division betweenaliphatic and aromatic compounds. Although extremely useful, it is oftenless important than some other classification. For example, thesimilarities between aliphatic and aromatic acids, or between aliphaticand aromatic amines, are more important than the differences.
1stYearOrganic ChemistryChemical Engineering Diyala UniversityPage |2Cyclohexene vs benzeneREACTIONS OF BENZENE1.Nitration.2.Sulfonation.3.Halogenation.4.Friedel-Crafts alkylation.5.Friedel-Crafts aceylation.
1stYearOrganic ChemistryChemical Engineering Diyala UniversityPage |3In each of these reactions an atom or group has been substituted for oneof the hydrogen atoms of benzene. The product can itself undergo furthersubstitution of the same kind; the fact that it has retained the

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