Chemsheets AS006 (Electron arrangement)

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Electrophilic Substitution Reactions

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Presentation transcript:

Chemsheets AS006 (Electron arrangement) 24/04/2017 www.CHEMSHEETS.co.uk AROMATIC CHEMISTRY © www.chemsheets.co.uk A2 019 15-Jul-12

STRUCTURE OF BENZENE Benzene = C6H6 Its structure was a mystery for many years - until Kekule’s dream.

STRUCTURE OF BENZENE Problems with Kekule’s structure: 1) C-C bonds are all the same length (between C-C and C=C length). 2) Benzene does not undergo addition reactions readily (e.g. with bromine water). 3) H hydrogenation about 152 kJ mol-1 less than expected. © www.chemsheets.co.uk A2 019 15-Jul-12

STRUCTURE OF BENZENE

STRUCTURE OF BENZENE http://www.isis.stfc.ac.uk/

HYDROGENATION OF BENZENE © www.chemsheets.co.uk A2 019 15-Jul-12

NAMING AROMATIC COMPOUNDS benzenecarboxylic acid methylbenzene (toluene) chlorobenzene nitrobenzene benzenecarboxylic acid (benzoic acid) © www.chemsheets.co.uk A2 019 15-Jul-12

NAMING AROMATIC COMPOUNDS 1,3-dimethylbenzene (m-xylene) 4-methyl-1-chlorobenzene 2-hydroxybenzenecarboxylic acid 3,5-dinitrobenzenecarboxylic acid © www.chemsheets.co.uk A2 019 15-Jul-12

NAMING AROMATIC COMPOUNDS phenylamine (aniline) 2-phenylbutane phenylethene phenylethanone © www.chemsheets.co.uk A2 019 15-Jul-12

NAMING AROMATIC COMPOUNDS methyl benzenecarboxylate phenylethanoate methyl benzenecarboxylate (methyl benzoate) N-phenylethanamide © www.chemsheets.co.uk A2 019 15-Jul-12

NAMING AROMATIC COMPOUNDS phenol benzene-1,2-diol 2-nitrophenol 2,4,6-trichlorophenol (TCP) © www.chemsheets.co.uk A2 019 15-Jul-12

NITRATION Conditions conc HNO3 conc H2SO4 catalyst 50ºC nitrobenzene © www.chemsheets.co.uk A2 019 15-Jul-12

NITRATION – ELECTROPHILIC SUBSTITUTION Formation of electrophile HNO3 + 2 H2SO4 + 2 HSO4- + H3O+ NO2 + nitronium ion Reaction of electrophile with aromatic compound NO2 + NO2 + NO2 -H H + © www.chemsheets.co.uk A2 019 15-Jul-12

NITRATION Equation (name product) Conditions Mechanism © www.chemsheets.co.uk A2 019 15-Jul-12

NITRATION Conditions conc HNO3 conc H2SO4 catalyst 50ºC 2-methylnitrobenzene Conditions conc HNO3 conc H2SO4 catalyst 50ºC © www.chemsheets.co.uk A2 019 15-Jul-12

NITRATION Uses of nitro compounds: 1) as explosives 2) to make aromatic amines (used to make dyes) 1,3,5-trinitrotoluene TNT © www.chemsheets.co.uk A2 019 15-Jul-12

FRIEDEL-CRAFTS ACYLATION aromatic ketone Conditions AlCl3 catalyst © www.chemsheets.co.uk A2 019 15-Jul-12

FRIEDEL-CRAFTS ACYLATION WARNING! - do not mix Friedel-Crafts acylation & other acylations (needs AlCl3) Swap H on benzene ring for acyl group Swap H on O/N for acyl group © www.chemsheets.co.uk A2 019 15-Jul-12

FRIEDEL-CRAFTS ACYLATION WARNING! - Classic question to test this H replaced is on N not benzene ring. This is NOT Friedel-Crafts acylation! © www.chemsheets.co.uk A2 019 15-Jul-12

FRIEDEL-CRAFTS ACYLATION – ELECTROPHILIC SUBSTITUTION Formation of electrophile O AlCl3 + RCOCl AlCl4 – + R C + acylium ion OR O O O O – R-C-O-AlCl3 + AlCl3 + R-C-O-C-R R C + acylium ion © www.chemsheets.co.uk A2 019 15-Jul-12

FRIEDEL-CRAFTS ACYLATION – ELECTROPHILIC SUBSTITUTION Reaction of electrophile with aromatic compound + C O R O O C R + C R -H H + Regeneration of catalyst AlCl4 – + H+ AlCl3 + HCl or O O – R-C-O-AlCl3 + H+ R-C-OH + AlCl3 © www.chemsheets.co.uk A2 019 15-Jul-12

FRIEDEL-CRAFTS ACYLATION Equation Conditions Mechanism © www.chemsheets.co.uk A2 019 15-Jul-12

FRIEDEL-CRAFTS ACYLATION Conditions AlCl3 catalyst © www.chemsheets.co.uk A2 019 15-Jul-12