4.1.1 ARENES

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Describe the Kekule Structure of benzene
ring of C atoms with alternating single and double bonds/ constantly flipping between two isomers/ 3 C-C and 3 C=C bonds of the same length
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What evidence is there against the Kekule structure?
in X-ray diffraction studies all bonds are the same length
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Describe the delocalised model of benzene
6 porbitals containing 1e/ porbitals overlap above and below the ring/ forms a delocalised system of pi bonds/ planar structure with 120 bond angle/ C-C bonds all of same length/ delocalised electrons spread of more than 2 e
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What evidence is there for the delocalised model?
all C-C bonds same length/ enthalpy change data/ benzene is very stable - more than expected with kekule due to delocalised ring of electron
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What enthalpy change data supports the delocalised benzene model?
the expected enthalpy of the hydrogenation of benzene with 3C=C bonds is expected to be much more exothermic/ more energy is require dot break bonds, experimental value is much less exothermic
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Describe the reactions of arenes
due to stability benzene is unwilling to undergo addition reactions/ will undergo electrophilic substitution
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Why does benzene resist bromination? (in comparison to alkenes)
benzene e in pi bond are delocalised/ benzene has lowe e density than alkenes/ benzene polarises bromine less and induces weaker dipole that C=C in bromine/ alkenes e are localised in pi bond
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Describe the halogenation of benzene
AlCl3 catalyst/ electrophilic substitution produces halobenzene and acid
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Describe the nitration of benzene
warm benzene/ cont nitric acid/ conc sulphuric acid/ H2SO4 catalyst/ must be kept under 55oC otherwise multiple substitutions
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When naming a benzene compound, what is its name if it is not the main functional group?
prefix - phenyl
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What is phenol?
OH on C1/ makes it behave differently than benzene/ and differently to an alcohol
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Describe the solubility and acidity of phenol
v low solubility in water/ OH hydrogen bonds/ when dissolves behaves as a very weak acid/ undergoes acid-base reactions
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What is a salt?
species where H+ ion has been replaced by another cation ion
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Why does phenol not react with metal carbonates?
not a strong enough base/ cannot remove H from the oxygen due to EN
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Explain the relative ease of bromination of phenol in comparison to benzene
phenol does react with bromine water because OH/ 1 of the lone pairs in a porbital of the O overlaps with the delocalised e ring/ increases density of the ring - especially 2,4,6/ phenol can polarise Br making it a better electrophile/ white ppt
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Describe the production of 2,4,6-tribromophenol
electrophilic substitution/ white ppt/ orange solution
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What are the uses of phenol?
antiseptics - TCP/disinfectants/ production of polymers and polycarbonates - epoxy resins for paints etc.
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Describe the esterification of phenol
reacts with COOH or acid anhydrides
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Other cards in this set

Card 2

Front

What evidence is there against the Kekule structure?

Back

in X-ray diffraction studies all bonds are the same length

Card 3

Front

Describe the delocalised model of benzene

Back

Preview of the front of card 3

Card 4

Front

What evidence is there for the delocalised model?

Back

Preview of the front of card 4

Card 5

Front

What enthalpy change data supports the delocalised benzene model?

Back

Preview of the front of card 5
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