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Chemistry Y13 > O- Aromatics > Flashcards

O- Aromatics Flashcards

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1
Q

proposed structure of benzene by Kekule

A

cyclohexa-1,3,5-triene
alternating single + double bonds

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2
Q

Evidence that benzene is not a triene

A
  1. all bond lengths equal (X-ray diffraction)- lengths in betw C-C single & double
  2. enthalpy of hydrogenation ↓ than expected- thermodynamically, 152kJmol-1 ↑ stable than theoretical cyclohexa-1,3,5-triene
  3. x react by electrophilic addition (like alkenes)
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3
Q

Why are more reactive electrophiles needed to react with aromatic rings than alkenes?

A
  • involves initial disruption to ring
  • electrophiles must be ↑ powerful
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4
Q

Reagents for nitration

A
  1. conc nitric acid (HNO3)
  2. conc sulfuric acid (H2SO4)- catalyst
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5
Q

condition for nitration

A

reflux at 55C

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6
Q

uses of nitrated arenes

A
  • explosives
  • aromatic amines- industrial dyes
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7
Q

equation for generation of NO2+ electrophile

A

H2SO4 + HNO3 –> NO2+ + HSO4- + H2O

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8
Q

examples of electron-releasing groups

A

CH3, OCH3, OH, NH2

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9
Q

examples electron-withdrawing groups

A

NO2, COCl

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10
Q

state of benzene at room temp

A

colourless liquid

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11
Q

Why does benzene have a higher melting point than hexane?

A
  • flat molecule
  • pack tgt better- solid
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12
Q

What observation during combustion shows that the compound is an aromatic compound?

A

smoky flames
∵ high C:H ratio
- unburnt C remaining

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13
Q

Is phenol or ethanol a better nucleophile?

A

CH3CH2OH = better nuclephile
- alkyl group- slightly e- donating (O ↑ -ve)
- lone pair ↑ accessible to attack H in H2O
- delocalised e- in phenol –> ↑ stable
- ↓ available to nucleophile/ base

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14
Q

reagents for Friedel-Crafts Acylation

A
  1. anhydrous aluminium chloride AlCl3
  2. acyl chloride RCOCl
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15
Q

conditions for Friedel-Crafts Acylation

A
  1. reflux 50C
  2. dry inert solvent (ether)
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16
Q

RCOCl + AlCl3 –> RCO+ + AlCl4-
why does this reaction take place?

A
  • Al atom only has 6 e- in outer shell
  • readily accepts a lone pair
  • AlCl3- acid; RCOCl- base
17
Q

Reagents and conditions for reduction of nitrobenzene to phenylamine.

A

reagent- Sn (tin) in conc. HCl
conditions- heat + reflux

18
Q

equation for reduction nitrobenzene to phenylamine

A

C6H5NO2 + 6[H] –> C6H5NH2 + 2H2O

Chemistry Y13 (46 decks)

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