Benzene + Phenol Flashcards
1
Q
Explain the 3 pieces of evidence that led scientists to doubt the model proposed by Kekule.
A
- hydration enthalpy of benzene was less exothermic than expected
- x ray diffraction showed all carbon-carbon bonds were the same length, but c=c (double) shorter than c-c single bond
- benzene does not decolorise bromine water, therefore, has no c=c bonds and does not undergo electrophilic addition
2
Q
what is an electrophile + what is it attracted to ?
A
- an electron-deficient species that can accept a pair of electrons
- attracted to high e- density
3
Q
Friedel crafts reaction of benzene
A
- halogenation
- alkylation = adding CH3 etc
- Acylation = adding RC=O eg . CH3COCl + ALCL3 —-> AlCl4- + CH3CO +
remeber electrophole is thing thats addedon with a + sign and for acyl + alkyl ation add cl or br to end of molecule added on
4
Q
what does phenol react and not react with ?
A
- reacts with strong bases such as NaOH
- does not react with weak bases like metal carbonates
5
Q
what is formed during Bromination of phenol
A
- produces 2,4,6-tribromophenol and HBr
- bromine is decolourised + white precipitate is formed
6
Q
what conditions are needed for nitration of benzene
A
= concentrated nitric + sulphuric acid
= temp below 55 degrees
7
Q
what are delocalised pi bond electrons
A
- delocalised e- are spread over more than 2 atoms
- pi bond formed by sideways overlap of p-orbitals above and below the plane
8
Q
structure an bonding of benzene
A
- c-c bonds same length
- sideway overlap of p orbitals above and below ring forms pi bond
- has 6 delocalised e -
- 120 degree bond angle
