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Electrophilic aromatic substitution:
Step one
attack on the electrophile by benzene makes sigma complex. show.
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Electrophilic aromatic substitution
Step two
Loss of proton regains aromacity giving product.
show.
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Bromination of benzene
- Br is not electrophilic enough to react with benzene. So catalyst needed.
- Makes the Br react more like Br+
- and also, FeBr4- complex acts like weak base to remove proton from complex.
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Formation of sigma complex is strongly ___thermic.
endo
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Benzene is _____ as reactive as ______.
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Chlorination of Benzene.
Like Bromination, but instead of ___ you use ___.
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Iodination of benzene.
Instead of a catylist, this reaction requires an acidic oxidizing agent. Which is?
The I+ electrophile used results from oxidation of ___ by ___.
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Show oxidation of Iodine
H+ + HNO3 + 1/2 I2 ---> I+ + NO2 +H2O
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Benzene + ___ Nitrobenzene
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Mechanism behuind Nitrification (word?/+of NO2) of Benzene
Pre reaction: have to form electrophile... show
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Describe steps 1 and 2 of nitration of benzene after NO2+ is produced
- End up with -O-N=O attached at the N
- reacts just like bromination etc. HSO4- pulls the extra proton off.
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Nitrobenzene
+ what ? gives a aniline
and what does an aniline look like?
Zn, Sn, or Fe in aq HCl
- aniline:
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Sulfonation of benzene
Start with benzene and ? --?--> ?
- SO3
- H2SO4 takes away extra proton
- after it has it's extra proton, gives it to the -O that is now attached to molecule. thus you have this
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You can undo Sulfonation of benzene with
benzene sulfonic acid + ? + ? + ? to get
benzene, H3O+, and ?
can use this to force Cl etc on ortho position
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Toluene reacts ___ x faster than benzene
because Activated
Methyl group of toluene is an ____, ____=director
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Deuterium in heavy water with benzene
D2SO4 used instead
D3O+will continue if have enough to replace all
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Put in order from strongest activating group to weakest
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What is added to the reaction of aniline (benzene with NH2) so that when you add Br2 and H2O the HBr produced will not protonate the NH2?
NaHCO3
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If the atom attached to the benzene ring is positive at all, it will be a _______
meta director
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Example of slightly positive atom attached to benzene causing it to be a _____ is what?
- meta director
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NO2 is an example of a deactivating, meta-directing substituent. it requires --?--?--?> to be nitrated (add another NO2 group)
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How does NO2 deactivate the ring?
It has a positive charge. Withdrawing electrongs from the ring. Less negative to react with electrophile.
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Some meta directors,
NO2
S___
__N
___C=O
_____C=O
Weird one, trimethylanilinium iodide
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Halogens are _____ but ____ ____ directing
- electronegative
- ortho, para
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____ groups are ususally stronger than ____ groups
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The Friedel-Crafts Alkylation
define / describe briefly
In the presence of a lewis acids such as AlCl3 and FeCl3, alkyl halides alkylate benzene to give alkylbenzenes.
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Friedel-Crafts alkylation
Benzene + ___ --?-->
- R-X
- Lewis acid (AlCl3, FeBr3, etc)
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Mechanism behind Friedel-Crafts Alkylation
Formaton of carbocation
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Mechanism of Friedel-Crafts Alkylation
.... next steps
- electrophilic attack forms sigma complex.
- and Cl from AlCl4- removes proton giving
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In primary alkyl halides, the Friedel-Crafts alkylation mechanism....
- it just forms a complex with a partial positive charge on the primary
- carbon in which case they Do bond, and the others just get "kicked off"
- then it procedes to remove proton.
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Acyl groups named by dropping e and adding __
-oyl
- ex. methanoyl
- ethanoyl
- propanoyl
- benzoyl
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in Friedel-Craft acylation, can use an acyl group with X and ____ in ____ to substitute in the acyl group
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Compare
alkylation v. acylation
3 things
Alkylation: 1. cannot work with strongly deactivated derivatives. 2. may rearrange. 3. Polyalkylation is a problem
Acylation: 1. cannot work with strongly deactivated derivatives. 2. resonance-stabilized acylium ions don't rearrange. 3. formation of deactivated acylbenzene does not react further
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Clemmensen Reduction: Synthesis of Alkylbenzenes
Use ____ to make an __1__benzene
Then reduce to ____benzene using this reduction
What do you add to the 1 ?
- Friedel-Crafts
- acyl-
- alkyl-
- HCl (aq) & Zn(Hg) (or Sn apparently)
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The Clemmensen REduction takes the =___
of the acylbenzene, and makes it two __
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CO + HCl
if you put it under ____
you will get ___
- Pressure
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Gatterman-Koch formylation: Synthesis of Benzalkehydes
the necesary ingredients for formyl chloride __ and ___ along with ___ and ____ to give you the needed formyl cation
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Nucleophilic Aromatic Substitution
Have to have electron withdrawing (____ in the example)
React with either ____ or ____
at ___ degrees C
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In the addition elimination mechanism of nucleophilic aromatic substitution,
both the Cl and the OH are on the ring simultaneously forming a stable ______
sigma complex
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After the nucleophile attacks the ring, the leaving group get's ______
knocked off!!
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in nucleophilic aromatic substitution
has to have ______ groups in the ___ or ____ postition in order to stabalize the intermediate.
- strong electron withdrawing groups
- ortho , para
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Side-Chain reaction
Permanganate oxidation
____ gives nearest ___ extra stability
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Side-chain reaction
Permanganate oxidation
Toulene --?,?,?--> ---?--> Benzoic acid
- KMnO4, H2O, NaOH
- H+
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In the side chain reaction of Permanganate oxidation the C has to have a ___ on it
H
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Side chain reactions
replacing a hydrogen attached to a carbon with an X
involves a ____
X. draws off an ____ , add ___ ,
can do again!
need light
- carbon radical
- electron
- HCl
- X2
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In the side chain halogenation, sometimes the ___ carbon will also gain a halide
beta
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the chlorine radicals are more reactive than the bromide ones
bromination is _____ than ____
so bromide will not react with the __ carbon
- more selective
- chlorination
- beta
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In side chain halogenation with Br, you could also use ___
NBR
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