Chem. Test CH 17
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Electrophilic aromatic substitution:
attack on the electrophile by benzene makes sigma complex. show.
Electrophilic aromatic substitution
Loss of proton regains aromacity giving product.
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.
Formation of sigma complex is strongly ___thermic.
Benzene is _____ as reactive as ______.
Chlorination of Benzene.
Like Bromination, but instead of ___ you use ___.
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 ___.
Show oxidation of Iodine
H+ + HNO3 + 1/2 I2 ---> I+ + NO2 +H2O
Benzene + ___ Nitrobenzene
Mechanism behuind Nitrification (word?/+of NO2) of Benzene
Pre reaction: have to form electrophile... show
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.
+ what ? gives a aniline
and what does an aniline look like?
Zn, Sn, or Fe in aq HCl
Sulfonation of benzene
Start with benzene and ? --?--> ?
- 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
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
Toluene reacts ___ x faster than benzene
Methyl group of toluene is an ____, ____=director
Deuterium in heavy water with benzene
D2SO4 used instead
D3O+will continue if have enough to replace all
Put in order from strongest activating group to weakest
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?
If the atom attached to the benzene ring is positive at all, it will be a _______
Example of slightly positive atom attached to benzene causing it to be a _____ is what?
- meta director
NO2 is an example of a deactivating, meta-directing substituent. it requires --?--?--?> to be nitrated (add another NO2 group)
How does NO2 deactivate the ring?
It has a positive charge. Withdrawing electrongs from the ring. Less negative to react with electrophile.
Some meta directors,
Weird one, trimethylanilinium iodide
Halogens are _____ but ____ ____ directing
- ortho, para
____ groups are ususally stronger than ____ groups
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.
Benzene + ___ --?-->
- Lewis acid (AlCl3, FeBr3, etc)
Mechanism behind Friedel-Crafts Alkylation
Formaton of carbocation
Mechanism of Friedel-Crafts Alkylation
.... next steps
- electrophilic attack forms sigma complex.
- and Cl from AlCl4- removes proton giving
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.
Acyl groups named by dropping e and adding __
- ex. methanoyl
in Friedel-Craft acylation, can use an acyl group with X and ____ in ____ to substitute in the acyl group
alkylation v. acylation
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
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 ?
- HCl (aq) & Zn(Hg) (or Sn apparently)
The Clemmensen REduction takes the =___
of the acylbenzene, and makes it two __
CO + HCl
if you put it under ____
you will get ___
Gatterman-Koch formylation: Synthesis of Benzalkehydes
the necesary ingredients for formyl chloride __ and ___ along with ___ and ____ to give you the needed formyl cation
Nucleophilic Aromatic Substitution
Have to have electron withdrawing (____ in the example)
React with either ____ or ____
at ___ degrees C
In the addition elimination mechanism of nucleophilic aromatic substitution,
both the Cl and the OH are on the ring simultaneously forming a stable ______
After the nucleophile attacks the ring, the leaving group get's ______
in nucleophilic aromatic substitution
has to have ______ groups in the ___ or ____ postition in order to stabalize the intermediate.
- strong electron withdrawing groups
- ortho , para
____ gives nearest ___ extra stability
Toulene --?,?,?--> ---?--> Benzoic acid
- KMnO4, H2O, NaOH
In the side chain reaction of Permanganate oxidation the C has to have a ___ on it
Side chain reactions
replacing a hydrogen attached to a carbon with an X
involves a ____
X. draws off an ____ , add ___ ,
can do again!
- carbon radical
In the side chain halogenation, sometimes the ___ carbon will also gain a halide
the chlorine radicals are more reactive than the bromide ones
bromination is _____ than ____
so bromide will not react with the __ carbon
- more selective
In side chain halogenation with Br, you could also use ___
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