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Chem 104 Lecture 4
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9
Chemistry
Undergraduate 1
02/26/2013

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Term
electron-donating groups .......... the ring and direct to ortho/......
Definition

activate

para

Term

which of the following is not an ortho/para director?

 

-NH2 amino

-OH hydroxy

-NO2 nitro

-X halogen

Definition

-NO2 is not an ortho/para director. it is a meta director.

 

 

the following are ortho/para directors (electron-donating groups)

NH2, -OH, -OR, -R, -X

amino, hydroxy, alkoxy, alkyl and halogen

Term
electron-withrawing groups .......... the ring and direct to ...........
Definition

deactivate

meta

 

NO2, -SO3H, -CN, -COOR, -COR/-CHO are all electron-withdrawing meta directors.

 

nitro, sulphonic acid, nitrile, ester or acid, acyl or formyl

Term
if an alkoxy group was to meta direct, the arenium ion would be a resonance hybrid of how many lewis structures?
Definition

3.

therefore the alkoxy group directs ortho/para because the intermediate has a more stable 4 lewis structured resonance hybrid which results in more effective charge delocalisation than those for meta substitution

Term

ortho/para directors:

any substituent with a ...... ...... on the atom directly bound to the ring behaves like the -OCH3 group and stabilises the arenium ion intermediates for otho/para substitution

Definition

lone pair.

 

NH2, -OH, -OR, -R, -X are all ortho/para directors

Term
why is the resonance effect more dominant than the inductive effect?
Definition
it gives the intermediates for ortho/para substitution a 4th resonance form.
Term

true or false

the intermediates for ortho/para substitution are more stable than the intermediate for meta substitution

Definition
this is true
Term
in which substituiton of nitrobenzene does the nitro group prevent charge delocalisation  in the arenium ion
Definition
ortho/para substituiton. charge distribution on the arenium ion in ortho/para substitutions of nitrobenzene is strongly disfavoured
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