directing aromatics Flashcards
1
Q
what is the directing effect?
A
the presence of substituted groups on a benzene ring having effects on substitution of further groups
2
Q
how are substituted groups classified?
A
- by the effect they have on electron density of the ring
- releasing electrons increase density
- withdrawing electrons decrease density
3
Q
what is an example of an electron withdrawing group i need to know?
A
-NO2
nitro
4
Q
what are 2 examples of electron donating groups i need to know?
A
-OH phenol
-NH2 amine
5
Q
describe electron donating groups
A
- side chains which increase electron density
- allowing electrophiles to react faster than with benzene
- known as activating groups
- directs subsitution to 2 and 4
6
Q
what causes a group to be electron donating?
A
- electronegative oxygen has the effect of pushing electrons forcing areas of charge over 2,4,6
- induces negative dipoles
- these attract electrophiles more effectively so substitution occurs here
7
Q
describe electron withdrawing groups
A
- side chains that decrease electron density
- electrophiles react slower than with benzene
- known as deactivating groups
- direct substitution to position 3
8
Q
describe how substiutions occur for electron donating groups?
A
- oxygen has a lone pair
- the p orbital overlaps with the pi electron cloud
- the lone pair become delocalised
- electron density of the pi cloud increases
- electrophiles attracted more easily
- negative dipoles at 2,4,6
9
Q
A
