L88- Aromatic chemistry Flashcards
what position do halogens direct in an aromatic ring?
ortho/para
are halogens electron donating or withdrawing
electron withdrawing
why is OH a special group?
OH is a electron donator by conjugation BUT is also an electronegative atom so should withdraw electrons by an inductive effect
Why does the inductive effect take over when using halogens?
due to bad overlap of the p orbitals as they are not in the 2p orbital like carbon Cl is 3p, Br is 4p and I is 5p, unlike O and N that are 2p
when does a friedel-crafts reactions occur?
used to introduce an alkyl or acyl group to an
aromatic ring, it creates a new carbon-carbon bond
what species are required for a friedel-crafts reactions to occur?
carbon electrophile
a carbonation is prepared from an alkyl or acyl halide using a catalyst using AlCl3 (a Lewis acid)
how is an electrophile formed using a primary halide?
a catalyst polarises the carbon-halogen bond e.g. R–Cl+–AlCl3-
What is polyalkylation?
The electrophilic aromatic substitution can occur up to three times giving a mixture of products
what does the introduction of an alkyl residue?
activates the aromatic ring through induction (the negative charge on the ring is increased.
This makes it easier for a second (or third) reaction to occur
what is more stable? long carbon chain or tertiary structure?
tertiary
What does the introduction of a acyl group to an aromatic ring?
it reduces the activity of the aromatic ring, a electrons are withdrawn onto the carbonyl group
what is a Brønsted-Lowry acid?
a substance that can donate a proton
what is a Lewis acid?
a substance that can accept an electron pair
are alcohols stable?
not very as there is no resonance stabilisation
are aromatic alcohols stable?
resonance stabilisation is possible here
