Aromatic Hydrocarbons 2

Question 1

Why does the Carbocation in electrophilic substiution have resonance forms

Answer 1

Positive charge is shared among all Cs without double bond (triangle formation) to more evely distribute (delocalises) charge increasing stability while not aromatic

Question 2

Factor effecting how fast the electrophile attaches and position it attaches to the aromatic ring

Answer 2

Substituent (activators/deactivators). Can change if substituents undergoes oxidation/halogenation

Question 3

Activators Outline

Answer 3

Electron donating groups (give ring more negative charge). This makes electrophile attraction stronger. Eg CH3. Favours ortho and para products as they contain stable molecules ( neutral substituent attached to positively charged C in carbocation)

Question 4

Deactivators Outline

Answer 4

Electron accepting groups (decreases negative charge of ring). Makes electrophilic attraction weaker. Eg Cl, NO2. Favours meta as other 2 produce particularly unstable carbocations (positively charged substituent attached to positive carbon)

Question 5

Strongly Activating Groups Outline

Answer 5

Contain lone pairs that they add to electron cloud significantly increasing the net negativity of the ring. eg NH and OH

Question 6

Exception to deactivators placement rules

Answer 6

Halogens (electron withdrawers that can also donate a lone pair of electrons). Favour ortho and para

Question 7

Additive substituent effects

Answer 7

When 2 substituents guide the electrophile to the same place

Question 8

How is it decided what substituent directs electrophile placement if they are in opposition to each other

Answer 8

The stronger electron donor/acceptor

Question 9

Differences between electrophilic substitution and other reactions

Answer 9

Electrophilic makes direct changes to ring. Other reactions (eg oxidation, reduction, alkyl halogenation) effect substituents