EAS Reactions Flashcards
How does carbon-halogen bond strength change down Group 7?
Bond strength decreases down Group 7, with C-F as the strongest bond and C-I the weakest.
Why does the C-I bond break more easily than the C-Br bond in halogenoalkanes?
Because the C-I bond is weaker due to the lower electronegativity of iodine.
Why is the C-Cl bond in chlorobenzene stronger than in chloroalkanes?
The lone pair on the chlorine overlaps with the π electron system of the benzene ring, giving the bond π character and increasing its strength.
What conditions are required for a nucleophilic substitution reaction of chlorobenzene?
Chlorobenzene requires much higher temperature and pressure than chloroalkanes to react in nucleophilic substitution.
What reagents and conditions are needed for the bromination of benzene?
Reagents: Bromine. Conditions: Room temperature, in the dark, with AlBr3 or FeBr3 as a catalyst.
What type of reaction is the bromination of benzene?
Electrophilic substitution.
What is an alkylation reaction in benzene?
It’s a Friedel-Crafts reaction where an alkyl group is substituted into the benzene ring via electrophilic substitution.
What reagents and conditions are used for the alkylation of benzene?
Reagents: Chloromethane. Conditions: Reflux in anhydrous conditions with AlCl3 catalyst.
What is aromaticity?
Aromatic compounds have a ring structure with a delocalized pi system of electrons.
Describe the structure of benzene.
Benzene (C6H6) is a planar, cyclic compound with bond angles of 120° and a delocalized π electron system.
Why does benzene not undergo addition reactions like alkenes?
Benzene’s stable delocalized pi electron system prevents disruption during addition reactions, making it more likely to undergo electrophilic substitution.
How does benzene’s carbon-carbon bond length compare to single and double bonds?
The carbon-carbon bond length in benzene is 139 pm, between a single and double bond length.
What evidence contradicts Kekule’s structure of benzene?
The bond length in benzene is equal, and the enthalpy change of hydrogenation is much less than predicted for Kekule’s alternating double bonds.
What is the resonance enthalpy of benzene, and what does it indicate?
The resonance enthalpy is 152 kJ/mol lower than predicted for Kekule’s structure, indicating extra stability due to the delocalized pi electron system.
