AC 5-10 Flashcards
How water soluble is phenol?
Slightly. It has an OH group, so it can form hydrogen bonds with water molecules, but it also has a large non-polar hydrocarbon part, which cannot form hydrogen bonds.
How acidic is phenol?
Very slightly. It only reacts with strong bases, such as hydroxides, but not weak bases, such as carbonates.
Why is phenol acidic?
When H+ dissociates from phenol, it leaves behind a negative phenoxide ion. This negative charge can delocalise into the pi-electron system of the aromatic ring, so it becomes stable.
Why does phenol undergo electrophilic substitution more easily than benzene?
The lone pair of electron within a p-orbital on the oxygen can delocalise into the pi-electron system of the ring. This increases its electron density, making it more attractive to an electrophile. The ring is said to be activated.
Where would substitution normally occur on phenol?
At the 2,4 and 6 positions.
Phenol reacts with bromine without a catalyst. What is observed?
The bromine is decolourised, and a white precipitate is formed.
How can phenol be nitrated?
By reacting with aqueous nitric acid. There is no need for a catalyst.
Give 2 electron donating groups.
OH and NH2.
State an electron withdrawing group.
NO2.
What effects do electron-withdrawing groups have?
- They make the ring less attractive to electrophiles by decreasing electron density.
- If they are strongly deactivating, then direct substitution occurs at the 3 position.
When calculating the Kc of a reaction, what must be ignored?
Any reactants or products that are solid or pure liquid. The
The higher the numerical value of Kc…
The further to the right an equilibrium lies.
What does Kc depend on?
Kc is temperature dependent only.
What are isomers?
Different compounds with the same molecular formula.
What are structural isomers?
Compounds with the same molecular formula but different structural formula.
