Aromatic Compounds Flashcards
What are the conditions needed for nitration of Benzene?
Concentrated H₂SO₄ and concentrated HNO₃ in a 2:1 ratio at 60°C
Why must you not go above 60°C when nitrating benzene?
Otherwise more nitro groups will be substituted onto the benzene ring
Conditions needed for Friedel Crafts acylation?
heat under reflux 50
Why is methylbenzene more reactive than benzene?
The methyl side group releases electrons into the delocalised system making it more attractive to electrophiles.
What are aliphatic substances?
Substances which are straight or branched chain organic substances.
What are aromatic substances?
Includes one or more ring of six carbon atoms with delocalised bonding
What evidence is there to show that benzene wasn’t the structure that kekule thought?
The bond lengths should be different with the double bonds being shorter than the single bonds yet they were all the same length between these two lengths.
Benzene doesn’t readily undergo substitution reactions
Explain the bonding in and the shape of a benzene molecule.
Each carbon has 3 covalent bonds
The spare electrons from the p orbital become delocalised and form a pi cloud above and below the ring.
Benzene is Planar
C-C bond lengths are all the same
bond angle is 120
Expected H Hydrogenation of cyclohexatriene = -360KJmol
H hydrogenation benzene is less exothermic by 152KJmol
Benzene is lower in energy than cylcohexatriene/benzene is more stable
Why isnt the enthalpy of hydrogenation of cyclohexa1,3diene double that of cyclohexene?
Double bonds are separated by one single bond
allows some delocalisation/overlap of p orbitals
Is benzene more stable than cyclohexatriene?
Yes
Because of delocalisation / resonance
Why is cyclohexa-1,3-diene more stable than cyclohexane-1,4-diene?
In cyclohexa-1,3-diene ther would be some delocalisation and extra stability as the pi electrons are close together and so overlap
