Aromatic Chemistry - Benzene (8.1)
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What is any molecule containing a benzene ring called?
Aromatic
What is a aromatic carbon chain called?
Benzene
Numbering is only necessary for functional group greater than 1. True or False?
True
Sometimes the benzene ring is treated as a side chain. True or False?
True - when the functional group is complicated - prefix = phenyl
What is the historical name for benzeneamine?
Aniline
What is the historical name for benzenol?
Phenol
What is the historical name for methylbenzene?
Toulene
What is benzene?
• simplest arene • has 6 carbon atoms • in a hexagonal ring • each carbon atom = bonded to a hydrogen atom
What is stated in the kekulé structure of benzene?
• alternating double and single bonds • electrons localised in bonds • shows three C=C double bonds & C-C single bonds
What is stated in the modern structure of benzene?
• neither double nor single bonds - ring of delocalised elecrons above and below the plane of the ring
How can we disprove kekulé’s theory using bond lengths?
• by measuring bond lengths using X-ray diffractions • the accepted bond lengths for C-C is 0.154 & C=C is 0.135 • in kekulé’s structure, there are 3 C-C single bonds and 3 C=C double bonds • in the modern benzene, all bonds are the same length and bonds = 0.139 nm • with the modern version matching up
How can we disprove kekulé’s theory using enthalpy of hydrogenation?
• enthalpy of hydrogneation = amount of energy required to add hydrogen across hydrogen bond • kekule’s structure = -360kJ mol-1 • modern structure = -208kJ mol-1
How can we disprove kekulé’s theory using chemical reactions?
• kekulé’s structure = also known as “cyclohexa- 1,3,5 - triene • alkene + bromine water (turns colourless) • benzene + bromine water (stays orange/brown)
What does bonding in ethene look like?
• has a sigma bond and a pi bond
What does bonding look like in benzene?
• all six carbons = sp2 hybridised • has a delocalised pi-system • 6p orbitals • has sigma bonds (sp2 hybridized orbitals) • each carbon atom forms different bonds with the other similar carbon atoms instead of just one