Bonding
3.3.10.1:
The nature of the bonding in a benzene ring, limited to planar structure and bond
length intermediate between single and double
Delocalisation of p electrons makes benzene more stable than the theoretical
molecule cyclohexa-1,3,5-triene
Students should be able to:
use thermochemical evidence from enthalpies of hydrogenation to account for
this extra stability
explain why substitution reactions occur in preference to addition reactions
What is benzene’s formula and structure?
C6H6
What is another name for arenes? Why did this come about?
Aromatic compounds, as first found in sweet-smelling dyes
Dangers of benzene? (why it is not used in schools)
It is a carcinogen
What is the shape of benzene?
Bonding 1
, Flat, regular hexagon
Bond angle = 120*
Describe the bonding in benzene
there are sigma bonds between each C-C bond
this creates a planar shape with bond angle of 120* with the hydrogens
there are also pi-bonds due to the delocalised electrons in the delocalised pi-
system, making benzene stable
What happens to the 4th electron in the p orbital of each C atom in benzene?
It delocalises to form rings of electron density above & below the hexagon,
forming rings of delocalised electron density above/below the hexagon
forms a delocalised pi system
What is the effect on benzene’s stability of the rings of electron density?
Makes benzene very stable
Bonding 2
3.3.10.1:
The nature of the bonding in a benzene ring, limited to planar structure and bond
length intermediate between single and double
Delocalisation of p electrons makes benzene more stable than the theoretical
molecule cyclohexa-1,3,5-triene
Students should be able to:
use thermochemical evidence from enthalpies of hydrogenation to account for
this extra stability
explain why substitution reactions occur in preference to addition reactions
What is benzene’s formula and structure?
C6H6
What is another name for arenes? Why did this come about?
Aromatic compounds, as first found in sweet-smelling dyes
Dangers of benzene? (why it is not used in schools)
It is a carcinogen
What is the shape of benzene?
Bonding 1
, Flat, regular hexagon
Bond angle = 120*
Describe the bonding in benzene
there are sigma bonds between each C-C bond
this creates a planar shape with bond angle of 120* with the hydrogens
there are also pi-bonds due to the delocalised electrons in the delocalised pi-
system, making benzene stable
What happens to the 4th electron in the p orbital of each C atom in benzene?
It delocalises to form rings of electron density above & below the hexagon,
forming rings of delocalised electron density above/below the hexagon
forms a delocalised pi system
What is the effect on benzene’s stability of the rings of electron density?
Makes benzene very stable
Bonding 2
