Rings, acids and amines

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Disproving Kekule

Bond lengths
When analysing (x-rays) the shape of bromine it was seen as symettrical. Whereas C-C bonds and C=C bonds have different lengths.
The bond lengths were 0.139nm. When a C-C bond should be 0.153nm and C=C 0.134nm

Enthalpy change of hydrogenation
Kekule suggest three double bonds. Meaning enthalpy change of hydrogenation should be 3x that of hexene.
Hexene = -120Kjmol-1
Predicted benzene = -360Kjmol-1
Benzene = -208Kjmol-1
152Kjmol-1 less, benzene has much less energy than kekules structure; more stable, this energy is known as delocalisation energy. More stable, less reactive. 

Resistance to reaction (bromine water)
Didn't react with bromines like alkenes do, Nor does it take part in electrophillic addition. 

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The relative ease of bromination with phenol

Bromine reacts more readily with phenol than benzene, this is because:
The lone pair of electrons occupying the p-orbital on the oxygen atom are drawn to the benzene ring. 
Creates a higher electron density in the ring structure - Activated
Increased electron density, able to polarise bromine molecules, attracted strongly towards the ring structure.

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Building triglycerides

Fats = long term energy store. 
Triglycerides are triesters, made up of an alcohol called propane-1,2,3-triol (glycerol) and three fatty acid (long chain carboxylic acids) molecules.

Unsaturated = one or more doube bonds
Saturated = no double bonds
Unsaturated fats with one double bond: monounsaturated 
18:2 (9,12)
FIrst number indicates the number of carbon atoms
Second number indicates number of double bonds
Number in brackets indicated positions.

Triglycerides are formed by a condensation reaction between the 3 -OH groups and the 3 fatty acid tails, forming 3 ester linkages (bonds) and 3 molecules of water.  

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