3.10- Arene chemistry Flashcards
What are the 2 classes of organic chemicals
Aliphatic and arene
Explain the structure of benzene
. Each C atom is bonded to 2 other C atoms and one H atom by a single covalent bond, with the formula C6H6
. This leaves one unused electron on each C atom in the p orbital, perperndicular to the plane of the ring, the six p electrons are delocalised in a ring structure above and below the plane of carbon atoms
. Benzene is planar
What is the bond angle of the H-C-C bond
120 deg
How can you use enthalpies of hydrogenation to show the thermodynamic stability in benzene
The enthalpy for cyclohexene is -120KJmol-1 and theortetically if it was cyclo 1-3-5 triene the amount of energy would be 3 times this, however in the actual benzene the amound of energy is less, the 6 pi electrons are delocalised and are not arranged in 3 double bonds
The increase in stability connected to dissociation is called the delocalisation energy
What would the difference in hydrogenation values be for cyclohexa 1-3 dience and cyclohexa 1-4 diene
In 1-3 diene there would be some delocalisation and extra stability as the pi electrons are close together and they would overlap, the hydrogentation value would be more endothermic showing it is more stable, for 1-4 dione there is not any delocalisation as the pi electrons are too far apart so they do not overlap, the hydrogenation value would be -240Kjmol-1
What are the different ways for naming benzene
Simple molecule would be derivatives of benzene such as if there was a halogen,alkane,aldehyde,nitro and carboxylic acid group attached to benzene, also if there are two or more substituents are present then their positions much be indicated by the use of numbers
In other molecules the benzene is regarded as the substituent group on the other molecule just like an alkyl group. These include amines, alkene, branched alkanes, esters, ketones, alcohols and even some aldehydes
What reactions does benzene undergo
They do not go under addition becuase this would involve them breaking their delocalised systems, most of the benzene reactions involve substituting anothe hydrogen for an atom, they usually go undre electrophillic addition
What is the toxicity of benzene
Benzene is a carcinogen, and is banned for use in schools
Methylbenzene is less toxic and also reacts more readilty than benzene as the methyl side group releases electrons into the delocalised system making it more attractive to the electrophiles
What are the reagents/conditions for the reaction of benzene > nitrobenzene
Reagents- Concentrated nitric acid in the prescence of concentrated sulfuric acid catalyst
Mechanism- Electrophillic substitution
Why is the nitration of benzene an important reaction
Helps synthesis with useful compounds like TNT and formation of amines where dyes are manufactured etc
What is the IUPAC name for TNT
2 methyl- 1-3-5 trinitrobenzene
How do you form the NO2+ electrophile
Acid base reaction with the nitric acid and the sulfuric acid, the nitric acid loses a OH ion
What are the reagents/conditions for the reaction of benzene > phenyl ketone
Friedal crafts acylation
Reagents- Acyl chloride in the prescene of a anyhydroous aluminium chloride catalyst
Conditions: Heat under reflux
Mechanism: Eledctrophiling substitution
How is the electrphile formed for friedal crafts acylation
The AlCl3 gains a chlorine for the acyl chloride and the carboxylate ion is formed
What are the reagents/conditions for the reduction of a nitromamine
Reagent- Sn and HCl or Fe and HCl
Conditions- Heating
Mechanism- reduction
This reduction can also be done by catalytic hydrogenation
