Fichas
benzene
Fichas del conjunto (16)
- 1What is the formula for benzeneC6H6
- 2What are the two models proposed for the structure of benzene?- Kukule model
- Delocalised model - 3what is the Kukule's model of benzene?- Benzene was made up of a planar (flat) ring of carbon atoms with alternating single and double bonds between them
- Later dated the model to say that the benzene molecule was constantly flipping between two forms of isomers by switching over the double and single bond
- Therefore you would expect that the length of C-C is 154pm and C=C is 134pm - 4Evidence that do not support the Kukule structure1) The enthalpy of hydrogenation is less exothermic than expected, hydrogenation of benzene is -208kJmol-1 NOT -360Kjmol-1
2) All six carbon bonds in benzene are the same length
3) Benzene is resistant to addition reactions, it only reacts with a halogen carrier catalyst - 5What is the delocalised structure of benzene- Overlap of P-orbitals above and below the ring
- Pi electrons are delocalised around the ring
- C-C bonds are same length and strength between single and double bonds
- This creates high electron density above and below the ring - 6define electrophilic substitution- A substitution reaction is where an electrophile is attracted to an electron rich stop or part of a molecule and a new covalent bond is formed by the electrophile accepting an electron pair
- 7What is the equation and conditions needed for NITRATION- Is an Electrophilic substitution reaction
- Hydrogen atom is exchanged for a nitro group (-NO2)
conditions :
- Concentrated nitric acid (HNO3)
- Concentrated sulphuric acid as a catalyst (H2SO4)
- 50 degrees celcius
equation:
C6H6 + HNO3 -> C6H5NO2 + H2O - 8mechanism for Nitration1) is producing the electrophile ( nitronium ion)
2) electrophilic substitution
3) regeneration of the catalyst - 9how do you set up a nitration reaction- First the concentrated HNO3 and conc H2SO4 are mixed together in a flask held in an ice bath
-Then benzene is added and a reflux condenser is set up, keeping the mixture at 50 degrees to prevent further substitution reaction occurring
- 10what is the equation and conditions needed for Halogenation- Benzene does not react directly with a halogen as the aromatic ring is too stable
Reagents
- Cl2/Br2 and a halogen carrier catalyst
Conditions
- Reflux in the presence of a halogen carrier
Equation:
C6Hc + Cl2 -> C6H5Cl + HCl
- 11mechanism for Halogenation reaction
- 12Frieda Craft reactions, what is it and what are the two typesFriedal-Craft reaction is a substitution reaction where hydrogen is exchanged for an alkyl or acyl chain
1) Alkylation
-> puts any alkyl group onto a benzene ring
2) Acylation
-> Substitution with R-C=O
- Both adding extra C-C bond to the aromatic ring - 13Alkylation; reagents, conditions and overall equationReagents and conditions:
- Chloro-alkane (chloro-methane or chloro-ethane)
- Halogen carrier catalyst (e.g AlCl3)
- Anhydrous conditions
ibi
overal equation:
- 14Alkylation mechanism catalyst ; FeCl3 reagent ; Cl2
- 15Acylation; reagents, conditions and overall equationreagents and conditions;
- Halogen carrier catalyst (e.g AlCl3)
- Anhydrous conditions
overall equation:
- 16Acylation mechanism catalyst; FeCl3 reagent; CH3COCl
Información
- Descripción
- A-Level (a2 module 6) Chemistry Fichas sobre benzene , creado por Hina Nagano el 16/10/2016.
- Creado por
- Hina Nagano
- Visitas
- 5
- Valoración