Flashcards
Reactions of benzene
Cards in this deck (13)
- 1Difference between alkene and benzene reactionsAlkenes react in electrophilic because the bond is very negative. This doesn't happen to benzene unless it is hot benzene and ultraviolet light
- 2Why does benzene not undergo electrophilic additionThe negative charge is spread out due to the electron rings so the aren't areas of big electron densities, so it prefers electrophilic addition to maintain the stable ring
- 3General reaction of benzene and an electrophileIt results in a hydrogen atom being substituted for an electrophile
- 4Halogen carriersElectrophiles have to be very strong to attack benzene rings, and most compounds aren't polarised enough. A halogen carries accepts a lone pair from a halogen atom for example, and as the lone pair is pulled away and it becomes far more polarised
RCl --> AlCl3 = R+ AlCl4- - 5Halogenation of benzeneIt needs the presence of a halogen carrier catalyst and the halogen is substituted for a hydrogen following general reaction rules
- 6Making the electrophile for nitrationSulfuric acid is far stronger than nitric acid so it causes nitric acid to break down into the nitronium ion
- 7Nutrition of benzeneNeeds to be warmed with concentrated nitric and sulfuric acid and then follows the normal substitution of NO2, needs to be under 55C for mononitration
Must be done under reflux - 8AlkylationUse a halogen carrier, and a haloalkane.
Under reflux
C6H6 + R-X = C6H5R + HCl
The H+ ion reacts with the halide ion to regenerate the halogen carrier - 9AcylationForms phenylketones by reaction and acyl halide with benzene using a halogen carrier.
C6H6 + RCOCl = C6H5COR + HCl - 10What are Friedal craft reactionsThey are reactions in which a hydrogen is substituted for an alkyl or acyl carbon chain
- 11Phenol reactivity compared to benzeneOne of the lone pairs in the OH groups overlaps and joins the delocalised ring making it more electron dense (only one pit can add in because they have to be in the y orbitals). This makes it more vulnerable to electrophiles
- 12Electron donating groupsAll have lone pairs of electrons which are donated to the ring:
OH, NH2, when the are additional reactions it is to the 2,4 and 6 group - 13Electron withdrawing groupsDoesn't donate any electrons so the density of spread out:
NO2 is an example and means more substitutions will most likely happen on the 3 and 5 carbons
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- A-Level Chemistry (6.1) Flashcards on Reactions of benzene , created by Reuben Veysey-Smith on 21/11/2016.
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- Reuben Veysey-Smith
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