CD 3, 4 Flashcards
define dye
a soluble, coloured, organic molecule that is able to bind to a substrate such as fibre, and impart colour to it
what was the problem with substances that imparted colour to items that couldn’t be used as dyes
they were too difficult to extract, did not bind strongly enough to cloth or faded too quickly
what is the formula of a phenyl group
C6H5
what is an Arene
aromatic compounds containing only C and H, also known at aromatic hydrocarbons
when naming a benzene ring, how do you know whether to use benzene or phenyl
- you use benzene when the benzene ring is the parent molecule, or when it is the only functional group
- You use phenyl when there is another functional group present or when a benzene ring has been substituted for another group
what is an aromatic compound
a compound that contains a a benzene ring
how do you know whether or not a structure is aromatic
- planar
- cyclic
- possessing 4n+2 delocalised pi electrons
what is the formula for the following groups:
- nitro group
- sulfonic acid group
nitro - NO2
sulfonic acid - SO3H
define feedstock
- the reactants that go into a chemical process
what is the formula for phenyl amine, and what is another name for it
C6H5NH2
aniline
what is an aromatic compound
a compound that contains benzene
define electrophile
a positive ion, or a molecule with a full or partial charge, that will be attracted to a negatively charged region and react by accepting a covalent bond
what does benzene reactive with and why
reacts with electrophiles because it is an area of high electron density
how do alkenes behave towards electrophiles
- react with electrophiles in addition reactions
- the product is a saturated molecule
how does benzene react react towards electrophiles
- react with electrophiles to undergo substitution reactions
- product contains an unsaturated benzene ring
- overall reaction is electrophilic substitution
why are reactions with benzene slow/ why is a catalyst typically used in reactions with benzene?
- because the first step in the reaction mechanism disrupts the delocalised electron system
- this requires a lot of energy
what is needed for bromination to occur, and what is produced
- benzene reacts with liquid bromine in the presence of a catalyst e.g. iron fillings and heat
- bromobenzene is produced
- bromine is decolourised and fumes of HBr are given off
what are the steps of the mechanism if iron is used as the catalyst
- 2Fe + 3Br2 —> 2FeBr3
- Br2 + FeBr3 —> Br+ + FeBr4 -
- Br+ + benzene —> bromobenzene + H+
- the catalyst is regenerated
H+ + FeBr4 - —> HBr + FeBr3
what catalyst is used in chlorination of benzene
aluminium chloride AlCl3
what conditions are needed for the chlorination of benzene to occur and why
- can occur at room temperature because both molecules are reactive
- must occur under anhydrous conditions because AlCl3 reacts violently with water
why are halogenated benzene derivatives important
- they are important intermediates in synthetic routes
- the carbon attached to the halogen can attack other carbon atoms and make C-C bonds
define alkylation
a reaction that introduces an alkyl group into a molecule
what is needed for alkylation to occur in benzene
what is formed
- benzene must be heated under reflux with chloroethane and anhydrous aluminium chloride
- ethylbenzene is formed
what is an acyl group
usually has the structure R-C=O, usually formed from a carboxylic acid or acyl chloride
define acylation
a reaction in which an acyl group is introduced to a molecule
what is a Friedel-Crafts reaction
- when a halogen carrier catalyst helps polarise organic molecules that contain halogens and cause them to be substituted with a benzene ring
Why are Friedel-Crafts reactions important?
- They are especially useful to synthetic chemists because they provide a way of adding carbon atoms to the benzene ring and building up side chains
write out the mechanism for chlorination of benzene
- benzene + Cl2 —> chlorobenzene + HCl (overall reaction)
- AlCl3 + Cl2 —> AlCl4 - + Cl+
- benzene + Cl+ —> chlorobenzene + H+
- Catalyst is regenerated
H+ + AlCl4 —> AlCl3 + HCl
if you want to add a methyl group to benzene, what do you react it with
chloroMETHANE
in the acylation of benzene, what can be used in replacement of acyl chloride
acid anhydride
what is the electrophile in the mechanism of the chlorination of benzene
Cl+
this card is just telling you to draw out the mechanism of acylation and chlorination of benzene 1000000 times xx
did you do it yet?
