CD 3, 4

Question 1

define dye

Answer 1

a soluble, coloured, organic molecule that is able to bind to a substrate such as fibre, and impart colour to it

Question 2

what was the problem with substances that imparted colour to items that couldn’t be used as dyes

Answer 2

they were too difficult to extract, did not bind strongly enough to cloth or faded too quickly

Question 3

what is the formula of a phenyl group

Answer 3

C6H5

Question 4

what is an Arene

Answer 4

aromatic compounds containing only C and H, also known at aromatic hydrocarbons

Question 5

when naming a benzene ring, how do you know whether to use benzene or phenyl

Answer 5

• 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

Question 6

what is an aromatic compound

Answer 6

a compound that contains a a benzene ring

Question 7

how do you know whether or not a structure is aromatic

Answer 7

• planar
• cyclic
• possessing 4n+2 delocalised pi electrons

Question 8

what is the formula for the following groups:
- nitro group
- sulfonic acid group

Answer 8

nitro - NO2
sulfonic acid - SO3H

Question 9

define feedstock

Answer 9

• the reactants that go into a chemical process

Question 10

what is the formula for phenyl amine, and what is another name for it

Answer 10

C6H5NH2
aniline

Question 11

what is an aromatic compound

Answer 11

a compound that contains benzene

Question 12

define electrophile

Answer 12

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

Question 13

what does benzene reactive with and why

Answer 13

reacts with electrophiles because it is an area of high electron density

Question 14

how do alkenes behave towards electrophiles

Answer 14

• react with electrophiles in addition reactions
• the product is a saturated molecule

Question 15

how does benzene react react towards electrophiles

Answer 15

• react with electrophiles to undergo substitution reactions
• product contains an unsaturated benzene ring
• overall reaction is electrophilic substitution

Question 16

why are reactions with benzene slow/ why is a catalyst typically used in reactions with benzene?

Answer 16

• because the first step in the reaction mechanism disrupts the delocalised electron system
• this requires a lot of energy

Question 17

what is needed for bromination to occur, and what is produced

Answer 17

• 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

Question 18

what are the steps of the mechanism if iron is used as the catalyst

Answer 18

1. 2Fe + 3Br2 —> 2FeBr3
2. Br2 + FeBr3 —> Br+ + FeBr4 -
3. Br+ + benzene —> bromobenzene + H+
4. the catalyst is regenerated
   H+ + FeBr4 - —> HBr + FeBr3

Question 19

what catalyst is used in chlorination of benzene

Answer 19

aluminium chloride AlCl3

Question 20

what conditions are needed for the chlorination of benzene to occur and why

Answer 20

• can occur at room temperature because both molecules are reactive
• must occur under anhydrous conditions because AlCl3 reacts violently with water

Question 21

why are halogenated benzene derivatives important

Answer 21

• they are important intermediates in synthetic routes
• the carbon attached to the halogen can attack other carbon atoms and make C-C bonds

Question 22

define alkylation

Answer 22

a reaction that introduces an alkyl group into a molecule

Question 23

what is needed for alkylation to occur in benzene
what is formed

Answer 23

• benzene must be heated under reflux with chloroethane and anhydrous aluminium chloride
• ethylbenzene is formed

Question 24

what is an acyl group

Answer 24

usually has the structure R-C=O, usually formed from a carboxylic acid or acyl chloride

Question 25

define acylation

Answer 25

a reaction in which an acyl group is introduced to a molecule

Question 26

what is a Friedel-Crafts reaction

Answer 26

• when a halogen carrier catalyst helps polarise organic molecules that contain halogens and cause them to be substituted with a benzene ring

Question 27

Why are Friedel-Crafts reactions important?

Answer 27

• 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

Question 28

write out the mechanism for chlorination of benzene

Answer 28

1. benzene + Cl2 —> chlorobenzene + HCl (overall reaction)
2. AlCl3 + Cl2 —> AlCl4 - + Cl+
3. benzene + Cl+ —> chlorobenzene + H+
4. Catalyst is regenerated
   H+ + AlCl4 —> AlCl3 + HCl

Question 29

if you want to add a methyl group to benzene, what do you react it with

Answer 29

chloroMETHANE

Question 30

in the acylation of benzene, what can be used in replacement of acyl chloride

Answer 30

acid anhydride

Question 31

what is the electrophile in the mechanism of the chlorination of benzene

Answer 31

Cl+

Question 32

this card is just telling you to draw out the mechanism of acylation and chlorination of benzene 1000000 times xx

Answer 32

did you do it yet?