Benzene

Question 1

Delocalisation of electrons

Answer 1

A delocalised electron is an electron in an atom, ion or molecule that is not associated with any ingle atom or single covalent bond

Question 2

Electrophile

Answer 2

An electron par acceptor

Question 3

Substitution reaction

Answer 3

A reaction in which an atom or group of atoms is replaced with a different atom or group of atoms

Question 4

Addition reaction

Answer 4

A reaction in which a reactant is joined to an unsaturated molecule to make a saturated molecule

Question 5

Enthalpy of hydrogenation

Answer 5

The enthalpy change when 1 mol of an unsaturated comoound reacts with an excess of hydrogen to become fully saturated

Question 6

Whats the problems with the Kekule structure

Answer 6

• Benzene does not declourise bromine water
• All carbons - carbon bond lengths are equal
• There is only one 1,2 disubtituted product

Hydrogenation
-Benzene is less exothermic then the kekule structure therefore more stablle due to the delocailsed electron structure

Question 7

Bonding of Benzene

Answer 7

• Each C has three covalent bonds
• Spare electrons from the p orbital overlap to form the pie bond
• C-C bonds are equal in length

The delocalised structure leads to extra stability therefore the pie bonds are harder to break than a normal C-C bond

Question 8

What functional compounds take priority over armatics

Answer 8

Amines
Alcohols
Alkenes
Aldehydes
Ketones

Question 9

Why does benzene not undergo addition

Answer 9

They would lose their delocalisation and their extra stability

Question 10

Why do the elctrophiles that attack benzene need to be positivly charged

Answer 10

Benzene ring is not as electron rich as the double bond in alkenes so the electrophiles that attack must be positive

Question 11

Reagents and conditions of nitration

Answer 11

Conc nitric acid
Conc sulphuric acid - catalyst
Reflux at 50 degrees

Question 12

What can nitrobenzene be used for

Answer 12

-Explosives
-To make aromatic amines

Question 13

Reagents and conditions of acylation

Answer 13

• Acyl cholride or acid anhydride
• anhydrous aluminium chloride dissolved in dry ether
• reflux

Question 14

Reagents and conditions in the reduction of nitrobenzne to form phenylamine

Answer 14

• Sn catalyst
• XS conc HCL
  followed by
• Conc NAOH

Question 15

Whats phenylamine used for

Answer 15

Dyes

Question 16

Reactivity of benzene and methyl benzene

Answer 16

• Methyl group releases electrons - positive inductive effect
• so elctron density is higher than in benzene
• electrophilies are then more attracted