benzene

Question 1

What is benzene

Answer 1

C6H6

Question 2

Properties of benzene

Answer 2

Highly flammable
Sweet-smelling
Found naturally in crude oil
A carcinogen

Question 3

Is benzene reactive or unreactive

Answer 3

unreactive

Question 4

What are arenes

Answer 4

hydrocarbons based on benzene

Question 5

similarities between Kekule and delocalised model

Answer 5

• overlap of p orbitals

- Pi bond above and below

Question 6

diffrences beterrn kekule and delocalised model

Answer 6

• kekuke has alternating pi bonds,localised electrons

- delocalised pi electrons spread around ring

Question 7

3 pieces of evidence supporting delocalised model of benzene

Answer 7

• bond length is not single of double bond length
• Hydrogenation is less exothermic than expected
• benzene does not react with bromine

Question 8

-OH with benzene ring name

Answer 8

phenol

Question 9

-NH2 with benzene ring name

Answer 9

phenylamine

Question 10

why is it harder for benzene to react with bromine

Answer 10

The delocalised electrons above and below the plane are very stable.

• spread out the negative charge
• addition reaction would break ring

Question 11

what can a halogen carrier be used to do

Answer 11

add a halogen atom onto the benzene ring

Question 12

Types of halogen carrier

Answer 12

AlCl3 or FeBr3

Question 13

What are acyl chlorides

Answer 13

like COOH but OH replaced by Cl

Question 14

Why is phenol less soluble than water

Answer 14

presence of a non polar benzene ring

Question 15

What type of acid is a phenol

Answer 15

Weak acid

Question 16

alcohols, phenol, carboxylic acid acidity from least to most

Answer 16

Alcohol,phenol,carboxilyic acid

Question 17

How can you show phenol is a weak acid

Answer 17

Reacts with strong base (NAOH), doesnt react with carbonates

Question 18

How to distinguish between a phenol and carboxylic acid

Answer 18

React with sodium carbonate, carboxilyic acid will make CO2

Question 19

What does phenol and bromine make

Answer 19

2,4,6 tribromophenol and HBR

Question 20

What does the nitration of phenol produce

Answer 20

2 and 4 nitro phenol and water

Question 21

Why are phenols more reactive than benzene

Answer 21

lone pair of electrons from the oxygen p-orbital donated to the pi system of the phenol. Increases electron density, attracts electrophiles more strongly

Question 22

What directing group is the -NH2 group

Answer 22

2 or 4

Question 23

What directing group is the -NO2 group

Answer 23

3

Question 24

What is the alkylation of benzene

Answer 24

sub of a hydrogen atom to an alkyl

Question 25

Why are all carbon carbon bonds the same length in a benzene

Answer 25

Each carbon atom forms single covalent bonds to the carbon on either side
All the carbon carbon bond lengths r the same

Question 26

How do rings form around benzene

Answer 26

Unpaired electron on each carbon atom is in a p orbital that sticks out above and below the plane
The p orbitals on each carbon atom combine to form a ring of delocalised electrons

Question 27

What does a lower enthalpy change for benzene mean

Answer 27

More energy needed to break the bond than the other so less reactive

Question 28

When is phenyl used to name benzene

Answer 28

attached to an alkyl chain with a functional group or 7 or more carbon atoms

Question 29

COOH attached to a benzene name

Answer 29

benzoic acid

Question 30

CHO attached to benzene name

Answer 30

benzaldehyde

Question 31

A student adds bromine water to a solution of phenol.

What would the student see during this reaction?

Answer 31

Bromine water goes from orange to colourless and a white precipitate is formed.

Question 32

What is the number of sigma bonds in a benzene molecule?

Answer 32

12

Question 33

Difference between Kekule and delocalised in terms if a pi bond

Answer 33

Kekule - 3 pi bonds with 2 electrons localised

-delocalised - 1 pi ring with 6 electrons