Module 1 - Rings, Acids, Amines

Question 1

Describe the structure of benzene according to delocalised model

Answer 1

P orbitals overlap above and below the plane creating pi bonds.
All bonds are the same length

Question 2

Explain how information on the bond lengths in benzene provides support for the delocalised model

Answer 2

X-Ray’s show that all the bonds are the same length (discrediting Kekules structure)

Question 3

What are aromatic compounds

Answer 3

Compounds that contain a benzene ring

Question 4

Explains why alkenes will react via addition reactions at room temp but benzene won’t

Answer 4

In alkenes Carbon double bond is a localised high area of high electron density.
Delocalised electrons makes benzene very stable and unwilling to undergo addition reactions which would destroy stability

Question 5

Explain why electrophiles are attracted to aromatic compounds

Answer 5

Aromatic compounds contain a benzene ring, which is a region of high electron density.
Electrophiles are electron deficient so are attracted to these regions

Question 6

Give two examples of halogen carriers

Answer 6

AlCl3

Fe

Question 7

Explain why halogen carriers are needed for benzene to react with bromine

Answer 7

Bromine not strong enough to react with the benzene ring on its own

Question 8

What gas is evolved when phenol reacts with sodium metal

Answer 8

Hydrogen gas

Question 9

Explain why phenol will react with bromine water but benzene won’t

Answer 9

Benzene the p orbital electrons are delocalised. This makes benzene very stable so it is unwilling to undergo addition reactions with halogens.
In phenols one lone pair of electrons in oxygen increases electron density of the ring.
This higher electron density means that phenol can polarise bromine and cause a reaction

Question 10

Give two uses of phenols

Answer 10

Antiseptics/production of polymers/manufacture of resins

Question 11

What is the difference between an aldehyde and a ketone

Answer 11

Aldehyde have carbonyl group at the end of the carbon chain, ketones have is in the middle

Question 12

Describe the colour change that would be seen if ethanol was oxidised to ethanal using acidified potassium dichromate

Answer 12

Orange to green

Question 13

Name a reducing agent which could be used to reduce an aldehyde to a primary alcohol

Answer 13

NaBH4

Question 14

Name the reaction mechanism that takes place when ketones are reduced to alcohols

Answer 14

Nucleophilic addition

Question 15

What does Brady’s reagent test for

Answer 15

Carbonyl groups

Question 16

Describe how you could use Brady’s reagent and melting point data to determine the identity of an unknown compound

Answer 16

carbonyl compounds produces a crystalline compound with different melting points.
Purify crystals
Find their me,ting points and compare it against known melting points

Question 17

What is tollens’ reagent

Answer 17

A solution of silver nitrate dissolved in aqueous ammonia

Question 18

Describe what you would observe if a carboxylic acid reacted with magnesium metal

Answer 18

A gas

Question 19

What two products are produced when an ester is broken down by acid hydrolysis

Answer 19

Carboxylic acid and alcohol

Question 20

What two products are produced when an ester is broken down by base hydrolysis

Answer 20

Carboxylate ion and alcohol

Question 21

Give two common uses of esters

Answer 21

Perfumes/flavouring food/adding scents to products

Question 22

What is n unsaturated fatty acid

Answer 22

Carboxylic acid with a long hydrocarbon chain that contains one or more carbon-carbon double bonds

Question 23

What two reactants do you need to produce a triester

Answer 23

Glycerol and fatty acids

Question 24

What is cholesterol

Answer 24

Soft waxy material found in cell membranes and transported in your blood steam

Question 25

How is biodiesel made

Answer 25

Reacting triglycerides with methanol

Question 26

Why can amines act as bases

Answer 26

They can form a dative bond with H ion

Question 27

How can an amine be produced from a haloalkane

Answer 27

Heating haloalkane with excess ethanolic ammonia

Question 28

Explain why a mixture of primary, secondary, tertiary and quaternary amines are produced in these reactions

Answer 28

More than one hydrogen can be subbed on the ammonia

Question 29

What are azo dyes

Answer 29

Man made dyes containing azo group (N double bond N)

Question 30

Explain why presence of benzene rings in azo dyes can lead to a very stable structure

Answer 30

Azo group becomes part of delocalised electron system which stabilises compound

Question 31

Give two uses of azo dyes

Answer 31

Food colourings/ indicators / paint pigment

Question 32

Describe Kekules model for the structure of benzene.

Answer 32

A ring of six carbons joined together by alternating double and single c-c bonds.
Later adapted it to structure flipping between two isomers