Unit 4 Extra

Question 1

Name the mechanism of the nitration of benzene

Answer 1

Electrophilic substitution

Question 2

What allows 2,4-DNPH to react as a base

Answer 2

The lone pair of electrons on the N atoms

Question 3

What is seen when 2,4-DNPH is used to identify an aldehyde or ketone

Answer 3

Orange/red solid

Question 4

Why is 2,4-DNPH an appropriate reagent to use for identification of aldehydes and ketones

Answer 4

The derivatives formed have a precise melting temperature for identification

Question 5

Recrystallisation

Answer 5

• dissolve impure solid in a minimum volume of hot solvent in a water bath
• allow to cool and then filter it off and dry

Question 6

Now is nitric (III) acid prepared

Answer 6

Sodium nitrate (III) and HCl

Question 7

Reagents used for iodoform test

Answer 7

NaOH/I2

Question 8

Why would an amino acid be insoluble in methanol

Answer 8

It exists as a zwitterion and ionic compound are not generally soluble in covalent solvents

Question 9

How does condensation polymerisation differ from addition polymerisation

Answer 9

Condensation polymerisation- a small molecule is eliminated
Addition polymerisation- no elimination

Question 10

What other than carbonyls can decolourise acidified potassium manganate (VII)

Answer 10

Alkenes

Question 11

Catalyst that can be used for hydrogenation of alkenes

Answer 11

Nickel

Question 12

What is meant by the term radical

Answer 12

A species with an unpaired electron

Question 13

State the type of mechanism occurring when bromine is added across the double bonds of an alkene

Answer 13

Electrophilic addition

Question 14

Why is the melting temperature of an amino acid melting temperature much higher than other molecules of a similar size

Answer 14

They exist as zwitterions and so has strong ionic character therefore much stronger forces between molecules

Question 15

Mechanism occurring in nitration of benzene

Answer 15

Electrophilic substitution

Question 16

Equation that binds frequency and wavelength

Answer 16

c=fgamma

Question 17

Equation that bind energy and frequency

Answer 17

E=hf

Question 18

Why is something colourless in terms of the electromagnetic spectrum

Answer 18

It does not absorb in the visible region

Question 19

What colour has the shortest wavelength in the visible spectrum

Answer 19

Violet

Question 20

Which colour has the longest frequency in the visible spectrum

Answer 20

Red

Question 21

Reagents necessary to produce an amine from a nitrate

Answer 21

Tin and concentrated hydrochloric acid

Question 22

Differences between condensation polymerisation and addition polymerisation

Answer 22

• in condensation polymerisation a small molecule is eliminated, this does not occur with addition polymerisation

Question 23

What are stereoisomers

Answer 23

Isomers with the same structural formula but biffer in the way the bonds are arranged in space

Question 24

Why can E-Z isomerism occur

Answer 24

There is no rotation about a double bond

Question 25

Evidence for delocalised structure of benzene

Answer 25

• all bonds same length
• enthalpy of hydrogenation means benzene is more stable than suggested by kekule structure
• benzene tends to react by substitution not addition