past mistakes paper 2 only

Question 1

what is a nucleophile?

Answer 1

electron pair donor

Question 2

what is an electrophile?

Answer 2

electron pair acceptor

Question 3

electrophilic addition

mechanisms we need to know

Answer 3

• alkenes + halogens/ hydrogen halides

Question 4

electrophilic substitution

mechanisms we need to know

Answer 4

• halogenation of benzene
• nitration of benzene

Question 5

nucleophilic addition

mechanisms we need to know

Answer 5

• carbonyl and KCN
• reduction of carbonyls

Question 6

nucleophilic substitution

mechanisms we need to know

Answer 6

• haloalkanes + NaOH

Question 7

is pi bond or sigma bond stronger?

and how does this relate to reactivity of alkenes

Answer 7

• sigma bond is stronger than pi bond
• alkenes are more reactive than alkanes
• due to the presence of the pi bond which is weaker than sigma bond
• making it more susceptible to breaking and reacting with other molecules

Question 8

what are calibration curves used for in gas chromatography?

Answer 8

• confirm the concentration of components in a mixture

Question 9

explain the relative resistance to chlorination of benzene compared to alkanes

Answer 9

• benzene contains delocalised electrons
• alkenes contain localised electrons
• benzene has a lower electron density and therefore
• induces a weaker dipole on chlorine molecule- or doesn’t polarise the electrophile enough

Question 10

what do you react an amine with to form an amide?

Answer 10

• acyl chlorides
• can’t react with carboxylic acids, due to basicity of amines- forms a carboxylate salt instead

Question 11

why is a polymer with an ester link biodegradeable?

Answer 11

• can be hydrolysed- ester link broken

Question 12

what do you react a carboxylic acid with to form an acyl chloride?

Answer 12

• SOCl2

Question 13

heterolytic fission

definition

Answer 13

• one bonded atom receives both electrons from the bonded pair
• breaking of a covalent bond

Question 14

homolytic fission

definition

Answer 14

• each bonding atom receives one electron from the bonded pair, forming two radicals
• breaking of a covalent bond

Question 15

what is the solvent used in NMR?

Answer 15

• CDCl3

Question 16

more strongly adsorbed onto the stationary phase?

Answer 16

• moves less up the TLC plate
• smaller Rf value

Question 17

equations for ozone

Answer 17

1. CF₂Cl ₂–> CF₂Cl + Cl
2. Cl* + O₃ –> ClO* +O₂
3. ClO* + O –> Cl* + O₂

Question 18

optical isomerism

definition

Answer 18

• molecules that are non-superimposable mirror images of each other about a chiral carbon