6.2

Question 1

what does an ‘R’ group represent

Answer 1

alkyl chain of unspecified length

Question 2

formula, bonding, shape and bond angle of ammonia

Answer 2

NH3
covalent bonding 
hydrogen bonding (inter molecular)
107.5 bond angle 
pyramidal shape ( 3 bonded pairs and one lone pair)

Question 3

what does primary, secondary or tertiary refer to when talking about amines

Answer 3

the amount of R groups attached

primary has one r group, secondary 2, tertiary 3

Question 4

are amines (and ammonia) bases or acids? why?

Answer 4

amines and ammonia are both weak bases (by both definitions) as amines have a lone pair of electrons for donations and are a proton acceptor) –> the lone pair on the nitrogen atom can be attacked by H+ ions (proton) forming a dative covalent bond

Question 5

primary amine + acid –>

and what is special about the product

Answer 5

primary amine + acid –> ammonium salt

ammonium salts are completely nonmetal

Question 6

what reagents are required for the preparation of aliphatic amines

Answer 6

haloalkane

excess ammonia and ethanol (or excess ethanoic ammonia)

Question 7

what mechanism is used to make aliphatic amines

Answer 7

nucleophilic substitution of haloalkanes

Question 8

what are the two steps in the preparation of aliphatic amines

Answer 8

1) react a haloalkane with ammonia to make a salt
(CH3CH2Br + NH3 –> [CH3CH2NH3]+Br-)
2) add excess ammonia to form an amine + ammonium
salt
( [CH3CH2NH3]+Br- + NH3 –> CH3CH2NH2 + NH4+Br-)

Question 9

why is ammonia added in excess in the preparation of aliphatic amines

Answer 9

otherwise additional substitutions of the hydrogen atoms will occur making secondary and tertiary amines

Question 10

why is the preparation of aliphatic amines done in a sealed container

Answer 10

because ammonia is very volatile and if the container wasn’t sealed it would be lost from the system.

Question 11

what are the reagents and conditions in the preparation of aromatic amines

Answer 11

nitroarene (benzene with a NO2 group)
tin + conc. hydroclorc acid as a reducing agent
(sodium hydroxide- strong alkali) added after 30mins to neutralise any excess acid
conditions: 100C under reflux

Question 12

what is an α-amino acid

Answer 12

an amino acid which the -COOH and the -NH2 functional groups are added to the same carbon

Question 13

what two functional groups do α-amino acids have

Answer 13

carboxylic acid -COOH

amine group -NH2

Question 14

general formula for α-amino acids

Answer 14

RCH(NH2)COOH

Question 15

why are amino acids considered amphoteric

Answer 15

because the carboxylic acid functional group acts as a weak acid that will partially ionise in water
AND the amine group acts as a base due to the lone pair on the nitrogen atom

Question 16

how can α-amino acids form zwitterions

Answer 16

becasue the two functional group groups exchange a proton and make an internal salt
COO- and NH3+ (charges cancel out)

Question 17

what is the isoelectric point

Answer 17

is when there is no overall electrical charge due to each zwitterion having an internal balance

Question 18

how will changing the pH have an effect on the charge of the ion

Answer 18

a lower pH (1) than the isoelectric point will make a postive ion (NH3+)
a higher pH (13) than the isoelectric point will make a negative ion (COO-)

Question 19

what is an amide functional group

Answer 19

-C(=O)N(-H)

Question 20

what do amino acids form when they react together

Answer 20

amino acids form a peptide in condensation reactions

Question 21

what is the reverse of condensation reactions called

Answer 21

hydrolysis

when polypeptides/proteins are hydrolyses into separate amino acids

Question 22

how can amides be made

Answer 22

• condensation of amino acids

- by mixing acyl chloride with ammonia

Question 23

what are optical isomers

Answer 23

non-superimposable images of each other
same structure but are mirror images of each other
these molecules are entantiomers to each other (different entantiomers rotate plane polarized light in opposite directions)

Question 24

what is a chiral molecule

Answer 24

a molecule with no plane of symmetry

Question 25

what is a chiral carbon

Answer 25

a carbon with 4 different atoms or groups attached

Question 26

what is a racemate or racemic mixture

Answer 26

a 50:50 mixture of each entantiomers. race mate mixtures have no effect on plane polarized light