Amines, Amino Acids and Polymers

Question 1

preparation of aliphatic amines

Answer 1

substitution of halogen alkanes with excess ethanolic ammonia (add aqueous alkali)

Question 2

what type of substitution of the preparation of aliphatic amines

Answer 2

nucleophillic, as the ammonia has a lone pair of electrons on the nitrogen atom, allowing substitution to occur with a haloalkane

Question 3

why is ammonia in excess in the preparation of aliphatic amines

Answer 3

reduces further substitution of the amine to form secondary/tertiary amines

Question 4

ammonia is very soluble in water, so why is ethanol used as a solvent and not water in the preparation of aliphatic amines

Answer 4

prevents any substitution of the haloalkane by water to form alcohols

Question 5

preparation of aromatic amines

Answer 5

reduction of nitroarenes using tin and concentrated HCL (add aqueous alkali)

Question 6

what conditions is the preparation of aromatic amines carried out under

Answer 6

nitrobenzene heated under reflux with Tin and conc HCL forming phenylammonium chloride, which is then reacted with excess NaOH to produce the aromatic amine, phenylamine. Tin and HCL act as reducing agent

Question 7

what is an amine

Answer 7

ammonia molecule with 1 or more H atoms replaced with a carbon ring or chain

Question 8

how do you classify amines

Answer 8

by the number of H substituted

primary, secondary, tertiary

Question 9

what are N-substituted amines

Answer 9

when there are 2 or more different groups attached to the Nitrogen
eg. N-butylethylamine or 3-amino pentane

Question 10

what do amines smell like

Answer 10

fish

Question 11

reactions of amines
CH3CH2NH2 + HCL–>
CH3CH2CH2CH2NH2 + HNO3 –>

Answer 11

CH3CH2NH3+ + Cl-
CH3CH2CH2CH2NH3+ + NO3-
dative covalent bond between hydrogen atom and nitrogen

Question 12

why are amines basic

Answer 12

have a lone pair of electrons so they are able to accept H+ ions from acids

Question 13

most basic to least out of-

propylamine/aminopropane, ammonia and phenylamine

Answer 13

propylamine- positive inductive effect pushes electrons
ammonia
phenylamine- lone pair electrons donated into delocalised ring

Question 14

what is an alpha amino acid

Answer 14

carbon attached to amino group is also attached to carboxylic group

Question 15

what does amphoteric mean

Answer 15

can act as an acid or a base

Question 16

what is a zwitterion

has high melting point due to electrostatic attraction

Answer 16

has intermediate values of pH (not always neutral)
is both positive and negative
RCH – (NH3+) – COO-

Question 17

what is the isoelectric point

Answer 17

concentration of zwitterion that is highest

Question 18

What happens when an amino acid is in an acidified solution

Answer 18

adds a hydrogen to the nh2 group

RCH – (NH3+) – COOH

Question 19

what happens when an amino acid is in an alkaline solution

Answer 19

removes hydrogen from OH group

RCH – (NH2) – COO-

Question 20

general formula for an amino acid

Answer 20

RCH(NH2)COOH

Question 21

what are amides and what bond is present

Answer 21

R – CO – NH

peptide bond

Question 22

preparation of an amide

Answer 22

acyl chloride + ammonia –> primary amide (primary substitution)
acyl chloride + primary amide –> secondary amide (secondary substitution)

Question 23

how does cis trans isomerism arise in ….

Answer 23

double bond present between 2 carbons so can’t rotate
hydrogens present on both sides
2 different groups on each carbon

Question 24

define structural isomerism

eg. chain, positional, functional group

Answer 24

same molecular formula but different structural formula

Question 25

define stereoisomerism

eg. E/Z, optical

Answer 25

same structural formula but different arrangement in space

Question 26

what causes steroeisomerism

Answer 26

a carbon with 4 different groups attached
chiral centre
mirror images are non-superimposable

Question 27

what is optical steroisomerism

Answer 27

non-superimposable mirror images about a chiral centre

Question 28

what is an enantiomer

Answer 28

pair of optical isomers

Question 29

how do optical isomers differ

Answer 29

differ in chemical reactions
the isomers rotate plane polarised light in opposite directions- causing a difference in properties of the mirror image forms of a chiral compound

Question 30

why is chirality important

Answer 30

biological receptors will only accept one enantiomers

Question 31

can amino acids be switched around in tripeptides to form a different compound

Answer 31

yes

Question 32

how can tripeptides be analysed using gas chromatography, coupled with mass spectroscopy

Answer 32

gas chromatography separates peptides
mass spectroscopy will fragment peptides
using a database compare the mass ion calculated

Question 33

out of 2 polymers, one containing a C=O as well as being an ester, and one without, which is likely to be degradable

Answer 33

the one with a C=O present and the ester, as the bond absorbs radiation
and the ester linkage can be hydrolysed

Question 34

what is it called when multiple monomers join together

Answer 34

polymerisation

Question 35

benefits of polymers

Answer 35

can replace natural materials
cheaper
better suited to a particular use

Question 36

negatives of polymers

Answer 36

non-biodegradable

Question 37

alternatives to landfill for polymers

Answer 37

burning for energy- scrubbers needed to neutralise acidic gases
feedstock (make other chemicals)
recycling

Question 38

difference between condensation polymers and addition polymers

Answer 38

condensation- polyamides eg. kevlar, nylon 6-6

addition- end in ene, 100% atom economy, need high pressure and temp

Question 39

how are polyamides/polyesters hydrolysed

Answer 39

in alkaline or acidic conditions
should theoretically can be biodegradable but takes a
very long time in reality