3.7 polymers

Question 1

what is condensation polymerisation?

Answer 1

• usually involves 2 diff monomers
• each monomer has at least 2 functional groups
• each functional group reacts w another to form a link, forming polymer chains
• each time a link is formed, a molecule of H2O is lost

Question 2

examples of condensation polymers

Answer 2

polyamides (amide links -CONH-)
polyesters (ester link -COO-)
polypeptides (amide links -CONH- called peptide bonds)

Question 3

what reacts to make polyamides?

Answer 3

dicarboxylic acids and diamines
carboxyl group reacts w amino group to form amide links and H2O is lost

Question 4

which polyamides do you need to know?

Answer 4

nylon 6,6
kevlar
(learn structures)

Question 5

what is nylon 6,6 formed from?
properties/ uses?

Answer 5

hexanedioic acid and 1,6-diaminohexane

strong and resistant so used for clothing, carpet, rope, airbags, parachutes

Question 6

what is kevlar formed from?
properties/uses

Answer 6

benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene

light and strong so used in bulletproof vests, boat construction, car tyres, lightweight sports equipment

Question 7

what are peptides?

Answer 7

amino acids contain amine functional group and carboxylic acid functional group
they react to form polyamides
polymers between amino acids are more commonly called peptides

Question 8

what reacts together to form polyesters?

Answer 8

carboxyl groups of dicarboxylic acids and hydroxyl groups of diols
they form ester links

Question 9

what are polymers joined by ester links called?

Answer 9

polyesters

Question 10

what is the polyester that you need to know?
what is it formed from?
properties/uses

Answer 10

terylene (PET)
benzene-1,4-dicarboxylic acid and ethane-1,2-diol
some forms stable at cold and hot temps so useful for creating containers for ready meals. other forms used for plastic bottles, clothes, sheets, sails

Question 11

what is hydrolysis?
what are the products?

Answer 11

breaking ester/amide links by adding water molecules back in
the products are the monomers used to make the polymer

Question 12

how is hydrolysis done in the lab?

Answer 12

too slow with water so polyamides hydrolysed with acid and polyesters with alkalis

Question 13

are condensation or addition polymers stronger?
why?

Answer 13

condensation
made up of chains containing polar bonds (C=O, C-N, C-O). so, they have permanent dipole-dipole and hydrogen bonds between chains as well as induced dipole-dipole

Question 14

steps of working out repeating unit of polyamide formed when diamine and dicarboxylic acid react

Answer 14

• draw the 2 monomers next to each other
• remove an OH from the dicarboxylic acid and a H from one of the N in the diamine
• join C=O and N together to make an amide link
• take a H off other nitrogen and OH off the other COOH at the ends of the molecules and draw the trailing bonds

Question 15

how to find repeating unit from longer section of polyester/ polyamide chain

Answer 15

• look along chain and find repeating pattern
• repeating unit should have C=O from ester/amide link at one end and -O- or -NH- part of link at other

Question 16

how to identify monomers that formed particular condensation polymer

Answer 16

• if given part of polymer chain, first find repeating unit
• remove bond in middle of central amide/ester link (bond between -C=O and -NH in polyamides or -C=O and O in polyesters)
• add OH onto -C=O to make carboxyl groups
• for polyamides, add H onto NH to make NH2
• for polyesters, add H onto O to make OH group and OH to any terminal carbons

Question 17

not all condensation polymers are made from dicarboxylic acid and diamine or diol. why?

Answer 17

if a molecule contains carboxylic acid and alcohol/ amine group, it can polymerise with itself to form a condensation polymer with only one monomer
eg with amino acids

molecules that contain both amine and alcohol group can react w dicarboxylic acids to form polymer w both amide and ester links

Question 18

biodegradability of polymers

Answer 18

polyalkenes are inert as bonds between repeating units are non-polar so arent susceptible to nucleophile attack- good for use but means theyre non-biodegradable

condensation polymers eg PET and nylon can be hydrolysed as bonds are polar so can be attacked by nucleophiles so they are biodegradable

Question 19

options to dispose of waste plastics

Answer 19

bury, burn, sort for reuse/recycling

Question 20

page 229

Question 21

structure of amino acids?

Answer 21

2 functional groups NH2 and COOH
structure is all the same apart from R groups
H2N-CH(R)-COOH
chiral molecule

Question 22

amino acids are amphoteric
what does it mean?

Answer 22

they have acidic and basic properties
can act as acids due to COOH- can donate proton
can act as bases due to NH2- can accept a proton

Question 23

how to work out systematic name of amino acids

Answer 23

• find longest chain that includes COOH and write down name
• number the Cs starting w the 1 in COOH as 1
• write down position of any NH2 groups as amino
• write down names of other functional groups and number them

Question 24

what is a zwitterion?
when do they exist?

Answer 24

a dipolar ion- has both + and - change in diff parts of the molecule

exist at an amino acids isoelectric point (pH where overall charge is 0- diff for diff amino acids but around 7)

Question 25

when does an amino acid become a zwitterion?

Answer 25

when amino group protonated to NH3+ and COOH is deprotonated to COO-
- in acidic conditions, NH2 more likely to be protonated but COOH unchanged so + charge
- in basic conditions, COOH more likely to be deprotonated but NH2 unchanged so - charge
- only on/near isoelectric point will both groups be ionised

Question 26

page 234

Question 27

what are proteins?

Answer 27

condensation polymers of amino acids- amino acids joined by peptide links

Question 28

what happens if the 2 amino acids combining are different?

Answer 28

2 diff dipeptides form as amino acids can join either way around

Question 29

middle part of page 235

Question 30

what is primary the structure of a protein?

Answer 30

sequence of amino acids

Question 31

what is the secondary structure of a protein?

Answer 31

peptide links can form hydrogen bonds with each other meaning the chain isnt straight
forms alpha-helix or beta-pleated sheet

Question 32

what is the tertiary structure of a protein?

Answer 32

chain of amino acids is coiled and folded in a characteristic way. extra bonds form between diff parts of polypeptide chain making protein a 3D shape

covalent bonds, ionic bonds, disulphide bridges

Question 33

what do hydrogen bonds do in a protein?
how do they exist?

Answer 33

holds protein shape
occurs between polar groups such as OH and NH2
these groups contain electronegative atoms which induce a d+ charge on the H atoms
the H is then attracted to lp of electrons on adjacent polar groups and a H bond is formed

Question 34

what is a disulphide bridge?

Answer 34

amino acid that is part of a protein is called a residue
disulphide bonding occurs between residues of amino acid cysteine
cysteine contains -SH (thiol) group that can lose its H atom and join together to form a disulphide-S-S- bond w another thiol group
these disulphide bonds link together diff parts of protein chain and help them stabilise tertiary structure

Question 35

how do factors such as temp and pH affect shape of protein?

Answer 35

affect hydrogen bonding and formation of disulphide bonds