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

polymers between amino acids
(type of polyamide?)

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

ways of disposing of waste plastics

Answer 20

(burying) landfill
burning
recycling

Question 21

advantages and disadvantages of recycling plastics

Answer 21

+
reduces amount of waste going to landfill
saves raw materials (good as oil is non-renewable)
cost is lower than making plastics from scratch
produces less CO2 than burning
_
technically difficult
collecting, sorting, processing is more expensive than burning/ landfill
often cant remake the plastic you started with- have to make something else
plastics can be easily contaminated during the recycling process

Question 22

structure of amino acids?

Answer 22

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

Question 23

amino acids are amphoteric
what does it mean?

Answer 23

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 24

how to work out systematic name of amino acids

Answer 24

• 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 25

what is a zwitterion? when do they exist?

Answer 25

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 26

when does an amino acid become a zwitterion?

Answer 26

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 27

page 234

Question 28

what are proteins?

Answer 28

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

Question 29

what happens if the 2 amino acids combining are different?

Answer 29

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

Question 30

middle part of page 235

Question 31

what is primary the structure of a protein?

Answer 31

sequence of amino acids

Question 32

what is the secondary structure of a protein?

Answer 32

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

Question 33

what is the tertiary structure of a protein?

Answer 33

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 34

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

Answer 34

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 35

what is a disulphide bridge?

Answer 35

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 36

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

Answer 36

affect hydrogen bonding and formation of disulphide bonds

Question 37

what is an enzyme?

Answer 37

protein biological catalyst that increases rate of reaction by providing an alternative pathway with lower activation energy

Question 38

what is the active site part of?

Answer 38

tertiary structure

Question 39

what is stereospecificity?

Answer 39

check old book

Question 40

what is the lock and key model?

Answer 40

states that for enzyme to work, substrate has to fit in its active site if it doesn't reaction wont be catalysed

Question 41

what are inhibitors?

Answer 41

molecules with similar shape to substrate can act as an inhibitor- compete with substrate to block active site so substrate cant bind

Question 42

what does amount of inhibition depend on?

Answer 42

relative concs of inhibitor and substrate- more inhibitor= more active sites taken up so very little enzyme gets to it also affected by how strongly the inhibitor bonds to active site

Question 43

how can inhibitors be used as drugs?

Answer 43

block active sites and stop them working eg antibiotics block active site of bacteria enzyme that allows it to make cell wall- eventually burst hard to find correct drug as active site is so specific. trickier if molecule is chiral- only 1 enantiomer fits new drugs found by trial and error- takes long time- speed up by using computers to model shape of active site and predict how well drugs will interact w it

Question 44

what is DNA composed of?

Answer 44

phosphate group- ion due to - charge on one of the oxygens (see structure in text book) pentose sugar- 2-deoxyribose (see structure in text book) base- adenine, cytosine, guanine, thymine (see annotated data sheet)

Question 45

what is a polynucleotide chain?

Answer 45

nucleotides joined together by covalent bonds between phosphate group of one and sugar of another- sugar-phosphate backbone formed by condensation polymerisation- molecule of water lost

Question 46

what is the structure of DNA?

Answer 46

2 polynucleotide chains coiled into a double helix held by hydrogen bonds between bases A-T and G-C the 2 stands are complimentary

Question 47

how do hydrogen bonds occur between nucleotides?

Answer 47

between a H d+ and an lp on a nearby O, N, Fl the 2 atoms have to be the right distance apart AT form 2 H bonds, GC form 3 double helix so bases in right alignment and distance

Question 48

what is cisplatin?

Answer 48

complex of platinum (II) with 2 chloride ion ligands and 2 NH3 ligands in a square planar shape 2 chloride ions are next to each other making it cisplatin (opposite each other would be transplatin)

Question 49

how does cisplatin treat cancer?

Answer 49

prevents DNA from replicating so tumour cells stop reproducing - N atom on guanine forms coordinate bond w cisplatin's platinum ion, replacing one of its chloride ion ligands - 2nd N from nearby guanine (same or diff strand of DNA) can bond to platinum and replace 2nd chloride ion too - presence of cisplatin complex bound to DNA causes strands to kink so DNA cant unwind and be copied properly- so cant replicate properly

Question 50

what are the adverse effects of cisplatin?

Answer 50

cisplatin can bind to DNA in normal cells too problem for healthy cells that replicate frequently eg hair and blood cells so causes hair loss and suppressed immune system can also cause kidney damage

Question 51

why is cisplatin still used as chemo drug despite side effects?

Answer 51

long- term positive effects of curing cancer outweigh the negative short-term effects