3.7 polymers Flashcards
what is condensation polymerisation?
- 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
examples of condensation polymers
polyamides (amide links -CONH-)
polyesters (ester link -COO-)
polypeptides (amide links -CONH- called peptide bonds)
what reacts to make polyamides?
dicarboxylic acids and diamines
carboxyl group reacts w amino group to form amide links and H2O is lost
which polyamides do you need to know?
nylon 6,6
kevlar
(learn structures)
what is nylon 6,6 formed from?
properties/ uses?
hexanedioic acid and 1,6-diaminohexane
strong and resistant so used for clothing, carpet, rope, airbags, parachutes
what is kevlar formed from?
properties/uses
benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene
light and strong so used in bulletproof vests, boat construction, car tyres, lightweight sports equipment
what are peptides?
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
what reacts together to form polyesters?
carboxyl groups of dicarboxylic acids and hydroxyl groups of diols
they form ester links
what are polymers joined by ester links called?
polyesters
what is the polyester that you need to know?
what is it formed from?
properties/uses
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
what is hydrolysis?
what are the products?
breaking ester/amide links by adding water molecules back in
the products are the monomers used to make the polymer
how is hydrolysis done in the lab?
too slow with water so polyamides hydrolysed with acid and polyesters with alkalis
are condensation or addition polymers stronger?
why?
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
steps of working out repeating unit of polyamide formed when diamine and dicarboxylic acid react
- 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
how to find repeating unit from longer section of polyester/ polyamide chain
- 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
how to identify monomers that formed particular condensation polymer
- 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
not all condensation polymers are made from dicarboxylic acid and diamine or diol. why?
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
biodegradability of polymers
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
options to dispose of waste plastics
bury, burn, sort for reuse/recycling
page 229
structure of amino acids?
2 functional groups NH2 and COOH
structure is all the same apart from R groups
H2N-CH(R)-COOH
chiral molecule
amino acids are amphoteric
what does it mean?
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
how to work out systematic name of amino acids
- 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
what is a zwitterion?
when do they exist?
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)
when does an amino acid become a zwitterion?
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
page 234
what are proteins?
condensation polymers of amino acids- amino acids joined by peptide links
what happens if the 2 amino acids combining are different?
2 diff dipeptides form as amino acids can join either way around
middle part of page 235
what is primary the structure of a protein?
sequence of amino acids
what is the secondary structure of a protein?
peptide links can form hydrogen bonds with each other meaning the chain isnt straight
forms alpha-helix or beta-pleated sheet
what is the tertiary structure of a protein?
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
what do hydrogen bonds do in a protein?
how do they exist?
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
what is a disulphide bridge?
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
how do factors such as temp and pH affect shape of protein?
affect hydrogen bonding and formation of disulphide bonds
what is an enzyme?
protein
biological catalyst that increases rate of reaction by providing an alternative pathway with lower activation energy
what is the active site part of?
tertiary structure
what is stereospecificity?
check old book
what is the lock and key model?
states that for enzyme to work, substrate has to fit in its active site
if it doesn’t reaction wont be catalysed
what are inhibitors?
molecules with similar shape to substrate can act as an inhibitor- compete with substrate to block active site so substrate cant bind
what does amount of inhibition depend on?
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
how can inhibitors be used as drugs?
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
what is DNA composed of?
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)
what is a polynucleotide chain?
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
what is the structure of DNA?
2 polynucleotide chains coiled into a double helix held by hydrogen bonds between bases
A-T and G-C
the 2 stands are complimentary
how do hydrogen bonds occur between nucleotides?
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
what is cisplatin?
complex of platinum (II) with 2 chloride ion ligands in a square planar shape
2 chloride ions are next to each other making it cisplatin (opposite each other would be transplatin)
how does cisplatin treat cancer?
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 ) ligands replacement reaction)
- 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
what are the adverse effects of cisplatin?
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
why is cisplatin still used as chemo drug despite side effects?
long- term positive effects of curing cancer outweigh the negative short-term effects
