Polymers and Life Flashcards
carboxylic acid + carbonate
–> carbon dioxide and water
fizzing due to co2 production
acid-base, carbonate ion is the base
carboxylic acid + carbonates
carbon dioxide + water
Fizzing due to carbon dioxide production
Acid base reaction, carbonate ion is the base because it accepts protons
phenols and alcohols react with carbonates
they don’t have a great enough concentration of hydrogen ions to react with carboxylic acids in the same way as carbonates, so there will be no fizzing when they react.
carboxylic acids; phenols and alcohols react with metals
they all form salts in a redox reaction with metals
carboxylic acids, phenols and alcohols react with strong bases
Carboxylic acids and phenols are strong enough acids to react with strong bases to form salts, alcohols are not.
how are esters formed
an alcohol reacts with a carboxylic acid.
Occurs slowly unless there is an acid catalyst (conc HCl or conc H2SO4) and the reagents are heated under reflux.
The reaction is a condensation reaction
where is the ester link formed
by the condensation reaction of the hydroxyl group of the alcohol and the carboxyl group in the acid, in esterification
reverse reaction of estérification
ester hydrolysis
characteristics of esters
good solvents, strong sweet smells, used in food flavourings
how can you improve yield of an ester from a given amount of acid
add an excess of alcohol or distill the water off as it forms which the sulfuric acid catalyst can absorb some of. This helps shift the POE right
esterifying with phenols
the -oh group is less reactive in phenols in esterification than the -oh of ethanol so it needs a more vigorous reagent to esterify it e.g an acid anhydride
what happens in condensation polymerisation
the monomers must have at least two suitable functional groups per molecule and they join together to give a polymer and a small stable molecule
what happens in addition polymerisation
the monomers join together to form a polymer molecule ONLY
primary, secondary + tertiary amines
Primary amine = amines with one alkyl group, two hydrogens
Secondary amine = amines with two alkyl groups, one hydrogen
Tertiary amine = amines with three alkyl groups, no hydrogens
diamines
amines used to make condensation polymers have two amine groups attached
amines with low Mr
low relative molecular masses are gases/volatile liquids
bonds in an amine
In the nitrogen atom of an amine, 3 pairs of electrons form localised covalent bonds while the other two electrons form a lone pair.
The LPE is responsible for amines acting as bases because it can take part in dative covalent bonding and being soluble in water
amines with small alkyl groups
soluble because the strong attraction between the amine and water is strong enough to break the H bonds
why are amines with larger alkyl groups insoluble in water
the groups are unable to break the H bonds between water so the enthalpy change to break the H bonds is greater than that of formation of IM bonds so formation of solution is less energetically feasible
amide formation of acyl chloride with acids
The h3o+ ions in acid are more powerful proton donors than water
They react to form an ammonium ion and water, the solution loses its strong amine smell
ethanoyl chloride + NH3 → primary amide + HCl
primary amides
have 1 alkyl group and two hydrogens, they are derived from carboxylic acids by replacing the -OH with -NH2
amines react with acyl chlorides
CH3COCl + RNH2 → CH3CONHR + HCl - a condensation reaction producing a secondary amide
features of polyamides
Formed by diamines and dicarboxylic acids because they have reactive groups in two places in their molecules. This is a condensation polymerisation.
Polyamides = nylons which are named from the number of carbons, the first digit is the number in the diamine and the second is those in the -COOH
reactions of acyl chlorides
Acyl chloride + amine → amide + HCl
Acyl chloride + alcohol → ester + HCl
hydrolysis of water
Ester + water → carboxylic acid + alcohol (catalyst + excess water)
alkaline hydrolysis of esters
Ester + OH- → carboxylate salt + alcohol
why is reflux used
to control temperature, to ensure reactants + products do not escape, and to make rate constant.m
primary and secondary amide hydrolysis
Primary amide in acidic conditions with water forms a carboxylic acid and the ammonia accepts a H+ from the acid to form an ammonium ion
Secondary amide in similar conditions forms an amine salt instead of an ammonium ion
CH3CONHCH3 + H2O + H+ → CH3COOH + CH3NH3+
alkaline hydrolysis
Amide heated with mod conc alkali like NaOH
Secondary amide forms a carboxylate ion and the amine
E.g CH3CONHR + OH- → CH3COO- + RNH2
The -COOH donates a H+ to form the carboxylate ion
z witter ions
particles containing both positively + negatively charged groups with no overall electric charge
Zwitterions form when the two FGs in an amino acid interact
how do zwitter ions form
The NH2 becomes NH3+ by receiving a H+ from the -COOH. The COOH becomes COO- by donating a H+ to the NH2
why are amino acids soluble
due to ion-dipole interactions. They are neutral in this solution unless there is an extra one of the FGs
how do amino acids buffer the effect of acids
H3O+ + H3N+-CHRCOO- → H2O + H3N+-CHRCOOH (-COO picks up a hydrogen ion)
amino acids in acid solution
H3N+-CHRCOOH
amino acids in alkaline
H2N-CHRCOO-
amino acids in neutral solution
H3N+-CHRCOO-
mirror images of isomers are
non-superimposable because they cannot superimpose without breaking bonds and moving around chemical groups. This would correspond to a chemical reaction in such a way that it is turned into a new compound, they are therefore isomers
what is a chiral centre
the carbon atom is bonded to 4 different groups.
enantiomers
behave identically on ordinary chemical reactions but can behave differently in presence of other chiral molecules. Most physical properties are the same but may smell/taste different
making peptides/proteins
two amino acids join to form a dipeptide in a CR, the secondary amide (CONH) group formed is a peptide link.
Peptides are secondary amides that can be hydrolysed with mod conc HCl to hydrolyze the C-N amide bond
acid hydrolysis of proteins
Dipeptide + water + 2H+ → two amino acids
