Section 8 Polymers And Life Flashcards
(18 cards)
Amino acids as zwitterions?
Zwitterion is overall neutral molecule that has both positive and negative charge in different parts of the molecule. An amino acid can only act act as zwitterion at its isoelectric point the pH where overall charge = 0.
How cam paper chromatography be used to identify unknown amino acids?
- Draw pencil line near bottom of chromatography paper and put a concentrated spot of the mixture you want to investigate on it.
- Place paper into a beaker containing a small amount of solvent so that the solvent level is below the spot. Place a watch glass on top to stop solvent evaporating
- Diff chemicals move at diff rates so separate out
- When solvent nears top, mark solvent front with a pencil
- Dip paper into a jar containing a few crystals of iodine. Iodine sublimes from solid to gas and the gas turns the spots brown. Circle with a pencil
- Calculate rf value by dividing distanced travelled by spot by distance travelled by solvent
- Use stable of known values to identify compounds present in the mixture
What is a pharmacophore?
The part of the drug that fits into receptor and makes it medicinally active is called the pharmacophore.
Fit of pharmacophore depends on
Size and shape
Bond formation
Orientation e.g. if it has optical or trans/cis isomers
What are enantiomers?
Also called optical isomers
A chiral carbon atom is an atom with 4 diff groups attached also called chiral centre
Optical isomers are mirror images of each other and no way you turn them can be superimposed
If it can be superimposed on the mirror Image, it’s achiral and doesn’t have an optical isomer
Amines?
Suffix amine
NH2 func group
Amine is base as can accept proton to become cation
You can neutralise amine by reacting it with an acid to make an ammonium salt:
RNH2 + HX > RNH3+
Amides?
Suffix amide
Functional group CONH2
Primary amides nitrogen bonded to one carbon secondary amides nitrogen bonded to 2 carbon atoms.
Carbonyl group pulls electrons away from rest of group, so amides behave diff to amines
They can be hydrolysed in acidic and basic conditions:
Heat with dilute acid to get carboxylic acid and ammonium salt.
Or heat with dilute alkali to get carboxylate ion and ammonia gas
Carboxylic acids?
They are weak acids they partially dissociate into carboxylate ions and hydrogen ions
They react with metals in redox reaction to from salt and hydrogen gas
They react with carbonates to form salt, water and carbon dioxide
They react with aqueous alkalis to form salt and water
Esters?
Func group R-C=O-OR
Made by reacting alcohol with a carboxylic acid
To name first part comes from alkyl group that came from alcohol e.g propyl
Second part comes from replacing the oic from acid it came from with oate e.g ethanoic acid > ethanoate
How can esters be hydrolysed to form alcohols?
Acid hydrolysis makes carboxylic acid and alcohol:
Reflux with acid Ester + H2O ⇌carboxylic acid + alcohol
Base hydrolysis
Reflux ester + NaOH > carboxylate salt + alcohol
Acyl chlorides?
Carboxylic acid derivative
Suffix oyl chloride
They easily lose their chlorine
Alcohol: vigorous reaction at room temp producing ester and HCl
Amines: violent reaction at room temp producing secondary amide and HCl
How are polymers made?
From decarboxylation acid and diamine monomers
How are polyesters made?
From decarboxylic acid and diol monomers
Addition polymers vs condensation polymers?
Addition: alkenes, C=C bond breaks and monomers join. Main polymer chain is unreactive.
Condensation: Each monomer must have to functional groups that can react
Condensation reaction join them.
Monomers are amide or ester links which can be hydrolysed in acidic or basic conditions to break the polymer down.
Nylons?
Type of polyamide ( made from diamine and dicarboxylic acid)
Nylon -x,y
x = number of carbons in the diamine
Y = number of carbons in the dicarboyxlic acid
Some nylons made of one monomer:
Nylon-x
X = number of atoms of carbon
Why are some fragments not detected by the mass spectrometer?
When a molecule fragments, it splits into a positively charged ion and uncharged radical.
Mass spectrometer only detect charged particles
Some charged fragments are also unstable, breaking down before they had time to be detected
13C NMR spectra?
Tells you about carbon environments
- Count number of carbon environments. Ignore peak at zero as this is TMS reference. So 3 peaks excluding one at zero = 3 carbon environments
- Look up chemical shifts on data sheet and match up with peaks on the spectrum.
- Try out possible structures
1H NMR Spectra?
Tells you about hydrogen environments
- Each peak represents one hydrogen environment
- Look up chemical shifts on data sheet.
- In 1H NMR, relative area under each peak tell you hlw many H atoms in each environment. E.g. if ratio 2:1, twice as many H atoms in first environment than in the second.
What can the number of splits in a peak on 1H tell you?
You can work out the number of neighbouring hydrogen by how many peak splits into
If a peak splits into two (doublet ) then there’s one hydro on neighbouring carbon
If a peaks split into 3 (triplet) there are two hydrogen on neighbouring carbon.
Etc
