organic stuff I forget - last 8 topics

uses of esters

• Food flavourings - mixture of esters

• Many perfumes contain mixtures of esters in solvent that quickly evaporates

• Often used as solvents

• Esters can be used as plasticisers - added to polymers to make them more flexible

what are vegetable oils and fats esters of

propane-1,2,3-triol

saponification in alkaline conditions

• aqueous/warm

• Bases also catalyse hydrolysis of esters - salt of the acid is produced rather than the acid itself

• Removes the acid from reaction mixture so equilibrium not established and reaction goes to completion

if vegetable oils/fats hydrolysed using bases what is use

soap, Hydrocarbon will mix with grease while COO- mixes with water

what is biodiesel

mixture of methyl esters made of long-chain carboxylic acids

Lipid is broken down into fatty acids and glycerol by reaction with potassium hydroxide (catalyst) and methanol

why ethanoic anhydride better than ethanoyl chloride

• Less corrosive, less vulnerable to hydrolysis, does not form HCl

• No HCl produced - toxic gas

• Less exothermic reaction/less vigorous reaction

• Easier to control

• Cheaper and more easily recycled

benzene BS

why no addition

• Ring is an area of high electron density because of delocalised bonding and attacked by electrophiles

• Aromatic ring is very stable, needs energy to be put in to break the ring before system can be destroyed

  • Called delocalisation energy - means that the ring almost always remains intact in the reactions of arenes

• Aromatic systems mostly react by electrophilic substitution reactions due to these reasons

why nitration and acylation useful

important step in synthesis, including manufacture of explosives and forming amines (for azo dyes)

acylation - important in synthesis

base strength amines

Primary aromatic < ammonia < primary aliphatic for base strength

Primary aromatic - lone pair on N is less available as it is delocalised into ring

Primary aliphatic - positive inductive effect makes lone pair on N more available

why is reduction w nitriles better than nuc substitution

No further reactions/single product so higher atom economy

nucleophilic substitutions with amines

If large excess of ammonia used - main product is primary amine

If large excess of haloalkane used - main product is quaternary ammonium salt

what are quaternary ammonium salts used for

cationic surfactants, hair conditioner

ionic head is hydrophilic whereas hydrocarbon tail is hydrophobic

uses of Kevlar, Terylene and nylon 6,6

Kevlar - bulletproof vests, PPE

Terylene - fine fibres/artificial fabrics

nylon 6,6 - clothing, substitute for silk, makes ropes, Velcro

why condensation polymers are biodegradable

polar bonds in their chains, open to attack by nucleophiles

how to hydrolyse protein

conc HCl, hot

developing agents used for TLC of AA

ninhydrin or UV light

why do hydrogen bonds form

Nitrogen and oxygen are very electronegative

Therefore, C=O and N—H are polar

Which results in the formation of a hydrogen bond between O and H

Lone pair on O strongly attracted to delta positive H

why are disulfide stronger than hydrogen bonds

disulfide bridges are covalent bonds

enzyme stuff

Enzyme has active site

Enantiomer has complementary shape

enzyme is stereospecific, drugs can act as enzyme inhibitors

computers used to design these drugs

random stuff about DNA

Amino groups in urea are able to substitute for the H-bonds in the double helix

cisplatin prevents DNA replication

ligand replacement reaction with N on guanine - it is the Cl ligands that are replaced

cisplatin affects normal cells as well

what do I need to know about TMS (non-toxic), or solvents

what is chromatography used for

separate and identify components in a mixture

TLC

• Use plastic sheet/metal/glass coated with thin layer of silica gel (silicon dioxide) or aluminium oxide/alumina

• This acts as stationary phase

column chromatography

• Uses powder such as silica, aluminium oxide or resin as stationary phase

• This is packed into narrow tube and solvent/eluent is added at the top

• The eluent runs down column, components of mixture move at different rates and can be collected separately in the flasks at the bottom

• More than one eluent may be used - fairly large amounts can be separated and collected

gas chromatography

• Stationary phase is powder/powder covered in oil, packed into or coated on inside of long capillary tube

• Placed in oven

• Mobile phase is unreactive gas like nitrogen or helium

• Components leave the column at different times = different retention time

• Under pressure at high temperature

how does GCMS work

• Mass spectrometer is used as detector for gas chromatography system

• As each component of mixture comes out of the column, time it has taken to pass through is noted, each component is fed automatically into mass spectrometer

• Enable compound to be identified either by its fragmentation pattern or by measuring its accurate mass

key phrase

different relative affinity for mobile and stationary phase

balance between solubility in the mobile phase and retention by the stationary phase

lid for chromatography to…

Prevent solvent evaporating from the tank/jar

Maintain constant atmosphere that is saturated with solvent vapour

Prevent solvent evaporating off the surface of the plate as it rises up