OCR Chemistry A - Organic reactions & mechanisms

Alkane to Haloalkane

Halogen and UV light

Haloalkane to Alcohol

nucleophilic sub NaOH, h2so4 catalyst, reflux

Alkene to Alkane

H2, Ni catalyst

Alcohol to Haloalkane

Sodium halide/H2SO4

Alkene to Alcohol

H2O (steam)/H3PO4

Alcohol to Alkene

H3PO4, heat

secondary alcohol to ketone

K2Cr2O7, H2SO4, reflux

Primary alcohol to aldehyde

K2Cr2O7/H2SO4, distil

primary alcohol to carboxylic acid

K2Cr2O7, H2SO4, reflux

Haloalkane to Nitrile

NaCN or KCN, ethanol, reflux

Haloalkane to Amine

NH3/ethanol
EXCESS ETHANOLIC AMMONIA

ketone to secondary alcohol

NaBH4

aldehyde to primary alcohol

NaBH4

Alcohol to Ester

Carboxylic acid/conc. H2SO4

OR

Acid anhydride

Carboxylic acid to ester

Alcohol/conc H2SO4/heat

Aldehyde/Ketone to Hydroxynitrile

NaCN(aq)/H+(aq)

Hydroxynitrile to Amine

H2/Ni

Hydroxynitrile/Nitrile to Carboxylic acid

H2O, HCl, Heat

ester to carboxylic acid

dilute acid, heat

Ester to Carboxylate

OH-, heat

Acyl chloride to ester

alcohol

Acyl chloride to carboxylic acid

H2O

Carboxylic acid to acyl chloride

SOCl2

Acyl chloride to primary amide

NH3

Acyl chloride to secondary amide

primary amine

nucleophilic addition

Carbonyl compounds with NaBH4
Ketones/aldehydes to hydroxynitriles

Nucleophilic substitution

Haloalkane to alcohol

Electrophilic addition

Alkene to haloalkane

Electrophilic substitution

Benzene

Kekule's model

Evidence to disprove Kekule's model

Does not react readily with bromine (does not undergo electrophilic addition)

Hydrogenation enthalpy less exothermic than expected

Length of C-C bonds

Delocalised model of benzene

Each carbon uses 3 out of 4 electrons to bond to 2 other carbons
Each electron has electron in p-orbital
P-orbitals overlap sideways above and below the plane to form ring of electron density
Creates system of pi-bonds

Phenol to Nitrophenol

dilute HNO3

What can phenol not react with?

Na2CO3

Why is phenol more reactive than benzene?

Lone pair of electrons in p-orbital of oxygen atom delocalise into the benzene ring
Electron density increased
Less stable
More susceptible to electrophilic attack

Bromination of phenol

Forms white ppt
Bromine decolourises
Room temp.

Nitration of phenol

Mixture of 2-nitrophenol and 4-nitrophenol
Room temp.

Test for carbonyl group

Add 2,4-DNPH
If present, orange ppt forms
Recrystallise
Measure melting point
Compare to known values

Test for aldehydes

Tollens reagent: silver mirror if aldehyde present

Silver ions act as oxidising agent
Aldehyde oxidised to carboxylic acid

Why are carboxylic acids soluble in water?

Polar C=O and O-H bonds allowing them to hydrogen bond.

Carboxylic acids and metals

Hydrogen gas formed (effervescence)
Metal disappears

Carboxylic acid and metal oxide

salt, water

Carboxylic acid and alkali

salt, water

Carboxylic acid and carbonate

Salt, water and carbon dioxide

2 carboxylic acids can condense into a(n) ____________

Acid anydride

Why should preparation of acyl chloride be carried out in a fume cupboard?

Toxic gases produced (HCl, SO2)

Acyl chloride and water

Violent reaction
HCl and carboxylic acid formed

acid anhydride + alcohol

ester + carboxylic acid

Ammonia + acyl chloride

Primary amine + NH4Cl

Primary amine + acyl chloride

Secondary amide + CH3NH3+Cl-

Hydrolysis of Nitriles

nitrile + hcl + 2h20 ---> carboxylic acid + nh4cl

Distillation

A process that separates the substances in a solution based on their boiling points

Reflux

What do anti-bumping granules do?

Prevent large bubbles - even heating

How to purify an organic liquid

Use separating funnel
Add Na2CO3 - this will produce CO2
Invert funnel and open tap to release CO2 - invert until no more gas released
Add more water, the aqueous layer will grow
Separate the layers
Add a drying agent until it stops clumping and a clear solution is formed
Redistil to remove organic impurities
Large range = impure

How to purify an organic solid

Dissolve solid in minimum amount of hot solvent
Filter hot under reduced pressure to remove insoluble impurities (anti-bumping granules)
Leave to cool
Crystals reform
Wash crystals to remove soluble impurities
Dry crystals
Check purity using melting point or TLC

What does a yield over 100% mean?

Not dried properly

What is TMS used for?

Standard reference chemical against which shifts are measured
Gives shift of 0

Stereoisomers

molecules that have the same structural formulas and bonding patterns but different arrangements of atoms in space

Structural isomers

Molecules with the same molecular formula but with different structural arrangements of atoms.

What is a sigma bond?

Orbitals completely overlap

What is a pi bond?

Partials sideways overlap of adjacent p orbitals above and below the plane of the bonding carbon atoms.

Cis/trans isomerism

A special type of E/Z isomerism in which there is a non-hydrogen group and a hydrogen atom on each C of a C=C double bond: the cis isomer (Z isomer) has the H atoms on each carbon on the same side; the trans isomer (E isomer) has the H atoms on each carbon on different sides of the bond.

What is the most stable carbocation?

tertiary carbocation

Recycling polymers

Conserve finite fossil fuels
Decrease waste going to landfill
Polymers must be sorted by type

PVC recycling

Disposal and recycling of PVC hazardous due to high chlorine content
Dumping PVC in landfill not sustainable

Grind PVC and use to manufacture new products

waste polymers as fuel

Some have high stored energy value
Can be incinerated to produce steam to power turbine producing electricity

Feedstock recycling

Chemical and thermal processes that can reclaim monomers, gases or oil from waste polymers

Bioplastics

produced from plant starch, cellulose, plant oils and proteins

Biodegradable polymers

polymers that can be broken down by microorganisms into water, carbon dioxide and biological compounds

Photodegradable polymers

Contain bonds that are weakened by absorbing light to start the degradation

How do CFCs destroy ozone?

Have long residence time in trophosphere
UV breaks down CF2Cl2 into CF2Cl and Cl

Chlorine radicals and ozone depletion

Cl + O3 -> ClO + O2

ClO + O -> Cl + O2

Overall

O3 + O -> 2O2

Nitrogen oxide radicals and ozone depletion