organic II Flashcards
(34 cards)
What is the Sn2 mechanism?
Draw example mechanism.
Nucleophillic substitution with two species involved in the rate determining step and 2nd order.
Includes a transition state.
Page. 174
What is the Sn1 mechanism?
Draw example mechansim.
Nucleophillic substitution with one species involved in the rate determining step and first order.
Includes a carbocation with a planar shape.
Equal chance of nucleophile attacking from left or right so 2 products formed: a racemic mixture.
Page. 175
How to form an achohol from an aldehyde or ketone?
Reduction of aldehyde/ ketone using LiAlH4 (lithium aluminium hydride) and dry ether solvent.
How can you identify an aldehyde? (4 ways)
- Acidified potassium dichromate (VI) - orange sol to green sol.
- Fehling’s solution - deep blue sol to red precip
- Benedict’s solution - deep blue sol to red precip
- Tollen’s reagent - colourless sol to silver mirror
How can you identify a ketone?
- React with iodine - yellow precip
Reaction of carbonyl compound with KCN and mechanism.
- Nucleophillic addition
- Produces Hydroxynitrile racemic mixture
page. 180
How to test for carbonyl compound?
- Brady’s reagent (2,4-DNPH) - forms orange precip
How to form a carboxylic acid by hydrolysis?
- Hydrolysis of nitrile - heat under reflux and dilute acid/ aqueous alkali
- equation on page. 184
How can you reduce a carboxylic acid?
- LiAlH4 reducing agent and solvent of dry ether
- Produces a primary alcohol and water
How can you neutralise a carboxylic acid and what is the product?
- mixing with aqueous alkali
- makes sodium X-oate
- equation on page. 185
Halogenation of a carboxylic acid.
- PCl5 (phosphorus (V) chloride)
- Forms an acyl chloride
- equation on page. 185
Esterification of a carboxylic acid.
- Carboxylic acid is mixed with an alcohol and a small amount of acid catalyst (usually conc. sulfuric acid)
- Forms an ester and water
- equation on page. 185
What happens when you react an acyl chloride with water?
- Forms a carboxylic acid and hydrogen chloride gas (misty fumes)
- equation on page. 186
What happens when you react an acyl chloride with an alcohol?
- Forms an ester and hydrogen chloride gas (misty fumes)
- equation on page. 186
What happens when you react an acyl chloride with conc. ammonia?
- Forms an amide and hydrogen chloride gas (misty fumes)
- HCl then reacts with NH3 (as acid and base) to form ammonium chloride
- equation on page. 187
What happens when you react an acyl chloride with an amine?
- Forms an N-substituted amide and hydrogen chloride gas (misty fumes)
Hydrogenation on benzene.
- Mix benzene with hydrogen, heating under pressure and nickel catalyst to form cyclohexane
- equation on page. 196
Combustion of benzene.
- Smoky flame
- equation on page. 196
Bromination of benzene.
Mechanism.
- Bromine and benzene are heated under reflux in the presence of a catalyst: halogen carrier (usually aluminium chloride or bromide) but iron filings in this reaction
- Forms bromobenzene and HBr
- equation on page. 196
Nitration of benzene
Mechanism.
- Warming benzene with conc. nitric acid and sulfuric acid
- Forms nitrobenzene and water
- equation on page. 196
Friedel crafts alkylation of benzene.
Mechanism.
- Halogenoalkane with halogen carrier (AlCl3)
- Forms alkylbenzene and hydrogen halide
- equation on page. 197
Friedel crafts acylation of benzene.
Mechanism.
- Acyl chloride and halogen carrier (AlCl3)
- Forms ketone and hydrogen halide
- equation on page. 197
Bromination of phenol
- Room temp without catalyst with bromine water
- bromine water is decolourised to form a white precipitate
- equation on page. 200
How to form an amine from a halogenoalkane?
- heating halogenoalkane with ammonia (nucleophile) under pressure and in a sealed container or mixed with conc. aqueous ammonia
- forms alkyl amine and hydrogen chloride
- alkyl amine acts as a nucleophile reacting with halogenoalkane to form a secondary amine and HCl
- ammonia used in excess to avoid unwanted side-reactions, some of excess ammonia reacts with HCl to form NH4Cl
- equation on page. 202
