organic synthesis [O2] PAPER 2 Flashcards
Suggest why chemists usually aim to design production methods with fewer steps.
• less energy used
• better yield
Suggest why chemists usually aim to design production methods with a higher atom economy.
• less waste
• less pollution
[X=halogen]
reaction between a haloalkane and NaOH to form an alcohol and NaX
- conditions?
- mechanism?
- what is the role of NaOH?
- warm, aqueous
- nucleophilic substitution
- nucleophile
[X=halogen]
reaction between a haloalkane and KCN to form a cyanide and KX
- conditions?
- mechanism?
- what is the role of CN?
- warm, ethanolic, aqueous
- nucleophilic substitution
- nucleophile
[X=halogen]
reaction between a haloalkane and ammonia to form an amine
- conditions?
- mechanism?
- what is the role of NH3?
- excess concentrated ethanolic NH3
- nucleophilic substitution
- nucleophile (and base for the second step?)
[X=halogen]
reaction between a haloalkane and KOH to form an alkene, water and KX
- conditions?
- mechanism?
- role of OH ions?
- hot, ethanolic
- elimination
- base
what are the three steps of free-radical substitution?
- initiation
(molecule -> radical + radical) - propagation
(molecule + radical -> radical + molecule) - termination
(radical + radical -> molecule)
what conditions are required for free-radical substitution and why?
• UV light
• break (C-X, C-H) bonds
[X=halogen]
name and outline the mechanism to form a halogenoalkane from an alkene and Br2 / HBr
• electrophilic addition
• Br2 / HBr = electrophile
(mechanism is the same for Br2 - just Br instead of H)
name and outline the mechanism for the reaction between an alkene and sulfuric acid, and state conditions required
• electrophilic addition
• conditions: concentrated H2SO4, cold (typically room temp.)
outline the reaction and conditions to form an aldehyde from the oxidation of an alcohol, and the further oxidation of the aldehyde to form a carboxylic acid
• 1° alcohol + [O] -> aldehyde + water
• aldehyde + [O] -> carboxylic acid + water
• warmed with acidified potassium dichromate (VI)
• distilled [aldehyde is distilled off - if this isn’t done, it would oxidise to form the carboxylic acid]
e.g. ethanol:
outline the reaction, conditions and reagent used to form a carboxylic acid from the oxidation of an alcohol
• 1° alcohol + 2[O] -> carboxylic acid + water
• conditions: under reflux
• reagent: acidified potassium dichromate (VI)
e.g.
outline the reaction and conditions for the formation of a ketone from an alcohol
• 2° alcohol + [O] -> ketone + water
• acidified potassium dichromate (VI)
• reflux
e.g.
Reagent, conditions and mechanism for the dehydration of an alcohol to form an alkene?
• conc. sulfuric/phosphoric acid
• hot
• elimination
a mixture of alkenes can be formed depending on the alcohol (different carbocations)
name the reaction, conditions and outline the mechanism to form an alcohol from an alkene
• electrophilic addition (hydration too)
• alkene + steam -> alcohol
• conc. H2SO4 catalyst
• this is how ethanol from ethene can be obtained
name and outline the mechanism, state the reagent, and the conditions for the reduction of aldehydes to primary alcohols / ketones to secondary alcohols.
• nucleophilic addition
• NaBH4
• aqueous
name and outline the mechanism, state the reagents, and the conditions for the reaction of carbonyl compounds to produce a hydroxynitrile.
• nucleophilic addition
• KCN and dilute acid
• aqueous
esterification/ester hydrolysis reaction and conditions?
• alcohol + carboxylic acid ⇌ ester + water
• above the other way round = ester hydrolysis (in acidic conditions)
• concentrated strong acid catalyst, e.g. H2SO4
e.g.
saponification reaction?
• ester + alkali → salt of carboxylic acid + alcohol
• this is ester hydrolysis in alkaline conditions
saponification of a lipid?
lipid + 3KOH → 3 salts of fatty acids + glycerol
name and outline the mechanism for the acylation of R—OH using R—COCl.
nucleophilic addition-elimination
name and outline the mechanism for the acylation of R—NH2 using R—COCl.
nucleophilic addition-elimination
name and outline the mechanism, and state the reagents and conditions, for the nitrification of benzene.
• electrophilic substitution
• conc. HNO3
• conc. H2SO4
• 50°C
name and outline the mechanism, and state the reagents and conditions, for the Friedel-Crafts acylation of benzene.
• electrophilic substitution
• acyl chloride/acid anhydride
• AlCl3 catalyst
• anyhydrous
generation of electrophile for the nitration of benzene?
