Synthesis Flashcards
Alkene to alkane
- hydrogenation
- 150 degrees
- nickel catalyst
Alkene to dihaloalkane
- Br2/Cl2 etc used
- draw the reaction mechanism
Alkene to alcohol
- hydration
- steam
- high temp and pressure (300 degrees 65 atm)
- hot phosphoric acid catalyst
Alkene to haloalkane
- HBr/HCl used
- draw mechanism
Alkene to polymer
- addition polymerisation
- monomers have the pi bond broken and the electrons from each pi bond make a sigma bond with another monomer
Alcohol to aldehyde
- Oxidise a primary alcohol
- acidified potassium dichromate
- distillation
Alcohol to carboxylic acid
- oxidise a primary alcohol
- acidified potassium dichromate
- reflux
Alcohol to ketone
- oxidise a secondary alcohol
- acidified potassium dichromate
- heat
Alcohol to alkene
- dehydration
- elimination reaction
- heated with strong acid e.g conc H2SO4
- 170 degrees
Alcohol to haloalkane
- halide substitution
- ROH + HX –> RX + H2O
- acid catalyst such as H2SO4
- mixture is warmed
Haloalkane to alcohol
- nucleophilic substitution
- hydrolysis
- water often used, or NaOH
- draw reaction mechanism
Alkanes to haloalkanes
- radical substitution Initiation: - CL2 --> 2Cl' Propagation: - CH4 + Cl' --> 'CH3 + HCl - 'CH3 + Cl2 --> CH3Cl + Cl' Termination: - 2Cl' --> Cl2 - 2'CH3 --> C2H6 - 'CH3 + Cl' --> CH3Cl
Benzene to nitrobenzene
- nitration
- substitution reaction
- reagent is concentrated nitric acid
- sulfuric acid catalyst
- C6H6 + HNO3 –> C6H5NO2 + H2O
- reflux
- draw mechanism
benzene to halobenzene
- halogenation
- halogen carrier is required as the benzene ring is too stable
- iron halides or aluminium halides are used to generate a positive halogen ion
- For chlorination, AlCl3 or FeCl3
- For bromination, AlBr3 or FeBr3
- Br2 + FeBr3 –> Br+ + FeBr4- (bromide ion acts as electrophile)
- draw reaction mechanism
benzene to alkylbenzene
- friedel-crafts
- electrophilic substitution
- haloalkane mixed with halogen carrier which acts as a catalyst and is regenerated at the end
- mixture of products made that can be separated using fractional distillation or chromatography.
- draw mechanism
Benzene to ketone
- friedel-crafts
- acylation
- Acyl chloride used as halogen carrier
- 60 degrees under reflux
- AlCl3 catalyst
phenol to bromophenol
- triple substitution reaction
- reaction with bromine water
- C6H5OH + 3Br3 –> C6H2Br3OH + 3 HBr
- product is a white precipitate of 2,4,6-tribromophenol
Phenol to nitrophenol
- single substitution reaction with dilute nitric acid at room temperature
- mixture of 2-nitrophenol and 4-nitrophenol (2- and 4- directing effect)
- NO catalyst needed
- If conc nitric acid is used, a triple substitution reaction occurs forming 2,4,6-trinitrophenol
- C6H5OH + HNO3 –> C6H4(NO2)OH + H2O
Carbonyl to alcohol
- reduction
- NaBH4 used as reducing agent, source of hydride ion, H-
- CH3COC3H7 + 2[H] –> CH3CH(OH)C3H7
- draw mechanism
esterification
- carboxylic acid and alcohol
- gently heated
- sulfuric acid catalyst
- reversible reaction with slow rate of reaction
- ester is separated using distillation
- To prepare large esters, reflux used and then separated using fractional distillation
Acid anhydride with alcohol
- produces an ester and a carboxylic acid
- irreversible so produces a higher yield than using a carboxylic acid
- rate is slow but can be increased by warming mixture
- ethanoic anhydride+ methanol –> methyl ethanoate + ethanoic acid
Hydrolysis of esters in acidic conditions
- when refluxed with catalyst of hot aqueous acids such as dilute H2SO4 or dilute HCl, ester decomposes reversibly into an alcohol and a carboxylic acid.
- propyl ethanoate + water <=> ethanoic acid + propan-1-ol
Hydrolysis of esters in alkaline conditions
- When refluxed with hot aqueous alkali such as KOH or NaOH, decomposes into alcohol and a carboxylate salt
- irreversible reaction
- this is saponification (to make soaps)
- ethyl propanoate + NaOH –> sodium propanoate + ethanol
Acyl chloride to ester
- reacted with an alcohol
- not reversible so higher yield than using a carboxylic acid
- CH3COCl + CH3CH2OH –> CH3COOCH2CH3 + HCl
Phenol to ester
- React with an acyl chloride
- can’t use a carboxylic acid
- however reaction is violent and produces corrosive fume of HCl
Acyl chloride to carboxylic acid
- small acyl chloride added to water
- quickly hydrolyses
- very exothermic and fumes of HCl are given off
- CH3COCl + H2O –> CH3COOH + HCl
Acyl chloride to primary amide
- reacts with ammonia
- CH3COCl + 2NH3 –> CH3CONH2 + NH4Cl
- ethanoyl chloride + ammonia –> ethanamide + ammonium chloride
Acyl chloride to secondary amide
- Acyl chloride reacts with a primary amide to produce a secondary amide
- nitrogen atom will have two organic groups attached so it is N-substituted
- CH3COCl + CH3CH2NH2 –> CH3CONHCH2CH3 + HCl
- ethanoyl chloride + ethanamide –> N-ethylethanamide + HCl
Preparation of an acyl chloride
-OH group on a carboxylic acid must be substitued for a chlorine atom
CH3COOH + SOCl2 –> CH3COCl + SO2 HCl
Acyl chloride is separated using distillation
Reaction of amine with dilute inorganic acid (HCL and HNO3)
An alkylammonium salt is made
CH3CH2NH2 + HCl –> CH3CH2NH3+Cl-
If nitric acid is used:
CH3CH2NH2 + HNO3 –> CH3CH2NH3+NO3-
Preparation of a primary aliphatic amine
A haloalkane, ammonia and ethanol are heated together. Reflux can’t be used because ammonia is so volatile and would escape out of the condenser.
Stage 1: CH3CH2Cl + NH3 –> CH3CH2NH3Cl
Stage 2: Additional ammonia reacts, CH3CH2NH3Cl + NH3 <=> CH3CH2NH2 + NH4Cl
How would you increase the yield of a primary aliphatic amine?
The reaction is reversible so excess ammonia will drive the reaction to the right and increase the yield of the desired primary amine product
Preparation of a secondary aliphatic amine
Haloalkane and primary amine
Additional substitution of the hydrogen atoms on the nitrogen atom can occur
CH3CH2Cl + CH3CH2NH2 <=> (CH3CH2)2NH + HCl
Preparation of a tertiary aliphatic amine
Further substitution
CH3CH2Cl + (CH3CH2)2NH <=> (CH3CH2)3N + HCl
Haloalkane + tertiary amine
Quaternary ammonium salt is produced
Each hydrogen on the ammonium ion has been replaced by an alkyl chain
CH3CH2Cl + (CH3CH2)3N <=> (CH3CH2)4N+Cl-
Preparation of an aromatic amine
Nitrobenzene reduced to phenylamine
Reducing agent is a mixture of tin and hydrochloric acid
Reflux at 100 degrees
After a while strong alkali such as NaOH is added to undergo a neutralisation reaction and to remove excess HCl and produce the amine.
C6H5NO2 + 6[H] –> C6H5NH2 + 2H2O
How is the aromatic amine separated?
multi stage process including steam distillation, solvent extraction and further distillation
Formation of a polyester
Condensation polymerisation
reaction of a dicarboxylic acid and a diol
ester link forms between molecules
polyester repeat unit - [-O-R-O-CO-R’-CO-]n
Formation of a polyamide
Condensation polymerisation
Reaction of a dicarboxylic acid and a diamine
Amide link forms between molecules
repeat unit - [-NH-R-NH-CO-R’-CO-]n
Haloalkane to nitrile
Nucleophilic substitution Haloalkane mixed with potassium cyanide Heated under reflux Ethanol solvent CH3CH2Br + KCN --> CH3CH2CN + KBr
Cyanide to hydroxynitrile
Carbonyl
Hydrogen cyanide can be used to generate cyanide nucleophile
Nucleophilic addition
Cyanide ion will be attracted to carbon of C=O bond and will form a covalent bond. pi bond opens and the oxygen accepts the extra pair of electrons. This means the negative oxygen can accept a proton and become a hydroxyl group. Racemic mixture made when an aldehyde or an asymmetric keytone is used.
Draw mechanism
Nitrile to amine
Reduction
Hydrogen can react directly with a nitrile to form a primary aliphatic amine
Two hydrogen atoms are added to the nitrogen atom of the nitrile group
Transition metal catalyst such as nickel
Heated to 150 degrees at raised pressure
RCN + 2H2 –> RCH2NH2
Reduction of nitrile using a reducing agent
Reducing agent of LiAlH4
RCN + 4[H] –> RCH2NH2
Nitrile to carboxylic acid
Acid hydrolysis
Reflux
Dilute HCl
CH3CN + 2H2O + HCl –> CH3COOH + NH4Cl
