AQA Chem 4 Reactions
Aldehyde nucleophilic addition reaction:
Nu = nucleophile (e.g. CN).
RCHO +HNu --> RC(Nu)(OH)H
Ketone nucleophilic addition reaction:
Nu = nucleophile (e.g. CN-)
R'CRO + HNu --> R'C(Nu)(OH)R
Reducing an aldehyde using NaBH4 (represented as [H]):
RCHO + 2[H] --> RCH2(OH)
Reducing a ketone using NaBH4 (represented as [H]):
R'CRO + 2[H] --> R'CR(OH)
Formation of an ester (methyl ethanoate) using methanol and ethanoic acid:
CH3COOH + CH3OH <--> CH3COOCH3 + H2O
A strong acid catalyst (e.g. conc. H2SO4) is required. It is a reversible reaction. The reverse reaction is called acid hydrolysis.
Base hydrolysis of esters using methyl ethanoate:
CH3COOCH3 --> CH3COO-Na+
A strong base catalyst (e.g. NaOH in this example) is required. Sodium ethanoate is the product of this reaction. (Note: the bond between O and Na is ionic, so do not draw a covalent bond between them. Instead, show the charges as above).
Hydrolysis of triglyceride using NaOH:
Boil the triglyceride with NaOH.
CH2O(COR)CHO(COR)CH2O(COR) + 3NaOH --> CH2(OH)CH(OH)CH2(OH) + 3NaOCOR
Glycerol (propane-1,2,3,-triol) and sodium salts are formed. The salts are used as soaps. Glycerol is used in pharmaceutical and cosmetic preparations, medicines, toothpaste, food colourings and as a plasticiser.
Formation of biodiesel from the reaction of a triglyceride ester and methanol:
CH2O(CO(CH2)14CH3)CHO(CO(CH2)14CH3)CH2O(CO(CH2)14CH3) + 3CH3OH --> CH2(OH)CH(OH)CH2(OH) + 3 CH3OCO(CH2)14CH3
Electrophilic addition reaction of benzene:
El = electrophile (e.g.NO2+)
C6H6 + El+ --> C6H5El + H+
Formation of the nitronium ion to catalyse the nitration of benzene:
Concentrated sulfuric acid (catalyst) and concentrated nitric acid is required.
H2SO4 + HNO3 --> H2NO3+ + HSO4-
H2NO3+ then loses a water molecule and forms NO2+ which is the nitronium ion:
H2NO3+ --> NO2+ + H2O