Exam Qs Amines
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In the manufacture of ibuprofen both isomers F and G are formed. An enzyme is then used to bind to isomer G and catalyse its hydrolysis. After the products of hydrolysis of G are removed, a pure sample of isomer F is collected. Explain how a structural feature of this enzyme enables it to catalyse the hydrolysis of isomer G but not the hydrolysis of isomer F.
G enantiomer has correct sterochemistry So enzyme has complimentary shape
1,6-Diaminohexane can also be formed in a two-stage synthesis starting from 1,4-dibromobutane. Suggest the reagent and a condition for each stage in this alternative synthesis.
Stage 1 - kcn in aqueous ethanol Stage 2 - h2 and ni
Explain why 3 aminopentane is a stronger base than ammonia
Isomer F is the active compound in the medicine ibuprofen. In the manufacture of ibuprofen both isomers F and G are formed. An enzyme is then used to bind to isomer G and catalyse its hydrolysis. After the products of hydrolysis of G are removed, a pure sample of isomer F is collected. Explain how a structural feature of this enzyme enables it to catalyse the hydrolysis of isomer G but not the hydrolysis of isomer F.
The g enantiomer has the correct stereochemistry So enzyme has complimentary shape
1,6-Diaminohexane can also be formed in a two-stage synthesis starting from 1,4-dibromobutane. Suggest the reagent and a condition for each stage in this alternative synthesis.
Stage 1 - kcn in aqueous ethanol Stage 2 - h2 and ni
Explain why 3-aminopentane is a stronger base than ammonia.
n 3-aminopentane Lone pair on N more available or Lone pair on N accepts H+ better because of alkyl electron pushing /inductive effect
Justify the statement that there are no chiral centres in 3-aminopentane.
No carbon (atom is) attached to 4 different groups
Amine F can be prepared in a three-step synthesis starting from methylbenzene. Suggest the structures of the two intermediate compounds. For each step, give reagents and conditions only. Equations and mechanisms are not required. Amine f is a benzene ring attatched to CH2CH2NH2
Intermediate compounds Product of step 1 C6H5CH1Cl Product of step 2 C6H5CH2CN Step 1 Cl2 & UV free radical substitution Step 2 KCN alcoholic & aq (both reqd) nitrile Step 3 H2 / Ni or Pt or Pd
Explain why butylamine is a stronger base than ammonia.
Lone pair (on N) (in correct context) R group increases electron density / donates electrons /pushes electrons / has positive inductive effect
Outline a mechanism for the formation of ethylamine from bromoethane. State why the ethylamine formed is contaminated with other amines. Suggest how the reaction conditions could be modified to minimise this contamination.
Nucleophilic substitution nh3 in excess heat under reflux Further reaction / substitution / formation of 2° / 3° amines etc (1) use an excess of NH3
Suggest one reason why phenylamine cannot be prepared from bromobenzene in a similar way. Outline a synthesis of phenylamine from benzene. In your answer you should give reagents and conditions for each step, but equations and mechanisms are not required.
Benzene repels nucleophiles such as nh3