Amines

• What test tube reaction would distinguish between benzene and cyclohexene?


  Bromine water would decolourise in cyclohexene.

  No colour change in benzene.
• Why is nitrogen B more likely to be protonated?

  As the lone pair on B is more readily available due to the alkyl groups pushing electrons towards Nitrogen. The delocalise benzene ring pulls electrons away from nitrogen a making its lone pair less readily available.

  
• How would you distinguish between ammonia and methyl amine?


  Measure pH with a meter. Methyl amine would have a higher pH.
• What catalyst is used to reduce nitrobenzene into phenylamine?


  HCl
• Give the IUPAC name for serine?

  2-amino-3-hydroxypropanoic acid.

  
• What is the reagent and mechanism for reaction 3 + 4?


  Reaction 3= HBr. Electrophilic addition.

  Reaction 4= Excess ammonia. Nucleophilic substitution.

  
• Name functional group J and K?


  J= Amide

  K= Secondary amine

  
• Why is CDCl3 used as a solvent in H1 NMR?


  As solvent must be proton free to not give peaks in spectrum.

  It is also polar, so more effective for polar molecules.
• What is an adv and dis of using a racemate over a single enantiomer in medicine?


  adv= cheaper medicine due to cost as no need to separate.

  dis= 1 enantiomer may cause side effects in mixture.
• Name the compound (CH3CH2)2NH


  Diethylamine
• Give equation to form NO2+?


  HNO3 + H2SO4 > H2NO3+ + HSO4-

  H2NO3+ > NO2+ + H2O
• Why is an amine a stronger base than ammonia?


  Alkyl group increases electron density on nitrogen lone pair making it more readily available.
• What is a cationic surfactants?


  Quaternary ammonium salts used to make cleaning products.

  Non polar tail attracted to oil.

  Positive head attracted to water.

  This allows water and oil to mix, removing grease.
• How do amines act as base?


  They have a lone pair of electrons, allowing them to accept a proton.

  Proton bonds to amine via a dative bond.
• What does the strength of a base depend on?


  Availability of the lone pair of electrons. The higher the electron density, the more readily available electrons are.
• Why are aliphatic amines the strongest?


  Alkyl groups are electron pushing, so push electrons to Nitrogen. Electron density at Nitrogen increases, so lone pair availability is increased.
• Why is benzene the weakest base?


  Benzene is an electron withdrawing group, so pulls electrons away from nitrogen. Electron density at nitrogen decreases, so lone pair availability is reduced.
• Making aliphatic amine by reacting halogenoalkane with EXCESS ammonia?


  -: reaction produces impure products as primary amine still has lone pair to react with any remaining halogenoalkane.

  Nucleophilic substitution.

  
• Making aliphatic amine by reducing nitriles using H2 and nickel catalyst?


  +: Produces primary amines only. Pure product made.

  High temp/pressure.

  eg CH2-C=N + 2H2 > CH2-CH2-NH2
• Making aliphatic amine using LiAlH4 and dilute acid?


  -: More expensive.

  CH2-C=N + 4[H] > CH2-CH2-NH2
• How to make aromatic amines?


  Reduce nitro compounds using HCl and tin to make a salt.

  Salt is reacted with NaOH to produce aromatic amine.

  Reflux reaction.
• What are aromatic amines used for?


  Making dye stuffs and pharmaceuticals.

  Explosives (TNT)
• What type of mechanism is reaction 1?

  Electrophilic substitution.

  
• Whats a reducing agent from nitrobenzene to phenylamine?

  Sn and HCl
• Give a use for a phenylamine?

  Making dyes.

  Making fabric softener.

  Making quaternary ammonium salts.
• [CH3 (CH2 )15N(CH3 )3]+Br– What compound is this?

  Quaternary ammonium salt.
• How would you distinguish between ammonia and methylamine?

  Measure pH with a meter. Ammonia has a lower pH.
• Benzene to cyclohexane?

  H2, Ni
• Why can polyamides be made into fibres for sewing but polyalkenes usually produce fibres that are too weak for this purpose?

  Hydrogen bonding in polyamides has stronger forces of attraction compared to VDW forces in polyalkenes.
• Compare benzenes stability compared to cyclohexatriene?

  Benzene is more stable as its expected enthalpy of hydrogenation is -360, but its actual is 152 due to electron delocalisation.
• Suggest why CDCl3 and not CHCl3 was used as the solvent in H NMR?

  Solvent must be proton free.
• Suggest one advantage and one disadvantage of using a racemate rather than a single enantiomer in medicines?

  Adv- Cheaper medicine due to cost of separation.

  Dis- Side effects from 1 enantiomer in mixture.
• State the difference in the biodegradability of Kevlar compared to that of rubber made of polymerised alkenes?

  Kevlar is biodegradable but polyalkenes aren't.

  Kevlar has polar bonds , so can be hydrolysed by nucleophilic attack.

  Polyalkenes aren't polar.
• Benzene to nitrobenzene?

  Conc HNO3 and conc H2SO4

  Electrophilic substitution
• How could you use IR spectra in the range outside the fingerprint region to distinguish between the secondary amine and the tertiary amine?

  N-H bond is only present in secondary amines.
• Why is butylamine a stronger base than ammonia?

  Lone pair on nitrogen has increased electron density due to alkyl groups pushing electrons to it. This makes the lone pair more readily available.
• why are amines so reactive?

  the lone pair of electrons on the nitrogen due to polar n-h bond
• what shape are amines around the N?

  trigonal pyramidal, 107 degrees
• are amine intermolecular forces stronger than alcohols?

  weaker as N has a lower electronegativity than O, weaker hydrogen bonding
• what do amines smell off?

  fishy smell