Amines
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How do you prepare amines?
Halogenoalkane is heated with an excess of ammonia dissolved in ethanol This is carried out in a Sealed tube immersed in water: it’s a NUCLEOPHILIC substitution reaction
In preparing amines, what else happens as a result of the amine being basic?
A soluble anime salt is formed as the basic anime accepts H+ from HX (Eg HCl) RCH2NH2 + HX –> RCH2NH3+X-
Do amines dissolve in hydrochloric acid? Explain
Yes amines dissolve in HCl because a soluble salt is formed CH3CH2NH2 + HCl –> CH3CH2NH3+Cl-
In order to make an amine from a amine salt what would you do?
Treat salt with NaOH - AN ALKALI to produce it CH3CH2NH3+Cl- + NaOH –> CH3CH2NH2 + NaCl + H2O
What other compound can follow the path of the salt dissolving in HCl and being treated with NaOH?
Phenylamine
How do you prepare phenylamine ?
1-nitrobenzene is reduced with Tin and HCl 2- mixture is heated and a salt is formed which is soluble in water 3-NaOH (aq) is added to produce phenylamine Steam distillation separates phenylamine and nitrobenzene
How would you separate phenylamine from nitrobenzene ?
Steam distillation
Reagents and conditions to prepare phenylamine
1-Sn and HCl (heat) 2-NaOH(aq)
What is the basic nature of amines
They are all basic because the nitrogen atom has a lone pair of electrons which accept a proton. The nitrogen atom forms a coordinate a dative covalent bond with the proton H+ - it donates an electron pair
Observation of amines with universal indicator
It turns blue purple
Observation of amines with red litmus
It turns blue
What is the basic strength of aliphatic and aromatic amines?
Aliphatic: stronger bases than ammonia NH3 Aromatic: weaker bases than ammonia NH3
Describe the basic strength of phenylamine (an aromatic amine)
The electron density on the LP of the nitrogen is decreased due to the inductive effect of the aromatic ring. The ring is electron withdrawing so the Nitrogen accents H+ less readily. The lone pair is delocalised onto the ring
Describe the basic strength of ethyl amine (aliphatic amine)
Electron density on the LP of nitrogen is increased due to the inductive effect of the ethyl group. The alkyl group is electron donating so the N accepts H+ more readily: it’s a strong base
What bonding occurs between amine molecules?
Hydrogen! It is a strong intermolecular force so the MPs and BPs are higher than expected: lots of energy needed to overcome these
Compare bonding in amines and alcohols..
H bonding in amines is weaker than in alcohols as the Nitrogen is less EN than the O, so alcohols have higher BPS
What do amines contain?
A permanent dipole
General formula of an amine
RNH2
Conditions for reactions of amines with ethanoyl chloride
Dry conditions Fume cupboard as hydrogen chloride produced Ethanoyl chloride
What do reactions of amines wth ethanoyl chloride produce?
N-substituted products Ending always ethanamide is CH3COCl used
What type of reaction is the one between amines and ethanoyl chloride?
NUCLEOPHILIC substitution or ethanoylation
If methylamine reacts with CH3COCl what is the products?
N-methylethanamide + HCl
If phenylamine is reacted with CH3COCl what is the products?
N-phenylethanamide + HCl
General equation for the reaction of amines with ethanoyl chloride
CH3COCl+ H2NR —> CH3CONHR + HCl