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9 Cards in this Set
- Front
- Back
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Primary amine |
-has only one carbon atom bonded to the nitrogen atom and, therefore, has an -NH2 group. e.g. Methylamine CH3NH2 |
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Secondary amine |
-has two carbon atoms directly joined to the nitrogen atom. All secondary amines have an -NH group. |
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Tertiary amine |
-has a three carbon atom and no hydrogen atoms attached directly to the nitrogen atom. e.g. Trimethylamine. |
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Preparation: Reaction of ammonia with halogenoalkane |
-if halogenoalkane is mixed with excess concentrated ammonia in aqueous ethanolic solution and left for several minutes, a primary amine is obtained: C2H5CL+2NH3---- C2H5NH2+NH4CL -excess of ammonia will yield the secondary amine. -another condition for this reaction, often quoted in a textbooks and accepted by examiners, is heating the mixture in a sealed tube. |
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Preparation: Reduction of nitrile or amide |
-a nitrile (e.g. ethanitrile) or an amide (e.g. ethanamide) can be reduced by warming with a solution of lithium tetrahydridoaluminate (III) in dry ether (ethoxyethane), followed by hydrolysis of adduct with dilute acid: -Ch3CN+4[H]-----------CH3CH2NH2 ethanenitrile ethylamine -CH3CONH2+[H]---------CH3CH2NH2+H2O ethanamide ethylamine |
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Preparation: Hofmann degradation of an amide |
-if liquid bromine and aqueous sodium hydroxide are added to an amide, an amine with one fewer carbon atoms than the amide is produced, e.g: CH3CH2CONH2+Br2------ch3ch2nh2+NaCO3+2NaBr+2H2O The yield of this reaction high. |
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Chemical reactions: As base |
-the base reaction of amines are similar to those of ammonia. -ammonia and amine molecule have a lone pair of electrons on the nitrogen atom that can be used to form a dative covalent bond with an H+ ion. |
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Chemical reaction: Reaction with water |
Amines react reversibly with water, e.g: -C2H5NH2+H2O--------C2H5NH3+OH- As OH- ions are produced, the solution is alkaline, with a pH of about 11. This reaction is similar to: -NH3+H2O------------NH4+ +OH- |
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Chemical reaction:
Reaction with water continue |
-NH3+H2O------------NH4+ +OH- The C2H5 group pushes electrons slightly towards the nitrogen atom making it more delta- than it is in ammonia. Therefore, ethylamine is a stronger base than ammonia: -Kb of ethylamine=5.6*10-4 moldm-3 -Kb of ammonia=1.8*10-4 moldm-3 |
