Amines

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Amines Intro...

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As quaternary ammonium ions are + charged they will hang aroung - ions.  The complexes formed are called quaternary ammonium salts.      Small amines smell like ammonia, "fishy" twist. Larger ones smell very "fishy"

NAMING: end -amine.     begining depends on what organic groups are attached. If all organic groups are the same then you need to add... di- for secondary amines, Tri- for tertiary amines and tetra- for quaternary ammonium ions. (e.g. Diethylamine or Tetramethylamine ion)

If it has more than one type of organic group, list different groups in alphibetical order. (e.g. Methylpropylamine)

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Cationic Surfactants

Surfactants are partially soluble and partially in-soluble in water.                                                        Some quaternary ammonium compounds can be used as cationic surfactants. These compounds are quaternary ammonium salts with at least one long hydrocarbon chain ---> insoluble in water. + charged head is soluble.

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Used in things such as fabric conditioners and hair products. Forms coating over - charged surface. Preventing the build up of static electricity.

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Forming Dative Covalent Bonds (Base Properties)

Amines act as Bronsted-Lowry basses because they accept protons. There is a lone pair of electons on the nitrogen atom that forms a dative covalent (coordinate) bond with a H+ ion.

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Strength of base depends on avaliabilty of nitrogens lone pair. A lone pair will be more avaliable if electron density is higher. More avaliable a lone pair is, more likely the amine is to accept a proton, so the stronger the base will be.                                                                                          AROMATIC AMINES: WEAK. Because the benzene ring draws electrons towards itself and the nitrogens lone pair gets partially delocalised onto ring. So electron density on nitrogen decreases, lone pair less avaliable.                                                                                                             PRIMARY ALIPHATIC AMINES: STRONG. Because alkyl groups push electrons onto ring, electron density on nitrogen atom increases. making lone pair more avaliable.                                           AMMONIA: LIES INBETWEEN. because ammonia doesnt have aromatic group to pull lone pair of electrons away, or an alkyl group to push electrons forward

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Base Properties Diagram

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Amides

Derivatives of carboxylic acids. Contain functional group -CONH2. Carbonyl group pulls electrons away from NH2, so amides behave differently to amines. General Structure:

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Naming.... suffix -amide and prefix comes from alkyl group (R) (e.g.) Ethanamide)

Also get N-Substituted amides.... when one of the hydrogens on the nitrogen has been substituted for an alkyl group.    Naming...  Starts N-something (e.g N-Ethyl or N-propyl)

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(e.g.) N-Methylethanamide)

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Formation of amines from haloalkanes

Can be made by heating a haloalkane with excess ammonia. Get a mixture of primary, secondary and tertiary amines and quaternary ammonium salts as more than one hydrogen is likely to be substituted. E.G. :

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Can seperate the products using fractional distillation if trying to make one particular amine.

Formation of amines from haloalkanes is nucleophilic substitution. General mechanism:

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Formation of amines from haloalkanes cont..

The amine product still has a lone pair of ellectrons on the nitrogen, so it is still a nucleophile. Meaning further substitutions can take place.   Keep happening until a quaternary ammonium salt is produced, which cant react any further as it has no lone pair of electrons.

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Reaction for further substitutions is the same - use an amine instead of ammonia. E.G:

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Formation of amines from nitriles

Reduce a nitrile to an amine using a strong reducing agent such as lithium aluminium hydride (LiAlH4) followed by some dilute acid.

E.g. Formation of ethylamine from ethanenitrile:

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Another way is to reflux nitrile with sodium metal and ethanol. good in lab but too expensive for industrial use. instead they use a metal catalyst at a high temperature and pressure --> catalytic hydrogenation. 

 

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Formation of aromatic amines

Produced by reducing a nitro compound such as nitrobenzene.

1. heat mixture of nitro compound, tin metal and conc. hydrochloric acid under reflux---> salt

2.Turn salt into aromatic amine, add alkali (e.g. NaOH solution)

E.G: Phenyl Amine made by reducing nitrobenzene

Mix nitrobenzene, tin and conc. HCl and heat under reflux ---> salt C6H5NH3+Cl-

Add NaOH to salt releases phenylamine

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