Amides

=__**Amides**__= __**What are amides?**__

So . . . amides contain the -CONH2 group
The most commonly discussed amide is ethanamide, CH3CONH2 (old name: acetamide).
 * Some simple amides**

The three simplest amides are:


 * HCONH2 || methanamide  ||
 * CH3CONH2 || ethanamide  ||
 * CH3CH2CONH2 || propanamide  ||

If the chain was branched, the carbon in the -CONH2 group counts as the number 1 carbon atom. For example:

Physical Properties of Amides: High melting point as they can form hydrogen bonds:
 * The hydrogen atoms in the -NH2 group are sufficiently positive to form a hydrogen bond with a lone pair on the oxygen atom of another molecule.

As the molecule has 2 H+ atoms and 2 lone pairs on the oxygen atoms, there is a large potential for more hydrogen bonds to form Soluble in water:
 * As have the ability to form hydrogen bonds with the water molecules

Making Amides From Carboxyllic Acids:
 * Carboxyllic acid is heated to an ammonium salt which gives off an amide. Salt formed by adding solid ammonium to the acid
 * For example, ammonium ethanoate is made by adding ammonium carbonate to an excess of ethanoic acid.

> > The presence of the excess ethanoic acid helps to prevent this from happening by moving the position of equilibrium to the left
 * When the reaction is complete, the mixture is heated and the ammonium salt dehydrates producing ethanamide.
 * Ethanoic acid excess is there to stop dissociation into a salt
 * Ammonium salts split into ammonia and the acid on heating. They recombine on cooling. if dissociation happened in this example, the ammonia would escape and it would not be able to re combine
 * The dissociation is reversible:

__Making Amides From Acyl Chlorides:__
 * Acid chlorides

You can think of the reaction as happening in two stages.
 * To make ethanamide from ethanoyl chloride, you normally add the ethanoyl chloride to a concentrated solution of ammonia in water. There is a very violent reaction producing lots of white smoke - a mixture of solid ammonium chloride and ethanamide. Some of the mixture remains dissolved in water as a colourless solution.
 * In the first stage, the ammonia reacts with the ethanoyl chloride to give ethanamide and hydrogen chloride gas.
 * Then the hydrogen chloride produced reacts with excess ammonia to give ammonium chloride.
 * . . . and you can combine all this together to give one overall equation:

__Making Amides From Acid Anhydrides:__ The products are very similar
 * Acid anyhdrides
 * The reactions of acid anhydrides are rather like those of acyl chlorides except that during their reactions, a molecule of carboxylic acid is produced rather than the HCl formed when an acyl chloride reacts.
 * If ethanoic anhydride is added to concentrated ammonia solution, ethanamide is formed together with ammonium ethanoate. Again, the reaction happens in two stages.
 * In the first stage, ethanamide is formed together with ethanoic acid.
 * Then the ethanoic acid produced reacts with excess ammonia to give ammonium ethanoate.
 * . . . and you can combine all this together to give one overall equation: