AMIDE

AMIDE

Amide is a compound that is not reactive, since the protein consists of amino acids linked by amide bonds. Amide does not react with the halide ion, carboxylate ion, alcohol, or water because in each case, the incoming nucleophile is a weak base of the amide group to go.
 
Amide can react with water and alcohol if the reaction mixture is heated under acidic conditions.



 
Molecular orbital theory can explain why the amide is not reactive. Amide has an important resonance contributor in which shares one pair of nitrogen with the carbonyl carbon, which contains a lone pair orbital overlap of the empty orbital of the carbonyl group.

 
Lower energy state overlap-one partner is not a base or nucleophilic, and raises the energy of the orbital of the carbonyl group, making it less reactive toward nucleophiles. Amide NH 2 groups can be dehydrated to a nitrile. Dehydrating reagents commonly used for this purpose is P2O5, POCl3, and SOCl3.

 

Hydrolysis of amides with acid catalyst

When the amide is hydrolyzed in acidic conditions, acid proton of the carbonyl oxygen, increase the susceptibility of the carbonyl carbon to nucleophilic attack. Nucleophilic attack by water on the carbonyl carbon causes the tetrahedral intermediate compound I, which is in equilibrium with form rather than protons, tetrahedral intermediate II. Reprotonasi can occur either at the tetrahedral intermediates of oxygen to reform the I or the nitrogen to form a tetrahedral intermediate III. Protonation at nitrogen is preferred because the NH2 group is a stronger base than OH groups. Of the two possible groups to go on a tetrahedral intermediate III group (-OH and NH3), NH3 is a weak base, so it is released, forming carboxylic acids as end products. Because the reaction is carried out in acid solution, NH3 be protonated after expelled from the tetrahedral intermediates. This prevents the reverse reaction.
Mechanism of hydrolysis of amides with acid catalyst:
 

CHEMISTRY INORGANIC II

LACTAM

From left to right, general structures of a β-lactam, a γ-lactam, a δ-lactam and a ε-lactam.

A lactam (the noun is a portmanteau of the words lactone + amide) is a cyclic amide. Prefixes indicate how many carbon atoms (apart from the carbonyl moiety) are present in the ring: β-lactam (2 carbon atoms outside the carbonyl, 4 ring atoms in total), γ-lactam (3 and 5 total), δ-lactam (4 and 6 total). Beta β, gamma γ and delta δ are the second, third and fourth letters in the alphabetical order of the Greek alphabet, respectively.

         Synthesis

General synthetic methods exist for the organic synthesis of lactams.

• Lactams form by the acid-catalyzed rearrangement of oximes in the Beckmann rearrangement.
• Lactams form from cyclic ketones and hydrazoic acid in the Schmidt reaction.
• Lactams form from cyclisation of amino acids.
• In iodolactamization  an iminium ion reacts with an halonium ion formed in situ by reaction of an alkene with iodine.

• Lactams form by copper catalyzed 1,3-dipolar cycloaddition of alkynes and nitrones in the Kinugasa reaction
• Diels-Alder reaction between cyclopentadiene and chlorosulfonyl isocyanate (CSI) can be utilized to obtain both β- as well as γ-lactam. At lower temp (−78 °C) β-lactam is the preferred product. At optimum temperatures, a highly useful γ-lactam known as Vince Lactam is obtained.