INTRODUCING NITRILES   This page explains what nitriles are and looks at their simple physical properties such as solubility and boiling points. What are nitriles? Nitriles contain the -CN group, and used to be known as cyanides. Some simple nitriles The smallest organic nitrile is ethanenitrile, CH3CN, (old name: methyl cyanide or acetonitrile - and sometimes now called ethanonitrile). Hydrogen cyanide, HCN, doesn't usually count as organic, even though it contains a carbon atom. Notice the triple bond between the carbon and nitrogen in the -CN group. The three simplest nitriles are: CH3CN ethanenitrile CH3CH2CN propanenitrile CH3CH2CH2CN butanenitrile When you are counting the length of the carbon chain, don't forget the carbon in the -CN group. If the chain is branched, this carbon usually counts as the number 1 carbon.
	Note:  Compounds like this are formed when aldehydes react with hydrogen cyanide. This is therefore the sort of branched nitrile that you are most likely to come across at this level.
Physical properties Boiling points The small nitriles are liquids at room temperature. nitrile boiling point (°C) CH3CN 82 CH3CH2CN 97 CH3CH2CH2CN 116 - 118
	Note:  The majority of the data sheets I have looked at quote this boiling range for butanenitrile. I don't know why it doesn't seem to have a precise boiling point.
These boiling points are very high for the size of the molecules - similar to what you would expect if they were capable of forming hydrogen bonds. However, they don't form hydrogen bonds - they don't have a hydrogen atom directly attached to an electronegative element. They are just very polar molecules. The nitrogen is very electronegative and the electrons in the triple bond are very easily pulled towards the nitrogen end of the bond. Nitriles therefore have strong permanent dipole-dipole attractions as well as van der Waals dispersion forces between their molecules.
Solubility in water Ethanenitrile is completely soluble in water, and the solubility then falls as chain length increases. nitrile solubility at 20°C CH3CN miscible CH3CH2CN 10 g per 100 cm3 of water CH3CH2CH2CN 3 g per 100 cm3 of water The reason for the solubility is that although nitriles can't hydrogen bond with themselves, they can hydrogen bond with water molecules. One of the slightly positive hydrogen atoms in a water molecule is attracted to the lone pair on the nitrogen atom in a nitrile and a hydrogen bond is formed. There will also, of course, be dispersion forces and dipole-dipole attractions between the nitrile and water molecules. Forming these attractions releases energy. This helps to supply the energy needed to separate water molecule from water molecule and nitrile molecule from nitrile molecule before they can mix together. As chain lengths increase, the hydrocarbon parts of the nitrile molecules start to get in the way. By forcing themselves between water molecules, they break the relatively strong hydrogen bonds between water molecules without replacing them by anything as good. This makes the process energetically less profitable, and so solubility decreases. MECHANISM OF THE ACID catalyzed HYDROLYSIS OF NITRILES Step 1: An acid/base reaction. Since we only have a weak nucleophile so activate the nitrile, protonation makes it more electrophilic. Step 2: The water O functions as the nucleophile attacking the electrophilic C in the CºN, with the electrons moving towards the positive center.  Step 3: An acid/base reaction. Deprotonate the oxygen that came from the water molecule. The remaining task is a tautomerization at N and O centers. Step 4: An acid/base reaction. Protonate the N gives us the -NH2 we need....  Step 5: Use the electrons of an adjacent O to neutralise the positive at the N and form the p bond in the C=O.  Step 6: An acid/base reaction. Deprotonation of the oxonium ion reveals the carbonyl in the amide intermediate....halfway to the acid.....  What about the rest ?

WHAT IS LACTAM ?

before discussing the lactam, I will repeat a bit about the Amide.

Amides

An amide may be produced by combining a carboxylic acid with an amino group. In addition to amide formation, a molecule of water is related. For example, ethyl amine reacts with acetic acid to form ethyl acetamide and water.

CH₃CH₂-NH₂ + HOOC-CH₃ → CH₃CH₂-NH-OC-CH₃ + HOH

Notice that, in this instance, two short-chain compounds react to form a longer-chain compound.¹The result is called an amide.

Lactams - Cyclic Amides

With some modification, a reaction may be carried out that generates a ring structure containing a similar linkage. Consider the result if two functional groups are a distance apart on the same molecule and react together. Consider, for instance, 4-aminobutyric acid, H₂N-CH₂CH₂CH₂-COOH. If reacted utilizing the proper conditions,²

H₂N-CH₂CH₂CH₂-COOH → 5-member ring + HOH (see associated image).

The amino group at one end reacts with the carboxylic acid group at the other, closing the molecule to form the ring. The ring structure is called a lactam. The type of lactam is designated by using a Greek letter prefix that indicating the number of carbons in the ring, not counting the carbonyl group. For instance, if there are two such carbons, the prefix is beta (the 2nd letter of the alphabet)-if there are four, the prefix is delta, and so on. The ring formed in the above reaction is a gamma-lactam. It's name is based on the number of carbon atoms in the skeleton-in this instance, butyrolactam. There are other ways of naming the structure, one of which is 2-pyrollidinone.

Reducing the Carbonyl in Lactam to CH2

The carbonyl of a lactam can be reduced to produce a heterocyclic ring. "Heterocyclic" refers to the presence of a non-carbon atom in the ring. It is thus easy to produce a four member ring containing a nitrogen atom, or a five member ring, a six member ring, and so on. Such rings often occur in very important organic compounds related to living things. There are heterocyclic rings in the active ingredients of a plethora of medications. There are a variety of methodologies for reducing the carbonyl. To visualize the end result, again refer to the image associated with this article.

¹ Although it isn't obvious as drawn, the carbon-containing chain formed actually consists of six atoms, C-C-C-N-C-C. The oxygen is actually attached to the next-to-last carbon by a double-bond off to the side. 

² Utilizing different conditions can produce a polymeric product. The amino group of one molecule would react with the carboxylic acid of a different molecule, and so on.

one of example from lactams is beta-lactam

amide bond

Amide can also refer to a conjugate base of ammonia and an organic amine, represented as anions R₂N^–. For discussion of these "anionic amides," see the articles sodium amide and lithium diisopropilamide.

The simplest amides are derivatives of ammonia wherein one hydrogen atom has been replaced by an acyl group. The ensemble is generally represented as RC(O)NH₂. Closely related and even more numerous are amides derived from primary amines (R'NH₂) with the formula RC(O)NHR'. Amides are also commonly derived from secondary amides (R'RNH) with the formula RC(O)NR'R. Amide are usually regarded as derivatives of carboxylic acid in which the hydroxil group has been replaced by an amine or ammonia.

Properties

Basicity

Compared to amines, amides are very weak bases. While the conjugate acid of an amines has a pKa of about 9.5, the conjugate acid of an amide has a pKa around -0.5. Therefore amides don't have as clearly noticeable acid-base properties in water. This lack of basicity is explained by the electron-withdrawing nature of the carbonyl group where the lone pair of electrons on the nitrogen is delocalized by resonance. On the other hand, amides are much stronger bases than carboxylic, esters, aldehyde, and ketones (conjugated acid pKa between -6 and -10). It is estimated in silico that acetamide is represented by resonance structure A for 62% and by B for 28%. Resonance is largely prevented in the very strained quinuclidone.

Because of the greater electronegativity of oxygen, the carbonyl (C=O) is a stronger dipole than the N-C dipole. The presence of a C=O dipole and, to a lesser extent a N-C dipole, allows amides to act as H-bond acceptors. In primary and secondary amides, the presence of N-H dipoles allows amides to function as H-bond donors as well. Thus amides can participate in hydrogen bonding with water and other protic solvents; the oxygen atom can accept hydrogen bonds from water and the N-H hydrogen atoms can donate H-bonds. As a result of interactions such as these, the water solubility of amides is greater than that of corresponding hydrocarbons.

The proton of a primary or secondary amide does not dissociate readily under normal conditions; its pK_a is usually well above 15. Conversely, under extremely acidic conditions, the carbonyl oxygen can become protonated with a pK_a of roughly –1.

Solubility

The solubilities of amides and esters are roughly comparable. Typically amides are less soluble than comparable amines and carboxylic acids since these compounds can both donate and accept hydrogen bonds. Tertiary amides, with the important exception of N,N-dimethylformamide, exhibit low solubility in water.

Characterization

The presence of the functional group is generally easily established, at least in small molecules. They are the most common non-basic functional group. They can be distinguished from nitro and cyano groups by their IR specta. Amides exhibit a moderately intense ν_CO band near 1650 cm⁻¹. By ¹H NMR spectroscopy, CONHR signals occur at low fields. In X-ray crystallography, the C(O)N center together with the three immediately adjacent atoms characteristically define a plane.

Applications and occurrence

Amides are pervasive in nature and technology as structural materials. The amide linkage is easily formed, confers structural rigidity, and resists hydrolisis. Nylons are polyamides as are the very resilient materials Aramid, Twaron, and Kevlar. Amide linkages in a biochemical context are called peptide linkage. Amide linkages constitute a defining molecular feature of proteins, the secondary structure of which is due in part to the hydrogen bonding abilities of amides. Low molecular weight amides, such as dimethylformamide (HC(O)N(CH₃)₂), are common solvents. Many drugs are amides, including penicilin and LSD.

Amide synthesis

Amides are commonly formed via reactions of a carboxylic acid with an amine. Many methods are known for driving the unfavorable equilibrium to the right:

RCO₂H + R'R"NH  RC(O)NR'R" + H₂O

For the most part, these reactions involve "activating" the carboxylic acid and the best known method, the Schotten-bouman reaction, which involves conversion of the acid to the acid chlorides.