What is aniline? Aniline is an organic compound that is classified as the simplest aromatic amine. The functional group of aniline is the amino group {eq}-NH_2 {/eq}. The amino group is the derivative of the chemical compound ammonia {eq}NH_3 {/eq}. This functional group consists of a nitrogen that is bonded with hydrogen atoms and a side chain R. The side chain can be an alkyl or an aryl group. The −NH2−NH2. The amino group is the derivative of the chemical compound ammonia NH3NH3. This functional group consists of a nitrogen that is bonded with hydrogen atoms and a side chain R. The side chain can be an alkyl or an aryl group. The molecular formula of aniline is {eq}C_6H_7N {/eq}. The Aniline formula can be reformatted as {eq}C_6H_5NH_2 {/eq} to show the functional group clearly. This compound is comprised of a total of six carbons bonding with five hydrogens and a nitrogen that is bonded with two hydrogens. The total number of atoms is as follows: C6H7NC6H7N. The Aniline formula can be reformatted as C6H5NH2C6H5NH2 to show the functional group clearly. This compound is comprised of a total of six carbons bonding with five hydrogens and a nitrogen that is bonded with two hydrogens. The total number of atoms is as follows:
- Six carbon atoms.
- Seven Hydrogen atoms.
- One nitrogen atom.
Aniline has multiple aliases; the following are the other names it goes by:
- Phenylamine.
- Aminobenzene.
- Benzenamine.
- Its CAS (Chemical Abstract Services) registry no. is 62-53-3.
Molecular Weight & Properties of Aniline
Aniline is a colorless liquid with an odor that resembles rotten fish. Its molecular weight is estimated to be equal to 93.13 g/mol. This aromatic compound is classified as flammable and highly toxic. The following table summarizes the important properties of aniline.
The amine group is generally basic, but the basicity of aniline is quite low when compared to aliphatic amines. The reason behind this is linked to resonance, which is defined as the delocalization of electrons from location to another. Figure 6 shows all the possible resonance structures where the nitrogen atom forms a double bond with the carbon atom.
Aniline Functional Group
As mentioned earlier, the aniline functional group is the amino group −NH2−NH2. The structure of the amino group is planar. That is because the hybridization of the nitrogen atom in the group is sp2sp2. The N’s lone electron pairs is in the p orbital, which makes it capable of delocalizing into the benzene ring. This is the case for the amino group when it is attached to a phenyl group. When the amino group is attached to an aliphatic compound like methylamine, its nitrogen exhibits a sp3sp3 hybridization. This gives methylamines a pyramidal geometry.
As a general rule of thumb, the C-N bond length in aromatic amines is shorter than that in aliphatic amines. The reason behind this is linked to resonance; in one of aniline’s resonance structures the nitrogen atom forms a double bond with one of the carbons in the ring. The bond length of atoms forming covalent bonds is shorter than those that form single bonds. Comparing the bond length between aniline and cyclohexylamine, it can be deduced that the C-N in the former is shorter than the latter because of nitrogen’s ability to form a double bond with carbon when the electrons are delocalizing.
