Prototropy

Before we discuss what prototropy is, we must be aware of tautomerism, the process known as tautomerization. This process is a key concept of organic chemistry which is concerned with the interconversion of different types of compounds by the process of relocation of an atom or chemical bond under suitable conditions. This is essentially a type of chemical reaction where the exchange or reallocation of hydrogen atoms of two forms of atoms or the separation of single or double bonds or maybe its rapid formation can be witnessed. The idea of relocation of the chemical bonds of the atoms can be essentially the hydrogen atom exchange process between the two concerned forms of atoms. 

This type of tautomerism is caused by the acid-base behaviour of the compound and in this type of tautomerism, the two forms are only different in the proton’s position. This particular structure has the same empirical formula and the same number of charges. This type of tautomerism is the most common type of tautomerism and in this process, one isomer is converted into another by the alteration or relocation of the atoms or bonds which must be a proton. This method is also popularly known as prototropic-tautomerism. This method can be further divided into two other types of tautomerism namely; the annular tautomerism and the ring-chain tautomerism.

Prototropy and its forms 

As mentioned earlier, prototropy is the most common form of tautomerism. This process can be further divided into two more types. Let us understand all the different types of tautomerism and how they differ from one another:

• Prototropy- This type of tautomerism is caused by the acid-base behaviour of the compound and in this type of tautomerism, the two forms are only different in the proton’s position. This particular structure has the same empirical formula and the same number of charges. One isomer is converted into another isomer by the simple chemical process of reallocation of the atoms or chemical bonds.

1. Annular Tautomerism- If a situation occurs when a proton is seen to be occupying two or more two positions of a heterocyclic system, it will be known as annular tautomerism. If an open structure is altered to a ring-like structure due to the delocalization of the protons, then it will be known as a ring-chain tautomer. Glucose is a great example of a ring-chain tautomer. 

2. Valence Tautomerism- This is a type of tautomerism where there is a continuous process of formation and both single and double bonds are continuing to break in the compound without any atoms or groups migrating. This is a very rapid process and is much different from other types of tautomerism. 

Protonation Process

Protonation which is also popularly known as hydronation is the process where a proton is added to an atom, ion, or molecule and as a result of that, a conjugate acid is formed which means a leftover acid from which a proton has been removed after the same acid had donated a proton for the chemical reaction.

Empirical Formula

Definition

In chemistry, when a chemical compound is considered, the empirical formula will be the simplest whole-number ratio of the number of atoms that are present in that concerned compound. 

Formula

To figure out the empirical formula of a compound, firstly, the percentage of the mass of the elements in the compound needs to be known and then the percentage should be converted into the unit grams. After converting the mass percentage into grams, all the masses require to be divided by their respective molar masses. Now, from the previous step, the smallest answer in moles will be taken and all the answers will be divided by that (smallest) number. It must be remembered that the smallest number taken can be rounded off to get the nearest whole number. Finally, the subscripts of the chemical formula will be the coefficients that were calculated in the previous step. 

Conclusion

The process of prototrophy is the most common form of tautomerism and it can be further divided into ring-chain tautomerism and annular tautomerism respectively. The chemical reactions can be divided into these different types by detecting the movement and relocation of the chemical bonds or atoms in the concerned molecules. Coming back to tautomerism, which is the broader idea in this chapter, it is a phenomenon where a single chemical compound is found to be existing in two or more structures and that structure is interconvertible.