Question

What is a solventless process?

Answer 1

Hint: A solvent is any substance that gives a medium for the reaction to occur. The name solventless itself determines a process that will have no solvent. For a process to be solventless, the reactants can substitute as solvents or the reaction can be dry.

Complete answer:
In a solventless process, there is no presence of any solvent. This process is also termed the solid-state chemical reaction or dry media chemical reaction. The reactant is also not in the liquid phase. Here, the reactant can be used alone or they can be combined with silica, clays, alumina, zeolites, or other substances having high stereoselectivity. This will reduce the formation of by-products and facilitate the rate of the reaction.
A solventless process can be completely dry or one of the reactants can act as a solvent. The latter is chemically known as ‘Neat reaction’. In a neat process, there is only a liquid phase which is not a solvent. There is even an absence of initiators or catalysts. Hydrogen peroxide or acetic acid can be a part of the neat reaction.
Example of solventless reaction:
The Knoevenagel condensation of ketones is by far the truly solventless reaction. The reactants are present in the ratio of 1:1 and are exposed to radiation in a hot oven.
Some substances like hash oil, paint, and epoxy contain very less amount of solvent. They contain no water or any solvent to dilute the reaction mixture.

Note:
Solventless reactions are more efficient as they give more selectivity. Also, they are eco-friendly and reduce pollution to quite an extent. They are more economic and most importantly they provide a high reaction rate due to the increased concentration of the reactants.