Which of the following will not be soluble in sodium bicarbonate? (a) Benzenesulphonic acid (b) Benzoic acid (c) \(2,4,6\) -trinitrophenol (d) O-nitrophenol

Understanding acidity and basicity is crucial when it comes to solubility, especially in the context of organic compounds interacting with bases such as sodium bicarbonate. At its core, acidity refers to the propensity of a molecule to donate a proton (hydrogen ion), while basicity pertains to the molecule's ability to accept a proton.

Acids and bases react with each other in a neutralization reaction, where the acid donates a proton to the base. This reaction is essential in predicting whether a substance will be soluble in a basic solution like sodium bicarbonate. For example, sodium bicarbonate, acting as a moderate base, can only react with substances that are sufficiently acidic — stronger acids than itself. This ability to either donate or accept a proton is quantified by the acid dissociation constant, or pKa, which allows chemists to predict the solubility of compounds in various solutions based on their acidity or basicity levels.

The solubility of organic compounds in different solvents depends on the molecular structure and the functional groups present. Solvents like sodium bicarbonate, which have basic characteristics, selectively dissolve compounds based on their acidic properties. Organic acids typically have a hydrogen atom bonded to an oxygen (as in a carboxylic acid) or to a sulfur (as in a sulphonic acid).

When an organic acid is introduced to sodium bicarbonate, it may undergo a chemical reaction if the acid is strong enough, forming water and carbon dioxide gas as byproducts. This reaction not only indicates the strength of the acid but also results in increased solubility due to the formation of soluble ionic salts. In contrast, organic compounds with weak acidity or neutral properties often remain insoluble in a basic solution like sodium bicarbonate, leading to distinct solubility behaviors observable in the laboratory.

Chemical reactions are the backbone of organic chemistry, allowing for the transformation of substances through the making and breaking of chemical bonds. Reactions between acids and bases, such as the ones involving sodium bicarbonate, are just one type of chemical reaction prevalent in organic chemistry. These acid-base reactions are special because they can provide insight into the nature of the substances involved.

Reactions that produce gas, such as carbon dioxide from the reaction between sodium bicarbonate and an acid, are particularly useful as indicators of solubility. This type of reaction not only shows the reaction has occurred but also can serve as a qualitative test for the strength of an acid in organic compounds. Understanding these reactions enhances a chemist's ability to predict product formation and the conditions necessary for various compounds' solubility and reactivity.