Question

Butanoic acid (also called butyric acid), \(\mathrm{HC}_{4} \mathrm{H}_{7} \mathrm{O}_{2},\) gives rancid butter its bad odor. What is the name of the salt \(\mathrm{NaC}_{4} \mathrm{H}_{7} \mathrm{O}_{2} ?\)

Short answer

The name of the salt \(\mathrm{NaC}_{4} \mathrm{H}_{7} \mathrm{O}_{2}\) is sodium butanoate.

Step-by-step solution

Identify the Acid and its Corresponding Salt

To name the salt, first identify the acid from which the salt is derived. Here, butanoic acid (butyric acid) is the acid. The general formula for a salt derived from an acid is written as the cation from the base, followed by the anion from the acid.

Determine the Cation

The cation comes from the base that reacts with the acid to form the salt. The given salt has sodium (Na), which indicates that sodium hydroxide (NaOH) is the base that reacted with butanoic acid.

Replace the Acid's Hydrogen with the Cation

In the salt \(\mathrm{NaC}_{4} \mathrm{H}_{7} \mathrm{O}_{2}\), the hydrogen (H) from the butanoic acid's carboxyl group \(\mathrm{HC(O)OH}\) has been replaced by the sodium cation (Na).

Name the Anion

The anion derives its name from the acid. The 'ic' ending of the acid is replaced by 'ate' for the anion. Therefore, the anion derived from butanoic acid will be called butanoate.

Combine the Cation and Anion Names

Combine the name of the cation and the anion to form the name of the salt. Sodium is the name of the cation and butanoate is the name of the anion. The full name of the salt is sodium butanoate.

Key concepts

Understanding Butanoic Acid

Butanoic acid, which is also known by the name butyric acid, is an organic compound that is well-known for giving rancid butter an unpleasant odor. Its chemical formula is represented as \(\mathrm{HC}_{4} \mathrm{H}_{7} \mathrm{O}_{2}\). This compound belongs to the class of carboxylic acids, characterized by the presence of a carboxyl group \(\mathrm{COOH}\). In its structure, butanoic acid possesses a four-carbon chain, with the carboxyl group attached at the end.

When we delve into its naming, 'butan' indicates the presence of a four-carbon alkyl chain, while the suffix '-oic acid' is indicative of a carboxylic acid. This acid is known for its role in various biochemical processes and industrial applications, such as the production of esters for fragrances or as an intermediate in the manufacturing of plasticizers.

Carboxylate Salts Formation

Carboxylate salts are formed from the neutralization of carboxylic acids by bases. This acid-base reaction results in a salt and water. In the context of butanoic acid reacting with sodium hydroxide (NaOH), the hydroxide ion \(\mathrm{OH^{-}}\) from NaOH reacts with the hydrogen from the carboxyl group of butanoic acid, leading to the formation of water and sodium butanoate, the sodium salt of butanoic acid.

The general structure of a carboxylate salt can be given as \(\mathrm{RCO_2}^- \mathrm{M^+}\), where R stands for the hydrocarbon chain, M represents a metal cation such as sodium (Na), and \(\mathrm{RCO_2}^-\) is the carboxylate anion. These salts are important in various industries for their use as soaps and detergents due to their surfactant properties.

Acid-Base Reactions in Carboxylate Salt Formation

Acid-base reactions are a cornerstone of chemistry, where an acid donates a proton (H+) and a base accepts it. In the formation of carboxylate salts, the reaction between a carboxylic acid and a base follows this same principle. The base, commonly a hydroxide (OH-) donor like sodium hydroxide, neutralizes the carboxylic acid, leading to the exchange of a hydrogen ion from the acid with a metal cation from the base.

In this neutralization, we observe the acid's hydrogen being replaced by the metal cation, forming the corresponding carboxylate salt. The reaction not only results in the salt but also water as a by-product, which is a testament to the H+ from the acid combining with the OH- of the base to form H2O. Understanding these reactions is crucial for students, as they lay the foundation for predicting the outcome of mixing acids and bases and have practical applications in various fields, including pharmaceuticals and chemical manufacturing.