Yes, butanoic acid is completely miscible in water. This means it dissolves fully in water, regardless of the proportion of butanoic acid to water, forming a homogeneous solution.
Butanoic acid, also known as butyric acid, is a carboxylic acid with a relatively short carbon chain (four carbons). Its strong affinity for water makes it highly soluble, contrasting with compounds like ethyl acetate, which has a solubility of 8.3 g per 100 ml of water.
Why is Butanoic Acid So Soluble in Water?
The exceptional solubility of butanoic acid in water is primarily due to its ability to form strong hydrogen bonds with water molecules.
- Polar Carboxyl Group: The -COOH (carboxyl) group in butanoic acid is highly polar. Both the oxygen atoms in the carboxyl group can act as hydrogen bond acceptors, and the hydrogen atom attached to the oxygen can act as a hydrogen bond donor.
- Interaction with Water: Water molecules are also highly polar and form extensive hydrogen bond networks. Butanoic acid can readily integrate into this network by forming hydrogen bonds with water molecules, disrupting water's own hydrogen bonding and forming new, stable bonds with water.
- Short Hydrocarbon Chain: While the hydrocarbon chain (the non-polar part) of butanoic acid is present, it is short (CH₃CH₂CH₂-). For short-chain carboxylic acids, the strong polar interactions of the carboxyl group outweigh the hydrophobic effects of the small hydrocarbon portion, leading to high solubility. As the hydrocarbon chain lengthens, the solubility in water generally decreases.
Properties of Butanoic Acid
Butanoic acid is an important compound found naturally in milk, especially butter, and is responsible for the characteristic odor of rancid butter.
| Property | Value |
|---|---|
| Chemical Formula | C₄H₈O₂ or CH₃CH₂CH₂COOH |
| Molar Mass | 88.11 g/mol |
| Appearance | Colorless, oily liquid |
| Odor | Unpleasant, rancid butter-like odor |
| Solubility in Water | Completely Miscible |
| Density | 0.96 g/cm³ at 20 °C |
| Melting Point | -5.3 °C (22.5 °F) |
| Boiling Point | 163.5 °C (326.3 °F) |
For more detailed chemical and physical properties, you can refer to resources like PubChem's Butanoic Acid page.
Practical Implications
The complete miscibility of butanoic acid in water is significant in various contexts:
- Food Chemistry: Its presence and solubility in water-based food systems impact flavor and preservation.
- Biological Systems: Butanoic acid is a short-chain fatty acid produced in the gut by beneficial bacteria and is readily absorbed and transported throughout the body due to its water solubility.
- Industrial Applications: Its solubility allows for its use in various industrial processes, including the production of esters for artificial flavors and fragrances, where its ability to mix with water-based reactants is crucial.
Understanding the solubility of compounds like butanoic acid is fundamental in chemistry, allowing for predictions about their behavior in different solvents and their roles in biological and industrial processes.
