What Is Crotonic Acid?
Crotonic acid is an organic compound classified as a monounsaturated fatty acid.
Its molecular formula is C4H6O2, and it has one double bond in the molecule; its IUPAC nomenclature is (E)-but-2-enoic acid, and its CAS number is 107-93-7.
It is found in nature as the main component of hazel oil, and the name crotonic acid is also derived from the genus hazel. It has a molecular weight of 86.09, a melting point of 70-73°C, and a boiling point of 185-189°C. It is a white to yellow needle-like crystalline solid at room temperature.
It has a pungent odor similar to butyric acid. It has an acid dissociation constant pKa of 4.69 and a density of 1.02 g/cm3. The substance is soluble in a variety of organic solvents, including water, ethanol, and acetone.
Uses of Crotonic Acid
The main use of crotonic acid is as a raw material for copolymers, which is formed by copolymerization with other substances. Major copolymerization monomers include vinyl compounds, such as vinyl acetate. Synthesized copolymer compounds are used as film formers, adhesives, and hair styling agents.
Crotonic acid is also used in the copolymerization of crotonic acid hydrogel systems using gamma radiation. The cross-linked copolymer crotonic acid hydrogel is a substance that has been shown to be effective in slow-release fertilizers and drugs and in preventing environmental pollution.
Other applications include use as a raw material for various organic syntheses such as pharmaceuticals, fragrances, and agrochemicals.
Characteristics of Crotonic Acid
The double bond of crotonic acid has a trans structure. Crotonic acid has a geometric isomer with a cis double bond, called isocrotonic acid.
Isocrotonic acid is an isolable stable oily liquid with a boiling point of 171.9°C. It is isomerized to crotonic acid by the action of heat, light, or acid. Crotonic acid is a substance that may polymerize or be altered by the action of light or peroxides. It is advisable to store it in light-shielded containers.
Its flash point is 87.8℃ and its spontaneous combustion temperature is 396℃.
Types of Crotonic Acid
Crotonic acid is mainly sold as a reagent for synthetic organic chemical applications. The product is available in 25g, 500g, 3kg, and other capacities that are easy to handle in the laboratory. The reagent product can be stored at room temperature.
Other Information on Crotonic Acid
1. Synthesis of Crotonic Acid
Crotonic acid is industrially synthesized by the oxidation of crotonaldehyde. Other synthetic methods include the condensation reaction of acetaldehyde and malonic acid in the presence of a base.
2. Chemical Reaction of Crotonic Acid
Crotonic acid reacts with N-ethyl-o-toluidine as a raw material for crotonamidone. It is also a substance that undergoes a copolymerization reaction when reacted with vinyl compounds.
Other examples of chemical reactions include:
- Reduction of double bonds with zinc/sulfuric acid
- Addition reactions to double bonds with chlorine or bromine
- Formation reaction of 3-bromobutyric acid with hydrogen bromide
- Addition of hydroxyl groups under alkaline conditions with potassium permanganate
- Formation reaction of acid anhydride by heating with acetic anhydride, etc.
- Esterification reaction by reaction of alcohol and sulfuric acid
In addition, reaction to hypochlorous acid produces 2-chloro-3-hydroxybutyric acid. This substance is used in various reactions, such as butyric acid formation (reduction reaction) by sodium amalgam, dehydration reaction (double bond formation) by sulfuric acid, and epoxidation reaction by potassium ethoxide.
Crotonic acid poses a fire and explosion hazard when reacting violently with bases, oxidizing agents, and reducing agents. Although stable under normal storage conditions, it should not be mixed with bases, oxidizing agents, or reducing agents.