What Fats Have Triple Bonds? Exploring Rare Acetylenic Fatty Acids

January 5, 2026 •

4 min read

While most unsaturated fats contain double bonds, a special and rare class of lipids known as acetylenic fatty acids contains one or more carbon-carbon triple bonds in their structure. These unique molecules are not commonly found in the human diet but exist naturally in specific plants, fungi, and marine organisms.

Quick Summary

Acetylenic fatty acids are a rare class of lipids defined by the presence of carbon-carbon triple bonds, distinguishing them from common mono- or polyunsaturated fats. They are sourced from specific natural origins, including certain mosses and seed oils.

Key Points

Triple Bonds are Rare: Only a specialized class of lipids, acetylenic fatty acids, contains carbon-carbon triple bonds.
Not Found in Common Diet: These triple-bonded fats are not a standard part of the human diet, unlike omega-3 and omega-6 fatty acids.
Sources are Specific: Natural sources of acetylenic fats include particular seed oils (like sandalwood oil) and certain mosses and fungi.
Structure is Linear at Triple Bond: Unlike the kinks caused by cis double bonds, a triple bond creates a more linear and rigid section in the fatty acid chain.
Unique Biological Roles: Due to their distinct structure, acetylenic fatty acids often have unique biological properties, including antimicrobial effects.
Used in Research: Synthetic versions, like ETYA, are utilized in laboratory settings to inhibit metabolic pathways for scientific study.

Understanding Unsaturated Fats

To understand fats with triple bonds, it's essential to first grasp the basics of unsaturated fats. Fatty acids are organic molecules with a hydrocarbon chain and a carboxyl group. Saturated fatty acids contain only single bonds between their carbon atoms, making them 'saturated' with hydrogen. In contrast, unsaturated fatty acids have at least one carbon-carbon double or triple bond. These bonds create 'kinks' or rigidity in the molecule's shape, influencing its physical properties, such as being liquid at room temperature.

Most people are familiar with two main types of unsaturated fatty acids: monounsaturated fatty acids (MUFAs), which have one double bond, and polyunsaturated fatty acids (PUFAs), which have two or more double bonds. Acetylenic fatty acids represent a third, much rarer category of unsaturated fats, characterized by their triple bonds.

The Unique World of Acetylenic Fatty Acids

Acetylenic fatty acids, also known as alkynoic acids, are defined by the presence of one or more carbon-carbon triple bonds within their hydrocarbon chain. This triple bond, which is stronger and shorter than a single or double bond, gives these molecules distinct chemical properties. They are significantly rarer than other fatty acids and have different biological roles.

Examples of Acetylenic Fatty Acids and Their Sources

This unique class of lipids includes several notable examples found in nature:

Tariric Acid: A C18 fatty acid containing a triple bond at the 6th carbon from the methyl end. It is found predominantly in the seed oil of the tallow-wood tree, Ximenia americana, and other plants.
Crepenynic Acid: This C18 fatty acid features both a double bond and a triple bond. It is present in the seed oils of certain plants like Afzelia cuanzensis and Atractylodes lancea.
Santalbic Acid (Ximenynic Acid): Found in the seed oil of Santalum album (Indian sandalwood), this C18 acid contains a conjugated system of one double and one triple bond.
Polyacetylenic Acids: Some species, particularly certain fungi like Actinomycetes and marine sponges, produce more complex versions with multiple triple bonds, such as mycomycin and haliclonyne.
Moss Lipids: Specific mosses, including Fontinalis antipyretica, have also been found to synthesize acetylenic fatty acids.

Biological Roles and Applications

Unlike the widespread energy storage and cell membrane functions of common fats, acetylenic fatty acids often have more specialized biological roles. Some exhibit antimicrobial, fungicidal, or cytotoxic properties, serving as defensive compounds for the organisms that produce them. Others are used in scientific research as metabolic inhibitors. For instance, 5,8,11,14-eicosatetraynoic acid (ETYA) is a synthetic triple-bonded fatty acid used to inhibit metabolic pathways.

Comparison of Fatty Acid Types


Feature	Saturated Fats	Common Unsaturated Fats (Omega-3/6)	Acetylenic Fatty Acids
Bond Type	Single (C-C) only	Double (C=C) bonds	Triple (C≡C) bonds, often with double bonds
Chemical Structure	Straight, allowing for tight packing	Kinked at each double bond (cis configuration)	Linear geometry around the triple bond
Physical State	Solid at room temperature (e.g., butter)	Liquid at room temperature (e.g., olive oil)	Can vary, often liquid, but with unique reactivity
Dietary Importance	Excessive intake is linked to health risks	Essential for human health, widely consumed	Rare in human diet; specialized roles
Natural Sources	Animal products, tropical oils	Fish, nuts, seeds, plant oils	Rare seed oils, mosses, fungi, marine sponges
Melting Point	High	Low	Varies, but generally low

Chemical Properties of the Triple Bond

The presence of a triple bond drastically alters the molecule's chemical characteristics. A triple bond consists of one sigma bond and two pi bonds, creating a linear, rigid structure at that part of the molecule. This rigidity and high electron density make acetylenic fatty acids more reactive in some chemical processes compared to standard unsaturated fats. They can undergo unique reactions, such as hydrogenation, that can be exploited for specific applications. For instance, chemists have developed methods using mass spectrometry to precisely locate triple bonds in fatty acid chains, which is critical for structural characterization. For more on the chemical properties of unsaturated fats, including the common omega fatty acids, visit the Linus Pauling Institute website.

Conclusion

While most common fats are composed of saturated or double-bonded unsaturated fatty acids, the world of lipid chemistry holds a fascinating, lesser-known class: acetylenic fatty acids. Distinguished by their unique triple carbon-carbon bonds, these lipids are rarely found in the human diet. Their natural presence in specific plants, mosses, and marine life gives them specialized biological functions, from antimicrobial defense to potential medical applications. The existence of these triple-bonded fats showcases the incredible diversity and complexity of chemical structures found in living organisms, extending far beyond the typical fat molecules we encounter daily.

Frequently Asked Questions

No, acetylenic fatty acids are very rare in the typical human diet. They are mainly found in specific, less common natural sources like certain seed oils, mosses, and fungi, and are not part of major dietary fat intake.

Acetylenic fatty acids are predominantly found in the seed oils of specific plants, such as the sandalwood tree (Santalum album) and certain moss species. They are also produced by some fungi and marine invertebrates like sponges.

A triple bond makes a portion of the fatty acid chain more linear and rigid, unlike the 'kinks' typically produced by the cis configuration of double bonds in common unsaturated fats. The triple bond is also shorter and stronger than a double or single bond.

No, omega-3 and omega-6 fatty acids contain only double bonds, not triple bonds. These common polyunsaturated fats are characterized by the position of their double bonds relative to the molecule's methyl end.

Specific examples include tariric acid, found in the tallow-wood tree; crepenynic acid, found in certain plant seeds; and santalbic acid, which is abundant in sandalwood oil.

Acetylenic fatty acids often have defensive roles in the organisms that produce them. They can exhibit antimicrobial, fungicidal, or other cytotoxic effects, protecting the organism from pathogens. Some are also used as experimental metabolic inhibitors.

Yes, some triple-bonded fatty acids have been synthesized in labs. One example is 5,8,11,14-eicosatetraynoic acid (ETYA), which is used in scientific research to study metabolic pathways.

The significance of acetylenic fatty acids lies in their unique chemistry and biological activity. They highlight the vast diversity of lipid structures beyond common dietary fats and offer potential for specialized applications, such as in medicine and chemical research.