Polyyne

Some tiny things join in long lines.

These lines are found in many plants. You can find them in carrots and celery. They can even be found in space!

In plants, these lines can be a flavor. They can also be a way to stay safe. Some lines can even be a poison. They help the plant in different ways. It is amazing to see them in so many places!

Polyyne is a type of organic compound.

These are made of long chains of carbon atoms. The chains have a special pattern of single and triple bonds. Because of this pattern, the chains are very stiff. They can also carry electricity well. This might make them useful as tiny wires in the future.

Many living things make polyynes. You can find them in plants like carrots, celery, and parsley.

In these plants, they can create a bitter taste. Some polyynes act as toxins, which are substances that can be poisonous. For example, water hemlock contains poisons called oenanthotoxin and cicutoxin. Other plants, like the soldier beetle, use polyynes to stay safe from enemies.

Scientists also find polyynes in space. They have been seen in clouds of gas where hydrogen is hard to find.

Making long polyyne chains in a lab is hard. Long chains can be unstable and may even explode. To keep them safe, scientists often add bulky groups to the ends. These groups act like bumpers to keep the chains apart.

Polyyne is a special kind of organic compound made of carbon.

These molecules are built from long chains of carbon atoms. Inside these chains, the atoms connect using a pattern of single and triple bonds. This specific pattern makes the chains very stiff and rigid. They can also conduct electricity very well. Because of these traits, scientists think they could work as tiny wires in molecular nanotechnology.

Making these chains in a laboratory is a difficult task. Long polyyne chains are naturally unstable when they are gathered in large amounts. They can link together and release energy, which can cause explosions. To keep them safe, scientists use a trick called end-capping. They add bulky groups to the ends of the chains to act like bumpers. These bumpers keep the chains from touching each other. In 1995, researchers used this method to make carbyne chains with over 300 carbon atoms.

Humans have been studying these compounds for a long time. The first reported synthesis happened in 1869. A scientist named Marcellin Berthelot observed a reaction involving copper phenylacetylide. He saw that the substance changed when it met air. This created diphenylbutadiyne, which is a simple polyyne. Later, in 1971, T. R. Johnson and D. R. M. Walton found a way to protect the chains. They used special end-caps to grow chains up to 16 units long in a liquid solution.

Many different living things create polyynes for different reasons. In plants, they can act as colors, flavors, or even defenses. For example, the compound falcarindiol is what makes carrots taste bitter.

Some plants use them as toxins to stay safe. Water hemlock contains poisons called oenanthotoxin and cicutoxin.

Other plants, like the ichthyothere, have compounds that are toxic to fish. Even soldier beetles make a polyyne to defend themselves.

Polynes are not just found on Earth; they exist in deep space too. Scientists have detected certain polyyne radicals in interstellar molecular clouds. These are huge clouds of gas and dust far away from our planet. They are often found in places where hydrogen is very scarce. This shows that the same building blocks we see in a carrot can exist in the stars. It is amazing to think that these tiny, stiff chains are part of the wider universe.

A polyyne is a specific type of organic compound made of carbon atoms.

These molecules consist of a series of consecutive alkynes, which are carbon chains. They are defined by a repeating pattern of alternating single and triple bonds. This unique structure gives polyynes very specific physical properties. They are notably rigid, meaning the chains do not bend easily. They also possess high conductivity, which allows them to carry electricity. Because of these traits, scientists view them as promising candidates for use as wires in molecular nanotechnology.

Building these chains in a laboratory is a complex chemical process. Scientists often use acetylene homocoupling reactions to create them. Common methods include the Glaser coupling or the related Elinton and Hay protocols. Another method is the Cadiot–Chodkiewicz coupling, which unites two separate alkyne building blocks. To create the longest known phenyl end-capped polyynes, researchers used the elimination of chlorovinylsilanes. For the longest known polyyne, a step called the Fritsch–Buttenberg–Wiechell rearrangement was essential.

Research into polyyne length has grown significantly over the decades. In the 1950s, scientists synthesized chains with up to 4 or 5 units. Around 1971, T. R. Johnson and D. R. M. Walton improved this using end-caps. They used groups like ethyl to protect the chain during doubling reactions. This allowed them to reach 8 units in a pure state and 16 units in solution. Later, Tykwinski and colleagues reached lengths of C20. By 2010, the longest isolated polyyne had 22 acetylenic units, totaling 44 carbon atoms.

Stability is a major challenge when working with these molecules. Long polyyne chains are inherently unstable in bulk form. This is because they can cross-link with one another in an exothermic reaction. An exothermic reaction releases energy, which can make explosions a real hazard. To prevent this, scientists use bulky end-groups to keep the chains apart. Using groups like tert-butyl or trifluoromethyl can make them stable against moisture and oxygen. In 1995, researchers reported making carbyne chains with over 300 carbon atoms using this technique.

The physical shape of a polyyne can change based on its environment. In a crystalline solid state, long chains often form a curved or helical backbone. This happens because of crystal packing effects. For example, a polyyne with 8 units and a triisopropylsilyl cap shows a backbone bent by 25 to 30 degrees. This arching shape allows the molecules to pack more densely. In these cases, the distance between backbones is only 0.35 to 0.5 nm. This closeness is near the range where spontaneous cross-linking occurs.

Many organisms synthesize polyynes for biological functions. In plants, they serve as pigments, flavors, or chemical repellents. The sunflower, carrot, and ginseng families are known to contain them. For instance, the compound falcarindiol is found in carrots and celery. It is the main substance responsible for the bitter taste in carrots.

Other polyynes, like oenanthotoxin and cicutoxin, act as poisons in water hemlock. Some plants, such as the ichthyothere, produce ichthyothereol, which is toxic to fish and mammals.

Even soldier beetles produce dihydromatricaria acid for defense.

Beyond Earth, polyynes play a role in the chemistry of space. Scientists have detected octatetraynyl and hexatriynyl radicals in interstellar molecular clouds. These are vast regions of gas and dust in space. These molecules are often found in areas where hydrogen is very scarce. There have also been claims that polyynes exist in the mineral chaoite at astronomical impact sites on Earth. While some of these interpretations are contested, they show how these carbon chains connect biology, chemistry, and the wider universe.