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Chemistry of Agent Orange

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Chemistry Connections

The History & Chemistry of Agent Orange

Episode #14

Welcome to Chemistry Connections, my name is Zoey and I am your host for episode #14 called The History & Chemistry of Agent Orange. Today I will be discussing The notorious herbicides used during the Vietnam War, its composition, and its impact.

Segment 1: Introduction to Agent Orange

We’ll first start by introducing the herbicide, agent orange and its history and use during the Vietnam War.

Agent Orange was a mix of two herbicides which was sprayed in high concentrations during the Vietnam War by the U.S. Military. The name came from the orange stripe that was found on the containers of this chemical.
Agent Orange, and other herbicides known as the “rainbow herbicides,” were part of a large operation, operation Ranch Hand, which aimed to defoliate lots of land through spraying chemical herbicides from aircrafts. Agent Orange was the most used herbicide during the Vietnam War.
The chemical was sprayed in up to 20 times higher concentration than suggested for killing plants normally by manufacturers. This caused severe damage to millions of acres of forest, affected three million Vietnamese people with disease and defects, including children who were not alive during the war, and remained in soil for decades and disturbing the food sources.
Agent Orange was the most commonly used chemical during the war to defoliate the forests and farmland of Vietnam and its neighboring countries Laos and Cambodia. This was for many reasons.
One, this took away cover from the Viet Cong, who were guerilla fighters dependent on the cover provided by Vietnam’s thick forests.
The destruction of farmland also caused many of the viet cong to be unable to sustain themselves rurally, which starved them or forced them to move closer to sustain themselves. This would take away rural nourishment support for the Viet Cong during the war, which were their main food sources.
Agent Orange was eventually banned in 1971 by the United States, and remaining stocks were destroyed on a remote island.

Segment 2: The Chemistry Behind Agent Orange

Now we’re going to talk about the chemistry behind Agent Orange, and how it impacted the environment and people involved in the Vietnam War. We will first talk about the composition of Agent Orange, then why this chemical mixture caused so much damage to the environment and people.

Agent Orange is a 1:1 mixture of two herbicides which are (2,4-dichlorophenoxy)acetic acid, or 2,4-D and 2,4,5-Trichlorophenoxyacetic acid, or 2,4,5-T.
The herbicides were originally developed in the 1940s, but only used domestically until after WWII, and came to prominence as chemical warfare weapons in the Vietnam War.
2,4-D, in its pure acid form, is not soluble in water due to its strong solute-solute polar bonds, which cannot be broken by water to form weaker solute-solvent bonds.
Therefore, other forms of the acid, such as in salts or esters, are used instead for water solubility. This can be seen in common forms of the herbicide by itself in use today.
However, 2,4,5-T is almost completely not soluble in water, also due to its strong polar bonds, so Agent Orange was often dissolved in diesel fuel or other organic solvents, which can create stronger solute-solvent bonds with 2,4,5-T than water.
Agent Orange, and its component 2,4,5-T was phased out after the 1970s due to toxicity concerns, however 2,4-D is still used to this day
2,4,5-T and 2,4-D belonged to a class of selective herbicides known as synthetic auxins, which changed growth hormones in broadleaf plants and effectively killed them in high concentrations.
2,4,5-T was phased out because the production of 2,4,5-T would lead to a contaminant byproduct, known as Tetrachloro Dioxin, TCDD, or simply dioxin for the general public.
As you can see in the show notes figure 1, the process of synthesizing 2,4,5-T by heating 2,4,5-Trichlorophenol, which is an organochlorine with the chemical formula C₆H₃Cl₃O, with a base NaOH in CH3OH or water under high pressure will produce 2,4,5-T at 140 degrees celsius. However, a slightly higher temperature of 160 degrees C will cause the production of TCDD.
Figure 1
This is because of the activation energy to start these reactions. The activation energy to start the synthesis of 2,4,5-T is lower than the activation energy to start the synthesis of TCDD, so with extremely controlled temperatures it is possible to synthesize 2,4,5-T without synthesizing dioxin by not giving it enough activation energy.
However, since the difference in temperature is so small and hard to fully control, TCDD was often produced as a side product when synthesizing 2,4,5-T.
Although TCDD was produced in trace amounts, it still caused lots of damage. It’s attributed to as the cause for many forms of cancer encountered in Vietnam veterans, such as Hodgkin’s lymphoma. It’s also believed to be the cause of many birth defects found in children of Vietnam after the war
As previously mentioned, since Agent Orange was sprayed on farmland and lasted for a long time, the contamination of TCDD in food grown from them may be a reason why many people were affected by the toxin.
Agent Orange also had a large impact on the environment, as many countries have condemned its use as a form of “ecocide” because of the damage done to the environment. The US and Vietnamese governments worked together to cleanse the land of Agent Orange, but the recovery of the forests has been hard.

Segment 3: Personal Connections

I wanted to talk about this topic because it’s a commonly overlooked event in history. This can be seen because wars that the U.S. didn’t win, such as the Vietnam war, despite its important impact on the United States, are often overlooked when history is taught to many Americans. In addition, the U.S. committed many war crimes or similar atrocities to other parts of the world, which this episode aimed to shine a light on. I hope you have learned something from this episode, be it history or chemistry. If this episode sparked an interest in you for chemical warfare during the Vietnam War, I highly recommend doing a bit of learning on other rainbow herbicides and napalm as well.

Thank you for listening to this episode of Chemistry Connections. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com.

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