Agent Orange – Part Three – The Synthesis of 2,4,5,-Trichlorophenate

The tactical herbicide Agent Orange, which was used in South-east Asia by the United States Department of Defence during the Vietnam War, was made from equal parts of the nbutyl esters of 2,4,5-T and 2,4,-D. For almost half a century, controversy has surrounded its use, mainly because it contained a highly toxic dioxin impurity (TCDD). Despite this impurity being thoroughly investigated, there is still a lot of confusion by the public regarding how it was formed and why it took so long to be detected. To answer these questions, you have to have a basic understanding of the synthesis of one of the herbicides precursors – once you have that, you soon begin to realise that what you thought you knew about Agent Orange may be wrong.

One of the biggest misconceptions that the general public have is that the dioxin impurity is exclusive to Agent Orange, when in actual fact it was the product of a side reaction during the synthesis of 2,4,5-T’s (the carboxylic acid, not the n-butyl ester) precursor 2,4,5,-Trichlorophenate. This means that any herbicides used during the Vietnam war that contained a derivative of 2,4,5-T will have contained a small, but substantial, quantity of this harmful impurity. Agents Green, Pink, and Purple, of which a combined total of 3 million litres was sprayed on Vietnam between 1961-1972, all contained 2,4,5-T derivatives and, therefore, all contained the dioxin impurity. 2,4,5-T was also used in domestic herbicides which too would have had contained trace amounts of TCDD. 

One of the first warning signs that the precursor 2,4,5,-Trichlorophenate was generating toxic by-products during its synthesis occurred in 1949 at a Monsanto chemical plant in Nitro, West Virginia. There, workers were synthesising a compound called 2,4,5-trichlorophenol (TCP) in a two-step process via the same 2,4,5,-Trichlorophenate intermediate as 2,4,5,-T.

This intermediate can be synthesised by the hydrolysis of a compound called 1,2,4,5-tetrachlorobenzene (TCB) in ethylene glycol using sodium hydroxide at 170-180C. The process in Nitro, however, was slightly different and methanol was used instead of ethylene glycol as a solvent, which had one major drawback; it had to be used under a fairly high pressure of 20 atmospheres.

The reaction formed small quantities of the impurity (about 1ppm) by the elimination of two molecules of HCl from two 2,4,5,-Trichlorophenates. However, if the temperature was raised this could increase a thousand fold, but the majority of the impurity was removed by the distillation purification process which gave a maximum concentration of 10ppb.

On March 8, 1949 a runaway reaction was taking place in an autoclave (a pressurised reaction vessel) used to synthesise 2,4,5,-Trichlorophenate at Monsanto chemical plant. The uncontrolled reaction increased the temperature and pressure within the vessel synthesising large amounts of the dioxin impurity whilst simultaneously exceeding the safety limits of the reactor. The increase in pressure caused a pipe to rupture, spraying a black powder and a thick, sticky, dark brown substance inside the building before eventually the safety bursting disk gave way, allowing the pressurised content to vent through a chimney.

Within an hour, workers were back in the building to assess the damage and to clean up. Few safety precautions were taken by those entering the building, who were unaware of the dioxin impurity present in the pre-purified reaction mixture which now coated the inside of the building. Soon after, the workers involved began to complain of health problems and started suffering from chloracne which is an acne-like eruption of blackheads, cysts, and pustules.

Chloracne is associated with overexposure to certain halogenated aromatic compounds known as chloracnegens, but is particularly linked with TCDD – so much so that it is considered a sign of exposure to this compound. For example, when the Ukrainian politician, Viktor Yushchenko, was poisoned in 2004, the doctors were able to deduce that it was TCDD after he developed chloracne, which left him disfigured.

At this point, you should be asking the same question I did when I discovered this classic symptom of TCDD exposure. If this impurity causes chloracne, then why do so few who claim their ill health is a result of exposure to Agent Orange suffer from it? Don’t get me wrong, I am not saying that TCDD has no negative effects; nor am I downplaying these people’s suffering, I am simply pointing out that this established symptom of dioxin exposure is not seen in the majority of people who think the herbicide has caused them harm.

Believe me when I say that we have barely scratched the surface, and in the following blog posts I plan to discuss other industrial accidents and the long time health effects of those exposed to large quantities of TCDD and how they compare to those exposed to Agent Orange. I also plan to explain why the impurity took so long to identify, but for now I leave you with a quote by Arthur Conan Doyle.

“There is nothing more deceptive than an obvious fact.”

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About Myles Power (662 Articles)
My name is Myles Power, and I run the educational YouTube channel, powerm1985. I spend what little free time I have sharing my love of SCIENCE! through home experiments, visiting sites of scientific interest, and angrily ranting at pseudoscience proponents. I am also one of the founding members of the podcast 'The League of Nerds' - which I co-host with James from 'The History of Infection'.

2 Comments on Agent Orange – Part Three – The Synthesis of 2,4,5,-Trichlorophenate

  1. Detailing the runaway reaction in the autoclave at Monsanto was a fascinating read and I very much look forward to hearing about other chemical factory accidents.

    Liked by 1 person

  2. You base your assumptions on the idea that all those exposed were in direct contact with major amounts Agent Orange, Pink, Green, etc.
    A mistake many seem to make when repeating what was written by the hand-picked scientists working for those who had a vested interest in downplaying the severity of the problem experienced by those contaminated.
    In truth, many people who are now suffering were exposed to long-term, smaller amounts of these chemical cocktails, which allowed their bodies to adjust differently than those in direct “heavy contact”. It began a very long process of cellular replication one infinitesimal cell at a time, over years, until now, decades later, when they need help the most due to the overburdening of their systems by this dioxin, they are ignored and refused help from the very people who know best how to treat them. People spouting rhetoric such as yours has doomed millions of men and women to a slow miserable demise because you read, but you do not do your own investigations and study. You are a parrot for chemical companies and governments who desire not to suffer the financial losses they deserve to suffer, while those suffering the effects from their blunders are simply trying to get help in order to live another year.
    It is thinking, like that which you have displayed, that is causing men and women who were exposed in Asia to long-term light contamination to suffer, at the hands of those who should be offering help, but do not, because of foolish comments like the one you shared.
    Anyone can copy/paste from others. A real journalist would take the time to learn and understand.
    I am one of those who is denied proper diagnostic help because I do not exhibit any of the signs decided upon by the chemical companies who sold the military strength defoliants used in Asia to a government, based on the criteria you’ve mentioned. I am one of a couple of million who were assigned duty on installations in Thailand where perimeters were sprayed constantly with defoliants up to 50 times stronger and more potent than any you mentioned being used in normal agricultural settings. We’ll lose another few thousand this week too, because of jibberish like you’ve copied and pasted.
    Why don’t any of you people ever crack open a chemistry book, and learn for yourselves?
    50 times stronger than what you think it was, and sprayed relentlessly over and over each month for 10 years around a small installation. Over a thousand feet of contaminated earth reaching out, all the way around the installations, uncovered and open to the elements, being driven inward by winds of up to and over 100 MPH, and carried along with rain runoff and debris from all over. All of it contaminated and deadly. Left in the sun to bake and turn to dust, it became airborne and drifted into every centimeter of the installations, just as deadly as the day it was sprayed.
    Tracked all over the bases, on every single boot of those who worked on the perimeter, for over ten long years.
    Carried along the roads throughout the installations on all vehicle tires spattering deadly mud everywhere they went.
    Brought in to the working, living, eating, bathing, and sleeping areas, of all the people living and working on those installations.
    Contaminated dust, mud, water, boots, tires, and more, all as deadly as the day it was applied, and all finding a way into the lives and bodies of unsuspecting men and women on military installations throughout Thailand, Laos, Cambodia, and elsewhere, in addition to Vietnam.
    Unlike an immunity to arsenic which can be built up over a period of time, this dioxin had/has no tolerance allows an infected individual escape. It only has the one program. Destroy the immune system of the host.

    Like

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