chemistry

Phenyldichloroarsine

Phenyldichloroarsine is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Phenyldichloroarsine rather than just read about it. In short: Phenyldichloroarsine, also known by its wartime name phenyl Dick and its NATO abbreviation PD, is an organic arsenical vesicant (blister agent) and vomiting agent developed by Germany and France for use as a chemical warfare agent during World War I. The agent is known by multiple synonyms.

Key takeaways

Phenyldichloroarsine belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Phenyldichloroarsine to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Phenyldichloroarsine from memory before moving on to harder problems.

Reference excerpt

Phenyldichloroarsine, also known by its wartime name phenyl Dick and its NATO abbreviation PD, is an organic arsenical vesicant (blister agent) and vomiting agent developed by Germany and France for use as a chemical warfare agent during World War I. The agent is known by multiple synonyms.

History PD was prepared during 1917–18 in Germany and France, during World War II it was prepared in Germany.

Chemical characteristics

General Phenyldichloroarsine is an odorless, colorless substance that can form hydrochloric acid upon contact with water. The reaction with water is very slow, the substance sinks, and the reaction is considered non-hazardous. Another product of hydrolysis is phenylarsenious acid, which is a severe irritant to the mucous membranes and skin. In an impure state, phenyldichloroarsine may have a slight brown color, in its purest form though there is no color and the substance has an oily texture. An impure solution of PD also emits a characteristically unpleasant horseradish or garlic-like odor, which is detectable at 0.1 ppm. Phenyldichloroarsine is one of four organic arsenicals, the other three are lewisite (L), methyldichloroarsine (MD), and ethyldichloroarsine (ED). PD is considered an analog of lewisite. At its freezing point, -20 °C, PD becomes a microcrystalline solid mass. The compound has a C-metalloid bond between the phenyl group and the arsenic and two covalent bonds between the arsenic and the chlorine.

Synthesis Phenyldichloroarsine is produced by reacting benzene with arsenic trichloride. Anhydrous aluminum chloride acts as a catalyst in this reaction.

Uses Phenyldichloroarsine is an obsolete chemical warfare agent and is classified as a vesicant and a vomiting/incapacitating agent. It was used as a weapon during World War I, where it showed itself as less effective than other vomiting agents. Phenyldichloroarsine is an arsenical vesicant which can be mixed with mustard agents for use in chemical warfare. PD was developed for use in wet environments, because of its tendency to persist in cool and shaded areas. Phenyldichloroarsine can have a persistence lasting anywhere from 2 to 7 days under usual environmental conditions. In open areas, it is more useful as a vomiting agent but in closed-in areas, such as basements, trenches and caves, it is highly effective because of its "extreme" vapor density. Phenyldichloroarsine has also been used by banks and other high-security facilities to defend against security breaches.

Biological effects PD damages the eyes, lungs, throat and nasal membranes. PD immediately affects the eyes and blindness can result, though it requires high doses. It also induces nausea and vomiting, an inhalation of as little as 5-50 milligrams can induce severe vomiting. Long-term exposure to PD can cause systemic damage by replacing calcium with arsenic, extensive bone marrow damage can also result. Due to PD being easily recognized in the field and a relatively fast rate for decontamination procedures to become effective, the chemical is not as useful as other blister agents. The blistering resultant from PD exposure may also be delayed, for as little as 30 minutes, or as long as 32 hours depending upon the concentration of the dose. The molecular toxicology of PD is not well understood, but a 1986 U.S. Army-sponsored report did shed some light on that area. The Army report showed that PD penetrated the red blood cell membrane and interacted with something inside the cell. The study also found that hemoglobin was not responsible for "holding" the PD in its bond with the erythrocytes (red blood cells), instead glutathione was found to be a more likely interacting with PD inside the cell.

Illustrations

Worked examples

Example 1 — a first encounter with Phenyldichloroarsine

Start with the simplest possible case. Write down what Phenyldichloroarsine claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Phenyldichloroarsine before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Phenyldichloroarsine ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Phenyldichloroarsine

In research: Phenyldichloroarsine appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Phenyldichloroarsine in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Phenyldichloroarsine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arsenic(III) compounds, Arsenical vesicants, Organoarsenic chlorides, so understanding it makes those chapters shorter.
In everyday life: Look for Phenyldichloroarsine outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Phenyldichloroarsine in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Phenyldichloroarsine means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Phenyldichloroarsine out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Phenyldichloroarsine in simple terms?

Why does Phenyldichloroarsine matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Phenyldichloroarsine?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Phenyldichloroarsine.