Chemical Warfare Agents: Types, Properties, and Chemical Principles

Chemical Warfare Agents

Overview of Chemical Warfare Agents

Chemical warfare agents are toxic chemicals designed for use in military operations to harm, incapacitate, or kill. They are classified based on their physiological effects and chemical properties. Understanding their chemistry is essential for recognizing their mechanisms and potential countermeasures.

• Choking agents: Attack lung tissue, causing pulmonary edema (e.g., chlorine, phosgene).

• Blood agents: Inhibit enzymes involved in cellular respiration, similar to carbon monoxide poisoning (e.g., cyanide, cyanogen).

• Blister agents (vesicants): Cause severe blistering and tissue damage (e.g., mustards, lewisite).

• Nerve agents: Disrupt nervous system function, highly toxic and lethal (e.g., sarin, VX, Novichok).

• Incapacitants: Cause temporary physiological or psychological effects (e.g., tear gas, BZ, Kolokol-1).

• Incendiaries: Designed to start fires or destroy equipment (e.g., napalm, thermite, white phosphorus).

Nerve Agents

Novichok Agents

Novichok agents are a class of nerve agents developed in the Soviet Union and Russia. They are considered among the most toxic chemical warfare agents known, with some variants being several times more lethal than VX. Their chemical structures are not fully disclosed, but they are believed to be organophosphorus compounds designed as binary agents (components mixed just before use).

• History: Developed from 1971 to 1993 under the FOLIANT program.

• Notable incidents: Suspected use in the poisoning of Sergei and Yulia Skripal (2018) and Alexei Navalny (2020).

• Properties: Extremely stable, persistent in the environment, and highly lethal.

• Examples: A-230, A-232, A-234 (A-series agents).

Chemical Principle: Novichok agents inhibit acetylcholinesterase, leading to accumulation of acetylcholine and continuous nerve signal transmission, resulting in muscle paralysis and death.

Incapacitants

Physical Incapacitants: Tear Agents

Physical incapacitants are chemicals that cause temporary irritation to the eyes, skin, and respiratory tract. They are commonly used for riot control and crowd management. The most widely used tear agents are CN, CS, and CR.

• CN (Chloroacetophenone): Known as "mace" or "tear gas," highly toxic by inhalation and ingestion, rapid onset (20–60 s), effects last minutes.

• CS (O-Chlorobenzylidene malononitrile): Developed in the 1950s, replaced CN, rapid onset, effects last 5–20 minutes, used in riot control and training.

• CR (Dibenzoxazepine): More irritating than CS, less toxic, effects can last up to 6 hours for the eyes.

Mechanism: These agents stimulate sensory nerves, causing pain, tearing, and respiratory distress.

Comparison of Riot Control Agents

Property	CN	CR	CS
Appearance	Colourless crystalline solid	Yellow needles	White crystalline solid
Chemical Name	2-Chloroacetophenone	Dibenz(b,f)-1,4-oxazepine	2-Chlorobenzalmalononitrile
Chemical Formula	C8H7ClO	C13H9NO	C10H5ClN2
Boiling Point (°C)	244–245	335	310–315
Solubility in Water	Practically insoluble	Practically insoluble	Practically insoluble
Volatility (mg/m3)	110 (20°C)	0.63 (25°C)	0.35 (20°C)

Physical Incapacitants: Vomiting Agents

Vomiting agents cause severe irritation of the respiratory tract, leading to sneezing, coughing, nausea, and vomiting. They are used for short-term incapacitation.

• Examples: Adamsite (DA), Diphenylchlorarsine (DA), Diphenylcyanoarsine (DC).

• Onset: Effects appear within minutes and subside in 1–2 hours.

Physical Incapacitants: Capsaicin (Pepper Spray)

Capsaicin is the active component in pepper sprays, derived from capsicum plants. It activates sensory neuron receptors, causing intense irritation and inflammation of the airway mucosa.

• Commercial use: Pepper sprays contain 1–15% capsaicinoids.

• Scoville Heat Units (SHU): Measure the pungency of capsaicinoids.

Psychoincapacitants

Psychoincapacitants are chemicals that alter the central nervous system, causing hallucinations, confusion, or sedation. They are effective at low doses and do not cause permanent injury at proper concentrations.

• CNS depressants: Antipsychotics, opioid-like agents (e.g., Kolokol-1).

• CNS stimulants: Amphetamines, cocaine.

• Psychedelics: LSD (lysergic acid diethylamide).

• Deliriants: Agent 15, BZ (3-Quinuclidinyl benzilate).

Agent BZ: Causes hallucinations, involuntary muscle movements, and psychotropic effects. Full recovery occurs after 3–4 days.

Incendiary Agents

Thermite

Thermite is a mixture of metal powder (usually aluminum) and a metal oxide (commonly iron(III) oxide). When ignited, it undergoes an exothermic reaction, producing extremely high temperatures (up to 2400°C). It is used in incendiary devices and for welding metals.

• Reaction: $\mathrm{Fe_2O_3 + 2Al \rightarrow 2Fe + Al_2O_3}$

• Applications: Hand grenades, bombs, exothermic welding (e.g., railway rails).

Napalm

Napalm is a gel-like incendiary composed of a gelling agent (aluminum salts of naphthenic and palmitic acids) and a volatile fuel (petrol or diesel). Napalm B contains polystyrene, benzene, and gasoline. It burns at 800–1200°C and is used in flamethrowers and bombs.

• Historical use: Developed in 1942, widely used in World War II and Vietnam.

White Phosphorus (WP)

White phosphorus is an allotrope of phosphorus used as an incendiary and smoke-producing agent. It ignites spontaneously in air, producing dense white smoke and causing severe thermal and chemical burns.

• Applications: Smoke grenades, munitions, and battlefield obscurants.

• Hazards: Causes nausea, diarrhea, and cardiac arrhythmia upon exposure.

Summary Table: Types of Chemical Warfare Agents

Type	Mode of Action	Examples
Choking agents	Attack lung tissue, cause pulmonary edema	Chlorine, phosgene
Blood agents	Inhibit cellular respiration enzymes	Cyanide, cyanogen
Blister agents	Cause severe blistering and tissue damage	Mustards, lewisite
Nerve agents	Disrupt nervous system function	Sarin, VX, Novichok
Incapacitants	Temporary physiological/psychological effects	CN, CS, CR, BZ, Kolokol-1
Incendiaries	Start fires, destroy equipment	Thermite, napalm, white phosphorus