phosgene

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Carbonyl chloride

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synonym COCl2 (COCl2) generally refers to phosgene (carbonyl chloride)

This entry is made by China Science and Technology Information Magazine Participate in editing and review Science Popularization China · Science Encyclopedia authentication.

Phosgene, also known as carbonyl chloride, chemical formula: COCl two , an important organic intermediate, is a very active electrophilic reagent, easy to hydrolyze, and is a severely asphyxiating toxic gas, It is highly toxic^[1] Inhalation of high concentration may cause pulmonary edema.

Chinese name: phosgene
Foreign name: Phosgene
Alias: Carbonyl chloride
chemical formula: COCl two
molecular weight: ninety-eight point nine one six
CAS login number: 75-44-5
EINECS login number: 200-870-3
Melting point: -118 ℃
Boiling point: 8.2 ℃

Water solubility: Slightly soluble
Density: 4.298 kg/m³
Appearance: Colourless gas
Flash point: -29.57 ℃
Application: Used for organic synthesis, manufacturing dyes, rubber, pesticides, plastics, etc
Security description: S9；S26；S28；S36/37/39；S45；S62
Hazard symbol: T+；F
Hazard description: R11；R26；R34；R48/20；R63；R65；R67

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Physical and chemical properties

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Density: 4.298kg/m three

Melting point: - 118 ℃

Boiling point: 8.2 ℃

Flash point: - 29.57 ℃

Refractive index: 1.419

Saturated vapor pressure: 161.6kPa (20 ℃)

Critical temperature: 182 ℃

Critical pressure: 5.67MPa

Appearance: colorless gas

Solubility: slightly soluble in water, soluble in most organic solvents such as aromatics, benzene, carbon tetrachloride, chloroform, acetic acid, etc

Molecular structure data

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Molar refractive index: 16.4

Molar volume (cm three /mol）：64.9

Isotonic specific volume (90.2K): 153.8

Surface tension (dyne/cm): 31.5

Polarization (10 -24 cm three ）：6.5

Calculate chemical data

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Reference value for drainage parameter calculation (XlogP): 1.8

Number of hydrogen bond donors: 0

Number of hydrogen bond receptors: 1

Number of rotatable chemical bonds: 0

Number of tautomers: 0

Topological molecular polar surface area: 17.1

Number of heavy atoms: 4

Surface charge: 0

Complexity: 29

Number of isotope atoms: 0

Determine the number of atomic structure centers: 0

Number of uncertain atomic structure centers: 0

Determine the number of chemical bond structure centers: 0

Number of uncertain chemical bond structure centers: 0

Number of covalent bond units: 1

Preparation

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The production principle of phosgene When it is made in the laboratory, carbon tetrachloride can react with fuming sulfuric acid. Heat carbon tetrachloride to 55-60 ℃, drop in fuming sulfuric acid, and phosgene will escape. If liquid phosgene is required, condense the phosgene.

Reaction equation: SO three +CCl four → SO two Cl two +COCl two ↑

The reaction mechanism is shown in the right figure:

Phosgene is usually obtained by the reaction of carbon monoxide and chlorine in industry. This is a strongly exothermic reaction. The synthesizer with activated carbon should have a water cooling jacket, and the reaction temperature should be controlled at about 200 ℃. In order to obtain high-quality phosgene and reduce equipment corrosion, thoroughly dried carbon monoxide should be kept in an appropriate excess when mixed with chlorine. The mixed gas is introduced from the upper part of the synthesizer, passes through the activated carbon layer, and is quickly converted into phosgene. When the synthesizer with specification of Ф 700 × 2900 is selected, each set can produce phosgene 200t per year.

Raw material consumption quota: chlorine (>99%) 925kg/t; Oxygen (under standard conditions) 268 (m) kg/t; Coke 400kg/t.

Direct reaction of chloroform and hydrogen peroxide:

CHCl three +H two O two =HCl+H two O+COCl two (Phosgene) -- Chloroform is easily oxidized to produce phosgene if it is not properly stored.

Oxygen can also be produced from hydrogen peroxide and reacted with chloroform:

2CHCl three +O two =2HCl+2COCl two Phosgene

Phosgene leakage is absorbed by water mist, and phosgene is easily hydrolyzed:

COCl two +H two O=2HCl+CO two

Chlorine can also react with carbon monoxide

Cl two +CO==Light==Activated carbon or Pt==COCl two (See photo reaction)

toxicity

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summary

This product is a typical temporary poison. Semi lethal dose LD of inhalation poisoning fifty 3200mg/kg, half disabling dose 1600mg · min/m three 。 After inhalation, symptoms will appear after several hours of incubation period, such as dyspnea, chest tenderness, blood pressure drop, coma and even death in severe cases. The gas mask can effectively protect, and usually does not need to be sterilized. Antipoisons include urotropine, etc. Artificial respiration is prohibited for those with pulmonary edema.

Health hazards

Invasion route: inhalation and percutaneous absorption.

Health hazard: it mainly damages the respiratory tract, leading to chemical bronchitis, pneumonia, and pulmonary edema.

Acute poisoning: mild poisoning, patients with tears, photophobia, pharyngeal discomfort, cough, chest tightness, etc; Moderate poisoning, except for the aggravation of the above symptoms, the patient has mild dyspnea and mild cyanosis; Severe poisoning may cause pulmonary edema or adult respiratory distress syndrome. The patient may cough violently, cough a lot of foam sputum, respiratory distress, and obvious cyanosis. There is a period of symptom remission (generally 1-24 hours) before the occurrence of pulmonary edema. It can be complicated with mediastinal and subcutaneous emphysema.

Toxicology and environment

Acute toxicity: LC fifty 1400mg/m three , 1/2 hour (inhaled by rats); 3200mg/m for human inhalation three , death; Inhalation of 25ppm × 30min is the minimum lethal concentration.

Subacute and chronic toxicity: animals inhaled 0.0008mg/L for 5 hours (5 days), 40% of which developed emphysema.

Pollution source: Phosgene is used as polyurethane product treatment agent, plasticizer, polycarbonate raw material, fiber treatment agent, herbicide, explosive stabilizer, dyes, dye intermediates and drug raw materials, and it is also used in production to escape, emit, drip, leak or accidentally leak.

Hazard characteristics: non combustible. The chemical reaction activity is high, and it is highly corrosive when encountering water.

Combustion (decomposition) product: hydrogen chloride.

Environmental standard: National Occupational Health Standard of the People's Republic of China GBZ2.1-2007 Occupational exposure limit for hazardous factors in the workplace Chemical hazardous factors Maximum allowable concentration of hazardous substances in the air of workshops MAC: 0.5mg/m three 。

Poisoning mechanism

The main pathological changes after phosgene inhalation poisoning are Toxic pulmonary edema 。 Pulmonary edema is Pulmonary capillaries The result of increased permeability. There are many theories about the causes of pulmonary edema, such as acylation, direct action, hydrochloric acid action Neuroreflex The effects, pulmonary hemodynamic changes, etc., have their own experimental basis. However, neither hypothesis can fully explain the occurrence and development of pulmonary edema

It is generally believed that the enhanced permeability of pulmonary capillary wall is closely related to the acylation of phosgene. Phosgene is an acyl halide compound, and the active group is carbonyl (O=C), which is very active in chemical property amino 、 Mercapto group 、 hydroxyl And other important functional groups Acylation reaction It causes extensive inhibition of the lung enzyme system, thus affecting the normal metabolism and function of cells, damaging the lung gas blood barrier, increasing the permeability of pulmonary capillaries, and causing pulmonary edema. In addition, Phosgene poisoning When, Pulmonary surfactant Damage is also one of the important factors. Normally, the alveolar surface is covered with a layer of surfactant secreted by alveolar type II epithelial cells, which can reduce the surface tension of the fluid in the alveoli, prevent the alveoli from collapsing when expiring, and keep the alveoli dry. Dipalmitoyl phosphatidyl choline (DPPC) is pulmonary surfactant One of the main components of. In its biosynthesis The involvement of acyl coenzyme A ester acyltransferase is required. After phosgene poisoning, the activity of this enzyme decreases, so the content of DPPC in the alveolar wall decreases, so that the function of pulmonary surfactant decreases, so that the surface tension of the liquid in the alveoli increases, causing the collapse of the alveoli, and the alveolar pressure decreases significantly. The hydrostatic pressure of the pulmonary capillaries against it increases, and a large amount of fluid is extravasated from the blood vessels, leading to pulmonary edema.

pathological change

The pathophysiological changes of phosgene and diphosgene poisoning are mainly caused by pulmonary edema.

In case of inhalation poisoning, the breathing becomes slow for a short time, followed by shallow and fast breathing. After the occurrence of early pulmonary edema, due to the reduction of alveolar respiratory surface area and the thickening of alveolar walls, the gas exchange in the alveoli was affected. With edema liquid filling the respiratory tract, Bronchospasm Bronchial stenosis caused by swelling of its mucous membrane, resulting in pulmonary ventilation obstruction, resulting in respiratory blood hypoxia, leading to a decrease in blood oxygen content, CO two The content increases, and the skin and mucosa are cyan. At this time, the respiratory and circulatory functions have compensatory changes, such as rapid breathing, increased intercostal muscle activity, fast and powerful heartbeat, and slightly elevated blood pressure.

In the late stage of pulmonary edema, because ① there is a lot of fluid in the alveoli, the pressure in the lungs increases, which increases the load of the right heart; ② A large amount of plasma infiltrates into the lungs, reducing the blood volume in the blood circulation, and increasing the blood concentration and viscosity. The increase of peripheral resistance aggravates the load of left heart; ③ Long term severe blood hypoxia Muscular dystrophy Therefore, the cardiac contractility may be weakened Arrhythmia , slow circulation, gradually lower blood pressure and other manifestations of heart failure. The latter can aggravate tissue hypoxia, increase the production of incomplete oxidation in the body, and lead to acidosis and Electrolyte disorder 。 Blood CO two The content gradually decreases, and the viscera Telangiectasia The peripheral capillaries contract, the skin mucosa turns pale, the blood pressure drops sharply, acute circulatory failure occurs, and shock occurs. At this stage, due to pulmonary edema and circulatory failure, the body lost its ability to compensate.

With the development of pulmonary edema, a large amount of plasma is extravasated from pulmonary capillaries, resulting in a decrease in plasma volume, blood concentration, a decrease in plasma protein, an increase in the number of red and white blood cells, hemoglobin, and an increase in hematocrit. These changes were consistent with the degree of pulmonary edema. Due to the sticky blood, slow blood flow, and tissue destruction, the blood coagulation increases. Thus, thrombosis and embolism can be formed.

The central nervous system is very sensitive to hypoxia. At the initial stage of hypoxia, the cerebral cortex is excited, with restlessness, headache, dizziness, etc; When the hypoxia is serious, it gradually turns to inhibition, indifference, fatigue, etc. The hypoxia further develops, the inhibition of cerebral cortex deepens, and spreads to the subcortical area. The respiratory and circulatory center can be turned from excitement to inhibition, and the respiratory and heartbeat can be weakened, leading to central paralysis, resulting in respiratory and heartbeat stops and death.

Pathological anatomy showed that the skin was pale, the thorax was enlarged, the intercostal space disappeared, and pink foamy secretions were discharged from the mouth and nose, and more were discharged when the chest was squeezed. The lung presents "marble like" due to various diffuse pathological changes such as pulmonary edema, emphysema, pulmonary congestion, atelectasis and mild hemorrhage.

clinical manifestation

Phosgene participation activation method

Phosgene poisoning can be clinically divided into four types according to the degree of poisoning: mild, moderate, severe and lightning. Mild poisoning, mild symptoms, no obvious stage, only dyspepsia and bronchitis symptoms, can recover within a week. Lightning poisoning is extremely rare. It usually occurs when the concentration of inhaled toxic agent is very high. Within a few minutes after poisoning, people may die due to reflex respiration and cardiac arrest.

Phosgene can be used for preparation and activation polyethylene glycol , used to modify protein drugs and increase the stability of protein drugs.

Toxicological data

Toxicity test data reported in literature and journals
number	Toxicity type	test method	Test object	Dosage	Toxic effect
one	acute toxicity	inhalation	human beings	50 ppm/5M	No values other than lethal dose were reported for detailed effects
two	acute toxicity	inhalation	Adult male	360 mg/m three /30M	No values other than lethal dose were reported for detailed effects
three	acute toxicity	inhalation	human beings	25 ppm/30M	Lung, chest or respiratory toxicity - other changes
four	acute toxicity	inhalation	cat	190 mg/m three /15M	No values other than lethal dose were reported for detailed effects
five	acute toxicity	inhalation	mammal	50 ppm/5M	No values other than lethal dose were reported for detailed effects
six	acute toxicity	inhalation	mammal	11 mg/m three /30M	No values other than lethal dose were reported for detailed effects
seven	Chronic toxicity	inhalation	Rat	200 ppb/6H/4W-I	1. Lung, chest or respiratory toxicity - changes in structure and function of trachea and bronchus 2. Lung, chest or respiratory toxicity - changes in lung weight
eight	Chronic toxicity	inhalation	Rat	250 ppb/4H/17D-I	1. Lung, chest or respiratory toxicity - other changes 2. Lung, chest or respiratory toxicity - changes in lung weight 3. Biochemical toxicity - inhibition or dehydrogenase induction
nine	Chronic toxicity	inhalation	Rat	500 ppb/6H/12W-I	1. Lung, chest or respiratory toxicity - changes in structure and function of trachea and bronchus 2. Lung, chest or respiratory toxicity - changes in lung weight 3. Nutrition and metabolic system toxicity - weight loss or weight gain rate decrease

Emergency Management

Evacuate the personnel in the leakage contaminated area to the windward place quickly and isolate them immediately. Isolate 150 meters in case of small leakage and 450 meters in case of large leakage, and strictly restrict access. It is recommended that emergency personnel wear self-contained positive pressure respirators and anti poison clothing. Enter the site from the upwind. Cut off the leakage source as much as possible. Reasonable ventilation to accelerate diffusion. Spray ammonia or other dilute lye for neutralization. Build a dike or dig a pit to collect a large amount of wastewater generated. Leaking containers shall be properly treated, repaired and inspected before reuse.

Phosgene is easily hydrolyzed, even in cold water, the hydrolysis rate of phosgene is also very fast. Water source, water containing food and water absorbing substances will not be poisoned. Phosgene reacts quickly with ammonia, mainly producing non-toxic substances such as urea and ammonium chloride. Therefore, concentrated ammonia can sterilize phosgene. Phosgene reacts with organic amine to form diphenylurea white precipitate and aniline hydrochloride. Phosgene can be tested by this reaction. Phosgene is quickly decomposed in alkaline solution to form non-toxic substances. All kinds of alkali and alkaline substances can sterilize phosgene.

Protective measures

Respiratory system protection: filter type gas mask (full face mask) should be worn during normal operation. In case of emergency rescue or evacuation, it is recommended to wear an air respirator. Eye protection: protection has been made in respiratory system protection.

Body protection: wear adhesive tape anti-virus clothing.

Hand protection: wear rubber gloves.

Others: Smoking, eating and drinking are prohibited at the work site. Pre employment and regular physical examination shall be carried out.

First aid measures

Skin contact: Take off the contaminated clothes and wash with flowing water.

Eye contact: Lift the eyelid and flush with flowing water or physiological saline. Get medical attention.

Inhalation: quickly leave the site to a place with fresh air. Keep the respiratory tract unobstructed. If breathing is difficult, give oxygen. If breathing stops, perform artificial respiration immediately. Get medical attention.

Fire extinguishing method: This product is nonflammable. Firefighters must wear filter type gas masks (full face masks) or isolated respirators, wear full body fire and gas protective clothing, and extinguish the fire at the windward place. Cut off the air supply. Spray water to cool the container, and move the container from the fire site to an open place if possible. In case of phosgene leakage, a small amount of phosgene can be dispersed with steam, and a large amount of phosgene can be flushed with liquid ammonia spray.

Extinguishing agent: spray water, dry powder, carbon dioxide.

Poisoning stage

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The condition of moderate and severe poisoning develops rapidly and seriously. The typical clinical manifestations can be divided into four stages:

Stimulation period

Inhalation of phosgene causes immediate irritation symptoms, which mainly include: eye and respiratory tract irritation symptoms appear early, eye pain, tears, cough, chest tightness and suffocation, respiratory rate change, abnormal smell or persistent light smell, throat and Retrosternal pain Etc; The symptoms of autonomic nerve and central nervous system include headache, dizziness, fatigue, restlessness or few words, indifference, nausea, vomiting, upper abdominal pain, etc. When phosgene inhalation dose is equal, high concentration of phosgene is poisoned for a short time, and the irritation symptoms are serious; The symptoms of long-term poisoning with low concentration are mild. However, when the inhalation dose is large, the respiratory tract irritation symptoms are obvious and the duration is longer.

incubation period

The irritation symptoms disappeared or alleviated, and the conscious symptoms improved, but the pathological process was still developing, and pulmonary edema was gradually forming. The incubation period is generally 2-13 hours. Severe poisoning: 2-4 hours, even 1 hour; Moderate poisoning lasts 8-12 hours, sometimes up to 24 hours.

Pulmonary edema stage

It may occur suddenly or slowly from the incubation period to the pulmonary edema period, which is generally 1-3 days.

The early symptoms of pulmonary edema (interstitial pulmonary edema first) include: general fatigue, headache, chest tightness, shallow and fast breathing, increased pulse, cough, restlessness, etc. On auscultation, the breath sounds are weakened, and there are fine moist rales or twirling sounds at the bottom of the lung. Chest imaging showed signs of pulmonary edema. Then, the general condition worsened and soon appeared Alveolar pulmonary edema 。 Typical symptoms and signs are asthma, dyspnea, frequent coughing, coughing up a lot of pink foam sputum, rapid pulse, nausea, vomiting and Upper abdominal pain Etc. Drumming and dullness can be heard on percussion of chest. The lower boundary of lung decreased, and the boundary of heart dullness disappeared; The whole lung was covered with dry and wet rales during auscultation. The blood test showed signs of blood concentration, Arterial partial pressure of oxygen 、 Blood oxygen saturation Lower. Alveolar pulmonary edema progresses rapidly, and generally reaches its peak within 24 hours. The pulmonary edema stage can be divided into two stages depending on whether the circulatory system functions well.

1. Cyanotic hypoxia stage: in this stage, the blood oxygen content decreases, and the skin and mucosa are cyanotic, but the circulatory function can still compensate. The blood pressure is normal or slightly high, and the pulse is fast and powerful. Consciousness is clear, and the temperature can rise up to 38~39 ℃. CO due to pulmonary edema two Obstruction of excretion, increased carbonic acid in blood, resulting in Respiratory acidosis ； CO can also be caused by excessive ventilation two Excessive discharge, resulting in Respiratory alkalosis 。

2. Pale (or shock) hypoxia stage: the condition continues to deteriorate, and breathing is extremely difficult. In severe cases, all the auxiliary respiratory muscles participate in exercise, and gradually appear circulatory failure: irregular pulse count, decreased blood pressure, pale skin and mucosa, cold sweat, and gradually fall into coma. At this time, the blood oxygen content is lower, and the products of incomplete oxidation are increased, leading to metabolic acidosis.

The symptoms and signs of phosgene poisoning reach the peak within 24 to 48 hours. If not treated in time, they may die within 1 to 3 days, and severe poisoning may die within 5 days. Therefore, those who inhale phosgene should be closely observed for at least 3-4 days.

convalescence

The pulmonary edema fluid can be absorbed within 2-4 days after the onset of the disease after mild poisoning or treatment, and the general condition is improved. Cough, shortness of breath, decreased sputum, decreased body temperature, and lung rales decreased or disappeared. X-ray examination, pulmonary function and blood gas analysis results gradually returned to normal. Generally, the patient is basically recovered in 5-7 days after poisoning, and can recover in 2-3 weeks. However, dizziness, dry throat, anorexia, and unstable respiratory and circulatory functions still occurred within a few weeks.

if there be Secondary infection The disease usually worsens 3 to 4 days after poisoning. The body temperature continues to rise, and the absorption of pulmonary edema is slow, which can be caused by Bronchopneumonia And death. In addition, other complications may occur, such as pleurisy, bronchitis, occasionally pulmonary embolism, pulmonary gangrene, pulmonary abscess, and embolism in lower limbs, brain, heart, and retina.

sequela

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It mainly includes chronic bronchitis, emphysema bronchiectasia , advanced lung abscess, tuberculosis constitution, etc. The prognosis of phosgene poisoning depends on the inhalation dose, condition, treatment and complications. It is difficult to judge the prognosis during the incubation period. The patients with pale asphyxia have poor prognosis. The time of death is mostly within 1~2 days after poisoning. Those who can spend more than 48 hours can generally recover with sequelae. The main causes of death were severe hypoxia and circulatory failure caused by pulmonary edema. Most patients died of bronchopneumonia in late stage.

Phosgene poison

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Phosgene is toxic Chemical warfare agent For manufacturing Poison gas bomb 。 Phosgene was first used in World War I.

Since the Ypres Poison Gas War, decision-makers and commanders on both sides of the war have become enthusiastic about chemical warfare. The war promoted chemical weapon With the development of the World War I, a variety of poisons appeared. In addition to chlorine, phosgene also appeared, which is a battlefield poison that destroys lives.

Phosgene is a colorless gas synthesized by carbon monoxide and chlorine under sunlight. It can damage human respiratory organs and even cause death in serious cases. On December 19, 1915, the German army launched rockets filled with phosgene. More than 1000 people were poisoned and more than 100 died on British positions.

In World War I, phosgene was widely used. Both belligerents used phosgene, with a consumption of 100000 tons.

During World War II, the Japanese army Mustard gas It is too toxic to protect itself. So they aimed at phosgene. Because phosgene can only be poisoned through the respiratory tract, and our army has no protection, we used phosgene in large quantities, and called it "special smoke" (the Japanese army's implicit name for suffocating toxic gas).

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