Phosgene Meaning
Phosgene was incorporated by the Cornish physicist John Davy (1790–1868) in 1812 by uncovering a combination of carbon monoxide and chlorine to daylight.
He named it "phosgene" from the Greek words ‘phos’ (meaning light) and ‘gennaō’ (meaning to give birth) in reference to the utilization of light to advance the reaction.
It slowly got significant in the compound business as the nineteenth century advanced, especially in dye manufacturing/colour fabricating.
This page discusses more on Phosgene, Phosgene Structure, Phosgene Chemical Formula, and Phosgene Uses in detail.
What is Phosgene?
Do you know what Phosgene is? Well! It has a lot many applications in industrial uses. Now, let’s discuss in pointers what Phosgene is.
Phosgene is a colourless, non-flammable gas that has the scent of newly cut hay. It is a manufactured chemical for making pesticides and plastics.
However, limited quantities happen normally starting from the break of chlorinated compounds. Phosgene is utilized in the assembling of different chemicals like dyestuffs, isocyanates, polycarbonates, and corrosive chlorides.
Phosgene can likewise be utilized to isolate minerals. Phosgene is a gas at room temperature, however, is in some cases put away as a fluid under pressure or refrigeration.
Phosgene is a significant mechanical compound used to make plastics, drugs, and pesticides.
At room temperature (70°F), phosgene is a noxious gas.
With cooling and pressure, Phosgene gas can be changed over into a fluid so it tends to be transported and put away. At the point when fluid phosgene is delivered, it rapidly transforms into a gas that remains nearby to the ground and spreads quickly.
Phosgene gas may seem colourless or as a white to the light yellow cloud. At low concentrations, it has a wonderful smell of recently mown roughage or green corn, yet its scent may not be seen by all individuals uncovered. At high concentrations, the odour/scent might be strong and unpleasant.
Phosgene itself is nonflammable (not effectively lighted and consumed).
Phosgene is additionally known by its military assignment, "CG."
Now, we will look at some of the properties of Phosgene:
Point To Note:
Phosgene is an acyl chloride obtained by replacement of the two hydrogens of formaldehyde by chlorine. It is obtained from formaldehyde.
The Below Table Illustrates the Major Properties of Phosgene:
Properties of Phosgene
Other Major Properties of Phosgene Lie Hereunder:
Phosgene shows up as a colourless gas or exceptionally low-bubbling, unpredictable fluid (b.p. 8.3°C, 48°F) with an odour of new-mown feed. It is an incredibly poisonous gas.
Cautioning properties of the gas breathed in are slight, passing may happen inside a day and a half (Lewis, third ed., 1993, p. 1027). Drawn out the openness of the compartments to extreme heat may bring about their brutal cracking and soaring.
The pace of beginning: Immediate and Delayed (Lungs) Persistence: Minutes - hours Odor edge: 0.5 ppm.
Source/use/other peril involves a Dye, pesticide, and different enterprises; history as war gas, destructive/irritating.
Phosgene Chemical Formula
Phosgene is a planar atom as anticipated by the VSEPR hypothesis. The C = O distance is 1.18 Å, the C − Cl distance is 1.74 Å, and the Cl − C− Cl point is 111.8°.
It is one of the most straightforward acyl chlorides, being officially gotten from carbonic corrosive.
The Phosphene gas formula is given as;
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Phosphene Reactions
Phosgene reacts with water to deliver hydrogen chloride and carbon dioxide:
COCl2 + H2O → CO2 + 2 HCl
Similarly, upon contact with alkali, it converts to urea: COCl2 + 4 NH3 → CO(NH2)2 + 2 NH4Cl
Halide reacts with nitrogen trifluoride and aluminium tribromide gives COF2 and COBr2, individually.
Phosgene Uses
Synthesis of Carbonates
Diols react with COCl2 to give either linear or cyclic carbonates (R = H, alkyl, aryl): HOCR2 − X − CR2OH + COCl2 → \[\frac{1}{n}\] [OCR2 − X−CR2OC(O) −]n + 2 HCl
Another example is of phosgene reaction with bisphenol A. to frame Polycarbonates.
Synthesis of Isocyanates
The production of isocyanates from amines outlines the electrophilic character of this reagent and its utilization in presenting the comparable synthon "CO2+.” :
RNH2 + COCl2 → RN = C = O + 2 HCl (R = alkyl, aryl)
Such reactions are led on a laboratory scale in the presence of a base; for example, pyridine neutralizes the hydrogen chloride side-product.
Do You Know?
Phosgene is noxious and was utilized as a compound weapon during World War I, where it was answerable for 85,000 passings.
Notwithstanding its industrial production, limited quantities are formed as a result of the breakdown and the burning of organochlorine compounds.
FAQs on Phosgene
1. What is phosgene and what is its chemical formula?
Phosgene is a highly toxic, colourless gas at room temperature, known for its characteristic odour of newly mown hay or green corn. Its chemical formula is COCl₂, and its IUPAC name is carbonyl dichloride. It is a simple acyl chloride derived from carbonic acid.
2. What are the key physical properties of phosgene?
Phosgene has several distinct physical properties that are important for students to know:
- Molecular Weight: 98.91 g/mol
- Boiling Point: 8.3 °C (meaning it is a gas at standard room temperature)
- Melting Point: −118 °C
- Appearance: Colourless gas which may appear as a white to pale yellow cloud when released as a liquid.
- Solubility: It is insoluble in water (with which it reacts) but soluble in organic solvents like benzene, toluene, and acetic acid.
3. What is the molecular structure and geometry of phosgene (COCl₂)?
According to the VSEPR theory, the phosgene molecule has a trigonal planar geometry. The central carbon atom is double-bonded to an oxygen atom and single-bonded to two chlorine atoms. The key structural parameters are a C=O bond distance of 1.18 Å, a C-Cl bond distance of 1.74 Å, and a Cl-C-Cl bond angle of approximately 111.8°.
4. What are the primary industrial uses of phosgene?
Despite its toxicity, phosgene is a crucial industrial chemical primarily used as a reagent in organic synthesis. Its main applications include the manufacturing of:
- Polycarbonates: A type of durable plastic.
- Isocyanates: Key components in the production of polyurethane foams and resins.
- Pesticides and Herbicides: Used as a building block for various agrochemicals.
- Pharmaceuticals and Dyes: It serves as a precursor in the synthesis of various complex organic compounds.
5. How is phosgene formed from chloroform, and why is this reaction a significant safety concern in a chemistry lab?
Phosgene can be formed when chloroform (CHCl₃) is exposed to air and sunlight. The chloroform undergoes slow oxidation, producing phosgene and hydrogen chloride (HCl). The reaction is: 2CHCl₃ + O₂ → 2COCl₂ + 2HCl. This is a major safety concern because chloroform is a common laboratory solvent. To prevent the formation of this highly poisonous gas, chloroform is always stored in dark-coloured, tightly sealed bottles, filled to the brim to minimise contact with air.
6. Why was phosgene such an effective and dangerous chemical weapon during World War I?
Phosgene's danger as a chemical weapon lies in its insidious nature. Unlike chlorine gas, it has a subtle, non-irritating smell and its severe effects are delayed. Soldiers could be exposed to fatal concentrations without immediate symptoms. The toxic effects, primarily severe pulmonary edema (fluid filling the lungs), would manifest 24 to 48 hours after exposure, leading to suffocation and death. This delayed action made it difficult to treat and caused a high number of casualties.
7. Why is the chemical COCl₂ named 'phosgene'?
The name 'phosgene' was coined by its discoverer, John Davy, in 1812. It originates from the Greek words 'phos' (meaning light) and 'genesis' (meaning birth). This name, which translates to "born of light," was chosen because the chemical was first synthesised by exposing a mixture of carbon monoxide and chlorine to sunlight, where light acted as a catalyst for the reaction.
8. How does phosgene react with water and ammonia?
Phosgene is highly reactive towards nucleophiles. Its reactions with water and ammonia are important examples:
- Reaction with Water (Hydrolysis): Phosgene reacts with water to decompose into carbon dioxide and hydrogen chloride gas. The reaction is: COCl₂ + H₂O → CO₂ + 2HCl.
- Reaction with Ammonia: It reacts with ammonia to form urea, a commercially important compound, and ammonium chloride. The reaction is: COCl₂ + 4NH₃ → CO(NH₂)₂ + 2NH₄Cl.
