Difference Between Phosphine and Phosgene

The key difference between phosphine and phosgene is that phosphine is an inorganic compound, whereas phosgene is an organic compound.

Both phosphine and phosgene are colorless gases. Although their names sound similar, they are two different compounds.

CONTENTS

1. Overview and Key Difference
2. What is Phosphine 
3. What is Phosgene
4. Side by Side Comparison – Phosphine vs Phosgene in Tabular Form
5. Summary

What is Phosphine?

Phosphine is an inorganic compound having the chemical formula PH₃. It is a colorless and flammable gas having a slightly unpleasant odor. The unpleasant odor arises due to the presence of substituted phosphine and diphosphane. Furthermore, this compound is a toxic gas. And, this gas spontaneously burns in air, producing a luminous flame. Further, it burns, producing phosphoric acid as a dense white cloud.

The molar mass of this compound is 33.99 g/mol. The melting point is −132.8 °C while the boiling point is −87.7 °C. When considering the structure, it is a trigonal pyramidal molecule. The bond angle of H-P-H bonds is 93.5°. Moreover, it has a dipole moment because of the presence of a lone electron pair; the dipole moment of this molecule increases with substitution of methyl groups, while it decreases with the substitution of ammonia.

What is Phosgene?

Phosgene is an organic compound having the chemical formula COCl₂. It is a colorless gas, and it has an odor similar to freshly cut grass. Furthermore, it is insoluble in water but can react with water. It has trigonal planar geometry, and Cl-C-Cl bond angle is 111.8°. Moreover, this compound is a simple acyl chloride that forms from carbonic acid.

In the industrial scale, we produce phosgene via passing pure carbon monoxide and chlorine gas through activated carbon. Here, activated carbon is the catalyst. Further, this reaction is exothermic, and we must cool the reactor during the reaction. When considering the uses of phosgene, we can use it in the production of isocyanates, in the synthesis of carbonates, etc.

What is the Difference Between Phosphine and Phosgene?

Although the names phosphine and phosgene sound similar, they are two different compounds. The key difference between phosphine and phosgene is that phosphine is an inorganic compound, whereas phosgene is an organic compound. Further, phosphine occurs as a colorless, flammable and toxic gas with a slightly unpleasant odor while phosgene occurs as a colorless gas with the odor of freshly cut grass. When considering the structure, the geometry of the phosphine molecule is trigonal pyramidal, while the geometry of phosgene is trigonal planar. Additionally, phosphine is poorly soluble in water, but phosgene is insoluble, and if we add it to water, it can react with water rather than just dissolving there.

Below infographic summarizes the difference between phosphine and phosgene, comparatively.

Summary – Phosphine vs Phosgene

Although the names phosphine and phosgene sound similar, they are two different compounds. Mainly, the key difference between phosphine and phosgene is that the phosphine is an inorganic compound, whereas the phosgene is an organic compound.

Reference:

1. “Phosgene.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.

Image Courtesy:

1. “Phosgene-dimensions-2D” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “Monophosphan” By Phosgene-dimensions-2D.png: Ben MillsSVG-version: n-regen – Phosgene-dimensions-2D.png (Public Domain) via Commons Wikimedia