PCl5

Definition

PCl5, or phosphorus pentachloride, is a covalent compound consisting of one phosphorus atom bonded to five chlorine atoms. It is an important chemical species that is relevant in the context of both molecular structure and polarity, as well as the occurrence, preparation, and properties of phosphorus.

5 Must Know Facts For Your Next Test

1. PCl5 is a trigonal bipyramidal molecule, with the phosphorus atom at the center and the five chlorine atoms arranged in a specific geometry.
2. The bond angles in PCl5 are approximately 120 degrees in the equatorial plane and 90 degrees in the axial positions, as predicted by VSEPR theory.
3. Due to the difference in electronegativity between phosphorus and chlorine, the P-Cl bonds in PCl5 are polar, resulting in an overall polar molecule.
4. PCl5 is a Lewis acid, meaning it can accept electron pairs, and is used as a reagent in various organic synthesis reactions.
5. Phosphorus, the central element in PCl5, is a group 15 element that is essential for many biological processes and has a wide range of industrial applications.

Review Questions

• Explain the molecular structure and polarity of PCl5 based on VSEPR theory.
  • According to VSEPR theory, PCl5 has a trigonal bipyramidal molecular geometry, with the phosphorus atom at the center and the five chlorine atoms arranged in a specific pattern. The bond angles in the equatorial plane are approximately 120 degrees, while the axial bond angles are 90 degrees. Due to the difference in electronegativity between phosphorus and chlorine, the P-Cl bonds are polar, resulting in an overall polar molecule. This polarity is an important characteristic of PCl5 that influences its chemical reactivity and behavior.
• Describe the occurrence, preparation, and properties of phosphorus, the central element in PCl5.
  • Phosphorus is a group 15 element that is essential for many biological processes, such as the formation of DNA and ATP. It is widely distributed in the Earth's crust and is commonly found in minerals like apatite. Phosphorus can be prepared by the reduction of phosphate rock with carbon at high temperatures. Elemental phosphorus exists in several allotropic forms, with the most common being white phosphorus, which is highly reactive and flammable. Phosphorus and its compounds, including PCl5, have a wide range of industrial applications, such as in the production of fertilizers, detergents, and incendiary devices.
• Analyze the role of PCl5 as a Lewis acid and its importance in organic synthesis reactions.
  • As a Lewis acid, PCl5 is capable of accepting electron pairs, making it a useful reagent in various organic synthesis reactions. In these reactions, PCl5 can act as an electrophile, facilitating the addition of chlorine atoms or the formation of new carbon-carbon bonds. The polar nature of the P-Cl bonds in PCl5 also contributes to its reactivity, allowing it to interact with nucleophiles and participate in substitution, elimination, and other organic transformations. The versatility of PCl5 as a Lewis acid makes it an important tool in the field of organic chemistry, enabling the synthesis of a wide range of compounds with diverse applications.

Related terms

Covalent Bond:

A chemical bond formed by the sharing of electrons between two atoms, resulting in the creation of a stable, electrically neutral molecule.

Molecular Geometry:

The three-dimensional arrangement of atoms in a molecule, determined by the number of bonds and the principles of valence shell electron pair repulsion (VSEPR) theory.

Electronegativity:

The ability of an atom to attract shared electrons in a chemical bond, which determines the polarity of the bond and the overall polarity of the molecule.