The key difference between inorganic phosphate (Pi) and pyrophosphate (PPi) is that inorganic phosphate compounds can be found as a phosphate group attached to metal cation(s) whereas pyrophosphates can be found as two phosphate groups linked to each other through a P-O-P linkage and this anion is associated with metal cation(s).
Phosphates are inorganic compounds. There are different types of phosphates, including diphosphates, orthophosphates, pyrophosphates, etc.
CONTENTS
1. Overview and Key Difference
2. What is Inorganic Phosphate (Pi)
3. What is Pyrophosphate (PPi)
4. Inorganic Phosphate (Pi) vs Pyrophosphate (PPi) in Tabular Form
5. Summary – Inorganic Phosphate (Pi) vs Pyrophosphate (PPi)
What is Inorganic Phosphate (Pi)?
Inorganic phosphates are salts of phosphoric acid. In these compounds, we can see a phosphate group attached to a metal cation. Therefore, the phosphate group acts as an anion. The overall charge of this anion is -3. This indicates that this anion can participate in the formation of monobasic, dibasic, and tribasic salts. The phosphate group has a tetrahedral arrangement. Inorganic phosphates occur naturally as the salts of group 1 elements. ex: sodium (Na), potassium (K), calcium (Ca), etc.
Figure 01: The Chemical Structure of Phosphate Anion
The two major inorganic phosphate compounds are orthophosphates and condensed phosphates. Among them, orthophosphates are very reactive, and these are the simplest inorganic phosphates. They contain only one phosphate unit per molecule. Condensed phosphates contain more than one phosphate unit. These compounds are also useful as fertilizers, ex: Superphosphate and Triple superphosphate.
What is Pyrophosphate (PPi)?
Pyrophosphate is a phosphorous oxyanion consisting of two phosphorous atoms in the form of P-O-P linkage. There are many different pyrophosphate salts, including disodium pyrophosphate and tetrasodium pyrophosphate. We can describe pyrophosphate as a diphosphate as well because it appears like two phosphate groups are attached to each other. Moreover, the parent pyrophosphate molecules are derived from partial or complete neutralization of pyrophosphoric acid.
Figure 02: The Chemical Structure of Pyrophosphate
We can prepare a pyrophosphate compound by heating phosphates. However, pyrophosphate salts are industrially produced by phosphoric acid to an extent where a condensation reaction takes place. Furthermore, these compounds generally appear in white or are colorless. Among these salts, pyrophosphates associated with alkali metals are water-soluble substances. Also, these salts are important as complexing agents for metal ions. Therefore, pyrophosphates have many important applications in the chemical industry.
What is the Difference Between Inorganic Phosphate (Pi) and Pyrophosphate (PPi)?
Inorganic phosphates are salts of phosphoric acid. In these compounds, we can see a phosphate group attached to a metal cation. Pyrophosphate is a phosphorous oxyanion consisting of two phosphorous atoms in the form of P-O-P linkage. The key difference between inorganic phosphate (Pi) and pyrophosphate (PPi) is that inorganic phosphate compounds can be found as a phosphate group attached to metal cation(s), whereas pyrophosphates can be found as two phosphate groups linked to each other through a P-O-P linkage and the anion is associated with metal cation(s).
The following table presents the difference between inorganic phosphate (Pi) and pyrophosphate (PPi) in more detail.
Summary – Inorganic Phosphate (Pi) vs Pyrophosphate (PPi)
Inorganic phosphates and pyrophosphates are two different types of phosphates derived compounds. The key difference between inorganic phosphate (Pi) and pyrophosphate (PPi) is that inorganic phosphate compounds can be found as a phosphate group attached to metal cation(s), whereas pyrophosphates can be found as two phosphate groups linked to each other through a P-O-P linkage and the anion is associated with metal cation(s).
Reference:
1. Maier, Karyn, et al. “What Is Pyrophosphate?” Info Bloom, 27 Jan. 2021.
2. “Pyrophosphate.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Phosphat-Ion” By NEUROtiker ⇌ – Own work (Public Domain) via Commons Wikimedia
2. “Pyrophosphate anion” By Kemikungen – Own work (Public Domain) via Commons Wikimedia