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Trichlorophosphane: Reactivity Preparation and Uses in Industry

Phosphorus Trichloride: A Comprehensive Guide to Its Chemical Properties and Preparation

Phosphorus trichloride is an inorganic compound with the chemical formula PCl3. It is a colorless or yellow liquid with a pungent odor.

In this article, we will discuss the chemical properties and preparation of phosphorus trichloride.

Chemical Properties

Phosphorus trichloride has a molar mass of 137.33 g/mol, a molar density of 1.574 g/cm3, and a viscosity of 0.65 cP at 0°C and 0.438 cP at 50°C. Its melting point is -93.6°C, and its boiling point is 76.1°C.

At room temperature, it is a liquid.

Phosphorus trichloride is a covalent compound with covalent bonds between non-metals.

Its electron configuration and oxidation states are 1s2 2s2 2p6 3s2 3p3 and +1, +3, and +5, respectively. It has a trigonal pyramidal crystal structure with a bond angle of 107.3°. It is a polar molecule with a dipole moment of 0.975 D.

It can conduct electricity when dissolved in water or other polar solvents.

Phosphorus trichloride is acidic and acts as a Lewis base.

It reacts with acid to form an acyl chloride and with base to form ethanol and R3N. It also reacts with oxide to form phosphorus oxychloride and sulfur dioxide.

Phosphorus trichloride has hydrolysis, and upon reaction with water, it forms phosphorous acid. It has a paramagnetic property and is diamagnetic.

Preparation

Phosphorus trichloride is prepared by the reaction between white phosphorus and chlorine gas. The reaction occurs at room temperature and pressure and can be initiated by light or heat.

The balanced chemical equation is given as follows:

P4 (s) + 6Cl2 (g) 4PCl3 (l)

The enthalpy of formation of phosphorus trichloride is -319.7 kJ/mol.

The preparation process is rapid and exothermic.

It requires careful handling because the reactants are highly reactive. The reaction produces a toxic and corrosive gas called phosphorus pentachloride (PCl5), which needs to be removed by distillation.

Trigonal Pyramidal Shape

Phosphorus trichloride has a trigonal pyramidal shape. This shape results from the presence of three bonding pairs and one non-bonding pair of electrons in its valence shell.

The three bonding pairs are placed at the corners of a trigonal plane, and the non-bonding pair is at the top of the pyramid.

The presence of the non-bonding pair makes the molecule polar, which gives rise to its unique chemical and physical properties.

The dipole moment of phosphorus trichloride is directed towards the non-bonding pair and away from the bonded pairs.

Conclusion

Phosphorus trichloride is an essential chemical compound used in various industrial, agricultural, and pharmaceutical applications. It is used in the production of herbicides, insecticides, plasticizers, and flame retardants.

It is also used in the synthesis of organic compounds such as esters, amides, and acid chlorides.

In conclusion, the chemical properties and preparation of phosphorus trichloride have been discussed in this article.

Its unique trigonal pyramidal shape and polar nature give rise to its distinct properties. The reaction between white phosphorus and chlorine gas is the primary method used to prepare it.

Phosphorus trichloride has many applications and is widely used in the chemical industry.

Naming and Identification of Trichlorophosphane

Trichlorophosphane is an inorganic compound with the chemical formula PCl3. It is also known as phosphorus trichloride or phosphorus (III) chloride.

According to the IUPAC naming system, it is referred to as trichlorophosphane. It has a ChemSpider ID of 22798.

In this article, we will discuss the properties and characteristics of trichlorophosphane.

Strong Odour

Trichlorophosphane has a strong, pungent odor that is similar to the smell of hydrochloric acid. The strong odor of trichlorophosphane can cause respiratory problems if inhaled for an extended period.

Hence, it is essential to handle the compound only in well-ventilated areas or use appropriate personal protective equipment.

Central Atom and Surrounding Atoms

Trichlorophosphane contains one phosphorus atom and three chlorine atoms. The phosphorus atom, which is the central atom, has three unpaired electrons in its valence shell.

The surrounding chlorine atoms have an electronegativity of 3.16 and are covalently bonded to the phosphorus atom.

Due to the presence of highly electronegative atoms surrounding the central atom, trichlorophosphane is highly reactive towards many substances.

It readily undergoes hydrolysis to form phosphorus oxychloride and hydrochloric acid when exposed to moisture.

Physical and Chemical Properties

Trichlorophosphane is a colorless or yellow liquid with a boiling point of 76.1°C.

It has a density of 1.57g/cm3 and can dissolve in various organic solvents like ether and benzene. Trichlorophosphane is soluble in water, although it is extremely reactive in aqueous solutions.

Trichlorophosphane is considered a Lewis acid because it can accept a pair of electrons from a Lewis base. The compound can react violently with strong Lewis bases or nucleophiles such as water, alcohols, and ammonia.

This reactivity makes trichlorophosphane useful in organic synthesis since it can transform alcohols and carboxylic acids into the corresponding acyl chlorides via the Friedel-Crafts reaction.

Chemical Formula and Structure

The chemical formula for trichlorophosphane is PCl3. The molecular structure of trichlorophosphane is of great importance in understanding its chemical and physical properties.

The shape of trichlorophosphane is described as being trigonal pyramidal.

The central phosphorus atom contains three unshared electron pairs and three CH bond pairs.

The three chlorine atoms are located at the vertices of the pyramid. Due to the presence of the unshared electron pairs on the phosphorus atom, trichlorophosphane has a relatively high dipole moment, making it a polar molecule.

Applications of Trichlorophosphane

Trichlorophosphane is used in the chemical industry as a catalyst, reducing agent, and intermediate in many chemical reactions. For instance, it is used to manufacture organophosphorus pesticides, herbicides, and plasticizers.

Trichlorophosphane reduces metal salts to their elemental form. For example, trichlorophosphane reduces silver salts to silver atoms, and this effect has been utilized in photographic films.

Additionally, trichlorophosphane reacts with lithium and potassium organyls to form lithium alkyls and potassium alkyls, which are useful in synthetic chemistry.

Conclusion

Trichlorophosphane is a highly reactive inorganic compound with numerous applications in various industries. It has a strong odor and is a polar molecule with a trigonal pyramidal shape.

It can be toxic and corrosive, and therefore, it is critical to handle the compound with care. Trichlorophosphane is a powerful reducing agent and a Lewis acid, and its properties make it useful in organic synthesis.

Reactions and Uses of Trichlorophosphane

Trichlorophosphane is a versatile compound with many applications in the chemical industry. It reacts with various organic and inorganic substances, resulting in a range of products.

In this article, we will discuss the organic acid, base, oxide reactions, hydrolysis, and rubber metal deposition of trichlorophosphane.

Organic Acid Reaction

Trichlorophosphane reacts with organic acids to form acyl chlorides, also known as acid chlorides. The reaction, which can be catalyzed by a tertiary amine, is called the Friedel-Crafts acylation.

In this reaction, trichlorophosphane acts as a catalyst and a reactant.

The reaction occurs through electrophilic attack of the carbonyl group in the organic acid by the trichlorophosphane.

The result is the substitution of the OH group of the organic acid with a Cl group from trichlorophosphane, forming the acyl chloride. This reaction has wide applications in the synthesis of esters, amides, and other organic compounds.

Base Reaction

Trichlorophosphane reacts with a base, such as triethylamine (R3N), to form a salt, releasing hydrogen chloride gas. The reaction is an example of a neutralization reaction.

The reaction can be used for removing the trichlorophosphane byproduct in the synthesis of acid chlorides.

The reaction occurs through a nucleophilic attack by the nitrogen atom of the base on the electrophilic phosphorus atom of the trichlorophosphane molecule.

The result is the substitution of each chlorine atom of PCl3 by an alkyl group from R3N, forming the salt.

Oxide Reaction

Trichlorophosphane reacts with sulfur trioxide to form phosphorus oxychloride. This reaction is an example of an acid anhydride formation reaction.

The reaction occurs in two steps, where first, the sulfur trioxide reacts with the trichlorophosphane forming the intermediate compound, sulfuryl trichloride. In the second step, the sulfuryl trichloride reacts further to form phosphorus oxychloride.

Phosphorus oxychloride is used in the manufacture of many organic compounds such as dyes, herbicide, and pharmaceuticals.

Rubber Metal Deposition

Trichlorophosphane can be used in the deposition of metals onto rubber. The process involves dissolving trichlorophosphane in a polar solvent such as toluene or xylene, then immersing the rubber surface in the solution.

Metal ions are then introduced into the solution, and trichlorophosphane reacts with them to form a metal-trichlorophosphane complex.

The metal ions are then reduced in situ on the surface of the rubber with NaBH4 or LiAlH4, leading to the deposition of the metal on the rubber surface.

This method is known as surface-initiated polymerization, and it is useful in enhancing the mechanical, thermal, and electrical properties of rubber.

Hydrolysis

Trichlorophosphane readily undergoes hydrolysis, especially in the presence of water or protic solvents like alcohols. The reaction results in the formation of phosphorus oxychloride and hydrochloric acid.

The hydrolysis reaction limits the stability of trichlorophosphane in aqueous solutions. The reaction of trichlorophosphane with water can be hazardous, especially if the reaction is rapid and exothermic.

Reactive groups such as trichlorosilane, trimethylaluminum, and triethylaluminum can be used to selectively hydrolyze the trichlorophosphane without reacting with the other groups.

Conclusion

Trichlorophosphane is a unique compound with many applications in the chemical industry. It reacts with organic and inorganic substances, resulting in a range of products that are useful in various applications.

Its reactions with organic acids to form acyl chlorides and bases to form salts are used in many synthetic routes. Additionally, trichlorophosphane is useful in metal deposition on rubbers via surface-initiated polymerization.

The compound tends to undergo hydrolysis when exposed to water, leading to the formation of phosphorus oxychloride and hydrochloric acid. In conclusion, trichlorophosphane is a versatile compound with significant applications in the chemical industry.

Its reactions with organic acids, bases, oxides, and hydrolysis produce various products used in synthesis and manufacturing. Furthermore, trichlorophosphane can enhance the properties of rubber through metal deposition.

Understanding the reactivity and uses of trichlorophosphane is crucial for researchers and professionals in fields such as organic synthesis, materials science, and chemical manufacturing. Overall, trichlorophosphane plays a vital role in numerous processes, making it a key topic in the chemical industry.

FAQs:

  1. What is the primary role of trichlorophosphane in organic synthesis?
  2. Trichlorophosphane serves as a catalyst and reactant in the Friedel-Crafts acylation, allowing the conversion of organic acids into acyl chlorides, a vital step in many synthesis routes.

  3. How does trichlorophosphane react with bases?
  4. Trichlorophosphane reacts with bases, such as triethylamine (R3N), resulting in the formation of a salt and hydrogen chloride gas.

  5. What is the significance of trichlorophosphane’s reaction with oxides?
  6. Trichlorophosphane reacts with sulfur trioxide to form phosphorus oxychloride, an important compound used in the production of dyes, herbicides, and pharmaceuticals.

  7. How does trichlorophosphane contribute to metal deposition on rubber?
  8. Trichlorophosphane, when dissolved in a polar solvent, facilitates the deposition of metals onto rubber surfaces, improving their mechanical, thermal, and electrical properties.

  9. What happens when trichlorophosphane undergoes hydrolysis?
  10. When exposed to water or protic solvents, trichlorophosphane undergoes hydrolysis, leading to the formation of phosphorus oxychloride and hydrochloric acid. Remember, trichlorophosphane’s reactivity and versatile applications make it a crucial compound in various industries, requiring proper handling and understanding of its properties and reactions.

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