Inorganic Hydrazine Derivatives

Synthesis, Properties and Applications

K. C. Patil, Tanu Mimani Rattan, K. C. Patil, Tanu Mimani Rattan

• Publisher: Wiley
• Year: 2014
• Print ISBN:
  9781118715130
• eBook ISBN:
  9781118693568
• Edition: 1
• Topic: Scienze fisiche
• Subtopic: Chimica inorganica

Traditionally, interest in the chemistry of hydrazine and its derivatives has been focused on the development of propellants and explosives, but in recent years a wide variety of new applications have emerged in fields such as polymers, pharmaceuticals, water treatment, agriculture and medicine. Inorganic Hydrazine Derivatives: Synthesis, Properties and Applications presents a comprehensive review of the research carried out in this field during the last four decades.

Methods for synthesizing inorganic hydrazine derivatives and complexes are systematically presented, together with details of their characterization, spectra, thermal analysis, crystal structure, and applications. Strong emphasis is given to controlling the reactivity of hydrazine derivatives from detonation to deflagration to decomposition. The monograph also highlights current developments and applications of inorganic hydrazine derivatives, including the synthesis of nanostructured materials.

Topics covered include:

• An introduction to hydrazine and its inorganic derivatives
• Hydrazine salts
• Metal hydrazines
• Metal hydrazine carboxylates
• Hydrazinium metal complexes
• Applications of inorganic hydrazine derivatives

This applications-based handbook is a valuable resource for academics and industry professionals researching and developing hydrazine compounds, high energy materials, nanomaterials, and pharmaceuticals.

1

Hydrazine and Its Inorganic Derivatives

Tanu Mimani Rattan¹ and K. C. Patil²

¹Department of Physics Sri Sathya Sai Institute of Higher Learning Prasanthi Nilayam, India

²Department of Inorganic and Physical Chemistry Indian Institute of Science Bangalore, India

1.1 Introduction

The chemistry of hydrazine (N₂H₄) acquires significance due to the presence of two free electron pairs and four substitutable hydrogen atoms, in addition to a potent N–N bond (Figure 1.1). Hydrazine is an endothermic molecule (ΔH_f = 55.63 kJ mol⁻¹) with nitrogen in the −2 valence state. Nitrogen's natural tendency is toward the attainment of a zero valence state as in N₂ molecule (

). As a result, it gives off nearly six times the energy as that stored in the N–N bond. A tremendous amount of energy (ca −622 kJ mol⁻¹) is released during the decomposition of N₂H₄ to N₂. This important energetic property of hydrazine was first recognized by the Germans during World War II when they used it as a rocket fuel. Since then hydrazine has been extensively used as a fuel in rocket motors because of its suitable physical properties, endothermicity, and extremely high reactivity with various oxidizers. The ignition of anhydrous hydrazine is achieved simply by passing it through a catalyst bed, producing completely gaseous products, making it an excellent fuel for monopropellant rockets. The other advantage of using hydrazine and its derivatives [e.g., monomethyl hydrazine (MMH) and unsymmetrical dimethyl hydrazine (UDMH)] as propellants stems from the fact that they ignite instantaneously. They are hypergolic on coming in contact with various liquid oxidizers such as HNO₃, N₂O₄, and so on. However, interest in hydrazine and its derivatives has now extended to applications in agriculture (pesticides and fungicides), blowing agents, boiler feed water treatment, pharmaceuticals, and in synthesizing nanostructures. The consumption of hydrazine produced for these latter applications far surpasses that used as rocket propellant.

Figure 1.1 Structure of the hydrazine molecule.

1.1.1 Properties of Hydrazine

Hydrazine is a strong base, although slightly weaker than ammonia as evident from the respective dissociation constants (k₁ and k₂) in aqueous solution (1.1) and (1.2). It is a much stronger nucleophile than ammonia. The second ionization constant shown in (1.2) being very small, suggests that the

cation exists at an extremely low pH:

(1.1)

(1.2)

In aqueous solutions hydrazine largely exists as the hydrazinium cation (

) while the hydrazonium cation (

) exists only in strong acidic conditions.

ion reacts completely with solvent water to give back

in accordance with the equation:

(1.3)

This suggests that the

ion does not readily exist in aqueous solutions.

1.1.1.1 Redox Properties

Hydrazine has two lone pairs of electrons on its nitrogen atoms. This makes it a strong reducing agent since it can donate all four electrons. The hydrazinium cation (

) also has a lone pair of electrons on its nitrogen atom and therefore acts as a...

Table of contents

• Cover
• Title Page
• Copyright
• Dedication
• List of Contributors
• Foreword
• Preface
• Acknowledgements
• Chapter 1: Hydrazine and Its Inorganic Derivatives
• Chapter 2: Hydrazine Salts
• Chapter 3: Metal Hydrazines
• Chapter 4: Metal Hydrazine Carboxylates
• Chapter 5: Hydrazinium Metal Complexes
• Chapter 6: Applications of Inorganic Hydrazine Derivatives
• Index