Azoxystrobin

1.Chemical and Physical Properties

1.1 Chemical Identity

• Common Name: Azoxystrobin
• Chemical Name (IUPAC): methyl (αE)-2-[[6-(2-cyanophenoxy)-4-pyrimidinyl]oxy]-α-(methoxymethyl)benzeneacetate
  • Or more simply: methyl (E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate
• CAS Registry Number: 131860-33-8
• Chemical Class: Strobilurin fungicide (QoI - Quinone outside Inhibitor)
• Molecular Formula: C₂₂H₁₇N₃O₅
• Molecular Weight: 403.4 g/mol
• Development Code: ICIA5504 (from ICI/Zeneca, now Syngenta)
• Structure:
  • Azoxystrobin has a complex structure derived from naturally occurring strobilurins found in wood-rotting fungi (e.g., Strobilurus tenacellus). Key features include a β-methoxyacrylate toxophore (responsible for its fungicidal activity) linked to a (2-cyanophenoxy)pyrimidine side-chain.

1.2 Physical Properties

• Appearance:
  • Pure: White to pale beige crystalline solid or powder.
  • Technical Grade (>95%): Typically an off-white to light brown powder.
• Odour:
  • Faint, slightly sweetish or aromatic odour. Some describe it as almost odourless.
• Melting Point:
  • 116°C (may start to decompose if held at this temperature for extended periods or depending on polymorph). Some sources list ranges like 114-116°C or 118-119°C depending on purity and crystal form.
• Boiling Point: Decomposes before boiling at atmospheric pressure.
• Vapour Pressure: Very low.
  • Typically reported as:
    • 1.1 x 10⁻⁷ mPa (8.25 x 10⁻¹⁰ mmHg) at 20°C
    • 1.1 x 10⁻⁴ Pa (or 1.1 x 10⁻⁹ atm) at 25°C
  • This low vapour pressure indicates it is not readily volatile.
• Density: Approximately 1.33 - 1.34 g/cm³ at 20°C.
• Solubility:
  • Water: Low solubility.
    • 6.0 mg/L (or 6.7 mg/L) at 20°C or 25°C.
    • Its solubility is pH-independent over typical environmental pH ranges.
  • Organic Solvents (at 20-25°C):
    • Methanol: ~20 g/L
    • Acetone: >200 g/L (or ~100-200 g/L)
    • Ethyl acetate: ~56 g/L (or ~100-200 g/L)
    • Dichloromethane: >200 g/L (or >500 g/L)
    • Toluene: ~26 g/L (or ~50-100 g/L)
    • n-Hexane: ~0.056 g/L (or 0.03-0.1 g/L) - poorly soluble in aliphatic hydrocarbons.
    • Acetonitrile: ~80 g/L

1.3 Chemical Properties

• Stability:
  • Hydrolysis: Stable to hydrolysis under normal environmental pH conditions (pH 5, 7, and 9). DT₅₀ (half-life for hydrolysis) >30 days at 25°C across this pH range.
  • Photolysis/Photostability: Moderately susceptible to photolysis (degradation by sunlight).
    • In water: DT₅₀ can range from a few hours to several days depending on conditions (e.g., presence of sensitizers, light intensity). Typically reported as rapid (e.g., DT₅₀ ~11-17 hours in aqueous solution exposed to simulated sunlight).
    • On soil surfaces: Also undergoes photolytic degradation, with DT₅₀ values of several days.
  • Thermal Stability: Stable at ambient temperatures. As noted, it melts around 116°C and may start to decompose if held at temperatures near or above its melting point for extended periods.
• Reactivity:
  • Not considered highly reactive with common materials.
  • Not corrosive.
  • Can be degraded by strong oxidizing agents or strong acids/bases under harsh conditions (not typical environmental conditions).

2.Production Technologies (synthesis and Formulation)

2.1 Chemical Synthesis

• General Approach:
  • A multi-step process typically involving the reaction of key intermediates like 2-hydroxybenzonitrile and 4,6-dichloropyrimidine, followed by coupling and formation of the β-methoxyacrylate toxophore.
• Key Considerations:
  • Stereochemical control (E-isomer is active), high purity requirements (≥95% for technical grade), and increasingly, green chemistry principles.
• Development:
  • Originally synthesized by ICI/Zeneca (now Syngenta); various alternative routes have been developed by other companies post-patent expiry.

2.2 Technical Production Process

• Scale & Equipment:
  • Industrial production occurs in batch or continuous-flow reactors with systems for temperature control, mixing, separation, and purification.
• Quality Control:
  • Rigorous testing for chemical purity, isomer ratio, specified impurities, and physical properties.
• Environmental
  • Aspects: Focus on solvent recovery, waste stream management, and minimizing emissions and worker exposure

2.3 Formulation Technologies

• Common Types:
  • Primarily Suspension Concentrates (SC, e.g., 250 g/L), Water Dispersible Granules (WG/WDG, e.g., 50%), and Seed Treatment formulations (FS). Also used in mixtures.
• Key Components:
  • Active ingredient, water/solvents, surfactants, dispersants, anti-freeze agents, preservatives, and sometimes specific adjuvants like film-formers or colorants for seed treatments.
• Purpose:
  • To provide a stable, effective, and easy-to-use product tailored for specific application methods and crops. Mixtures with other active ingredients are common to broaden spectrum and manage resistance.

3.Applications

3.1 Biological Mode of Action

• Mechanism:
  • Azoxystrobin is a Quinone outside Inhibitor (QoI) fungicide (FRAC Group 11). It inhibits mitochondrial respiration by binding to the Qo site of cytochrome b, blocking electron transfer and ATP synthesis in fungi.
• Effects:
  • Prevents spore germination, mycelial growth, and sporulation of target fungi.
• Plant Interaction:
  • Exhibits translaminar (across the leaf) and acropetal systemic (upward in xylem) movement, protecting new growth.

3.2 Agricultural Applications

• Crop Spectrum:
  • Widely used on cereals (wheat, rice), fruits (grapes, apples), vegetables (tomatoes, potatoes), row crops (soybeans, corn), and specialty crops (turf, ornamentals).
• Disease Spectrum:
  • Broad-spectrum activity against Ascomycetes (powdery mildews), Basidiomycetes (rusts), Deuteromycetes (leaf spots), and some Oomycetes (downy mildews).
• Application:
  • Primarily via foliar spray, but also through seed treatment and soil application. Best used preventatively or at very early stages of infection.
• Resistance Management:
  • High risk of resistance; requires rotation or mixture with fungicides of different modes of action.

3.3 Non-Agricultural Applications

• Turf and Ornamentals:
  • Significant use in professional turf management (golf courses, sports fields) and in ornamental plant production for controlling various fungal diseases.
• Specialized Uses:
  • Limited applications in post-harvest treatment of fruits/vegetables in some regions, and very specific uses in forestry or aquaculture. Not a major material protection agent.

4.Market Analysis

4.1 Global Market Overview

• Size & Position:
  • One of the world's leading fungicides, with annual sales typically exceeding $1 billion. A key product within the strobilurin (QoI) market segment.
• Growth Trends:
  • Mature product. Growth is modest, driven by demand in emerging markets, new formulations/mixtures, and evolving disease pressures. Patent expirations have led to increased generic competition.
• Regional Demand:
  • Strong demand in Asia-Pacific (largest market), North America, Europe, and Latin America, with applications varying by regional cropping patterns

4.2 Key Market Dynamics

• Drivers:
  • Broad-spectrum efficacy, plant health benefits beyond disease control, versatility across many crops, and relative safety profile compared to older chemistries. Generic availability has increased accessibility.
• Restraints/Challenges:
  • Widespread development of pathogen resistance, increasing regulatory scrutiny (especially in Europe), environmental concerns regarding aquatic toxicity, and competition from newer fungicide classes

4.3 Competitive Landscape

• Innovator:
  • Syngenta remains a key player with branded products and mixtures.
• Generic Market:
  • Numerous generic manufacturers globally (e.g., ADAMA, UPL, various Chinese and Indian companies) offer azoxystrobin, increasing price competition.
• Strategies:
  • Innovators focus on premium formulations and mixtures; generic players compete on price and market access.

5.Upstream and Downstream Linkages

5.1 Upstream Linkages (Inputs for Production)

• Raw Materials:
  • Key chemical intermediates such as 2-hydroxybenzonitrile, substituted phenols, pyrimidine derivatives, various reagents (bases, catalysts), and solvents (e.g., DMF, toluene).
• Supply Chain:
  • Sourcing of intermediates often from specialized chemical manufacturers, with China and India being significant producers.
• Technology & Equipment:
  • Requires specialized chemical reactors, separation and purification equipment, and analytical instrumentation for quality control.

5.2 Downstream Linkages (outputs and Consumers)

• Primary Users:
  • Farmers (large-scale and specialty crop growers), turf managers, and agricultural cooperatives.
• Distribution Channels:
  • Agricultural input retailers, distributors, direct sales to large operations, and increasingly online platforms.
• End-Product Connection:
  • Impacts the quality and quantity of food (grains, fruits, vegetables) and ornamental products. Adherence to Maximum Residue Limits (MRLs) is crucial for trade.
• Supporting Services:
  • Relies on crop consultants, application services, and IPM programs for effective and responsible use.