Imidacloprid

1.Chemical and Physical Properties

1.1 Chemical Identity

• Common Name: Imidacloprid
• Chemical Name (IUPAC): 1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine
• CAS Registry Number: 138261-41-3 (for imidacloprid); 105827-78-9 (for an earlier CAS number sometimes cited)
• Chemical Class: Neonicotinoid insecticide (specifically a chloronicotinyl insecticide)
• Molecular Formula: C₉H₁₀ClN₅O₂
• Molecular Weight: 255.66 g/mol

1.2 Key Physical Properties

• Appearance: Colorless crystals or white to off-white crystalline powder.
• Odour: Weak, characteristic odour, or odourless.
• Melting Point: Approximately 144°C (decomposes slightly before melting).
• Boiling Point: Decomposes before boiling at atmospheric pressure.
• Vapour Pressure: Very low (e.g., ~4 x 10⁻⁷ Pa or ~3 x 10⁻⁹ mmHg at 20°C), indicating it is non-volatile.
• Density: Approximately 1.54 g/cm³ at 20°C.
• Solubility:
  • Water: Moderately soluble; 0.61 g/L (610 ppm) at 20°C. Solubility is pH-dependent.
  • Organic Solvents: Soluble in dichloromethane; slightly soluble in methanol, ethanol, isopropanol, acetone, toluene; very slightly soluble in n-hexane.
• Log K_ow (Octanol-Water Partition Coefficient): Typically around 0.57, indicating low potential for bioaccumulation in fatty tissues but high systemic movement in plants.

1.3 Key Chemical Properties

• Stability:
  • Stable to hydrolysis at pH 5-11.
  • Relatively stable to photolysis in water, but can degrade on soil surfaces exposed to light.
  • Stable under normal storage conditions.
• Corrosivity: Non-corrosive.

2.Production Technologies

2.1 Synthesis Overview

1. Synthesis of 6-chloronicotinaldehyde or 6-chloropyridine-3-carboxaldehyde: This is a key intermediate. It can be prepared from picoline derivatives or other pyridine precursors through chlorination and oxidation steps.
2. Synthesis of N-nitroimidazolidine-2-ylideneamine or its precursor: This part involves the reaction of ethylenediamine with a cyanogen halide (like cyanogen bromide) or carbon disulfide, followed by reactions to form the imidazolidine ring and introduce the nitroimine group.
3. Condensation Reaction: The 6-chloropyridylmethylamine (derived from 6-chloronicotinaldehyde by reductive amination or by reacting 6-chloro-3-(chloromethyl)pyridine with an amine source) is reacted with the N-nitroimidazolidine-2-ylideneamine derivative (e.g., 2-nitroiminoimidazolidine) to form imidacloprid.
   1. A common intermediate is 6-chloro-3-(chloromethyl)pyridine, which is reacted with N-(2-aminoethyl)-N'-nitroguanidine or similar compounds.

2.2 Key Raw Materials

• Pyridine derivatives (e.g., 3-picoline)
• Chlorinating agents (e.g., chlorine gas, sulfuryl chloride)
• Ethylenediamine
• Cyanogen halides (e.g., cyanogen bromide) or carbon disulfide
• Nitrating agents
• Various catalysts and solvents

2.3 Formulation

• Soluble Concentrate (SL)
• Seed Treatment (FS - Flowable Concentrate for Seed Treatment; WS - Wettable Powder for Slurry Seed Treatment): Very common use.
• Wettable Powder (WP)
• Water Dispersible Granules (WG or WDG)
• Granules (GR): For soil application.
• Tablets (TB)
• Suspension Concentrate (SC)
• Also found in ready-to-use (RTU) formulations for consumer products, baits, and combination products with other pesticides or fertilizers.

3.Applications

3.1 Mode of Action

• Imidacloprid is a systemic insecticide with translaminar activity (can move from one side of a leaf to the other).
• It belongs to the Group 4A insecticides according to the Insecticide Resistance Action Committee (IRAC).
• Mechanism: It acts as an agonist of the nicotinic acetylcholine receptor (nAChR) in the insect central nervous system. It binds to these receptors, causing a nerve impulse that cannot be shut off, leading to overstimulation, paralysis, and death of the insect.
• It is much more active on insect nAChRs than on mammalian nAChRs, which contributes to its selective toxicity.
• Uptake: Absorbed by roots (when soil-applied or used as seed treatment) and foliage, and translocated acropetally (upwards) within the plant xylem.

3.2 Crops

• It belongs to the Group 4A insecticides according to the Insecticide Resistance Action Committee (IRAC).
• Mechanism: It acts as an agonist of the nicotinic acetylcholine receptor (nAChR) in the insect central nervous system. It binds to these receptors, causing a nerve impulse that cannot be shut off, leading to overstimulation, paralysis, and death of the insect.
• It is much more active on insect nAChRs than on mammalian nAChRs, which contributes to its selective toxicity.
• Uptake: Absorbed by roots (when soil-applied or used as seed treatment) and foliage, and translocated acropetally (upwards) within the plant xylem.

3.3 Pests Controlled

• Aphids (various species)
• Whiteflies (e.g., Bemisia tabaci, Trialeurodes vaporariorum)
• Thrips (various species)
• Leafhoppers and Planthoppers
• Psyllids (e.g., Asian citrus psyllid)
• Some Beetles: Colorado potato beetle, flea beetles, Japanese beetle (adults).
• Soil Insects: Wireworms, grubs (when soil-applied or as seed treatment).
• Termites (for structural protection)
• Fleas (on pets)
• Limited activity against: Spider mites, nematodes, and most caterpillars (Lepidoptera).

4.Market Analysis

4.1 Global Market Overview

• Imidacloprid was once the world's best-selling insecticide and a flagship product of the neonicotinoid class.
• Its market share has been significantly impacted by regulatory restrictions related to bee toxicity, particularly in Europe and North America.
• However, it remains a widely used insecticide globally, especially in regions with less stringent regulations or for specific uses where alternatives are limited.
• Major original patent holder was Bayer CropScience (product names like Gaucho, Merit, Confidor, Admire). Many generic versions are now available.

4.2 Key Market Dynamics

• Drivers (Historically and in some current markets):
  • Broad-spectrum control of sucking pests.
  • Systemic activity and long-lasting protection (especially via seed treatment and soil application).
  • Versatility in application methods.
  • Relatively low use rates for some applications.
• Restraints/Challenges:
  • Bee Toxicity and Pollinator Concerns: The primary factor driving market decline and regulatory action.
  • Regulatory Bans and Restrictions: Significant impact in the EU, Canada, and some parts of the USA.
  • Insecticide Resistance: Resistance to imidacloprid and other neonicotinoids has been documented in several key pest species (e.g., Colorado potato beetle, some aphid species, whiteflies).
  • Public Perception: Negative public perception of neonicotinoids due to their impact on pollinators.
  • Competition: From newer insecticide classes, biological control agents, and integrated pest management (IPM) strategies. There is a market shift towards insecticides with better environmental profiles

5.Upstream and Downstream Linkages

5.1 Upstream Linkages (Inputs for production)

• Basic Petrochemicals: As precursors for pyridine rings and other organic intermediates.
• Chlorinating Agents.
• Ethylenediamine, Cyanogen Halides/Carbon Disulfide: For the imidazolidine moiety.
• The chemical industry provides these basic building blocks

5.2 Downstream Linkages (outputs and consumers)

• Agrochemical Formulators: Purchase technical grade imidacloprid to produce end-use products.
• Seed Companies: Incorporate imidacloprid into seed treatments.
• Pest Control Operators (PCOs): For termite control and other structural pest management.
• Veterinary Medicine Companies: For flea control products.
• Distributors and Retailers: Supply formulated products to farmers and consumers.
• Farmers and Growers: The primary end-users in agriculture and horticulture.
• Homeowners: For garden pest control and pet care products.