Acetochlor

1.Chemical and Physical Properties

1.1Chemical Identity

• Common Name: Acetochlor
• Chemical Name (IUPAC): 2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide
• CAS Registry Number: 34256-82-1
• Chemical Class: Chloroacetamide herbicide (also classified as an anilide herbicide)
• Molecular Formula: C₁₄H₂₀ClNO₂
• Molecular Weight: 269.77 g/mol

1.2 Key Physical Properties

• Appearance:
  • Pure Acetochlor: Colorless to pale yellow oil or crystalline solid (depending on purity and temperature).
  • Technical Grade: Typically a dark brown or purple oily liquid.
• Odour: Mildly aromatic or sweetish odour.
• Melting Point:
• Boiling Point: Approximately 162°C at 67 Pa (0.5 mmHg). Decomposes at higher temperatures (e.g., >200°C).
• Vapour Pressure: Relatively low (e.g., 4.5 x 10⁻³ Pa or ~3.4 x 10⁻⁵ mmHg at 25°C), indicating moderate volatility.
• Density: Approximately 1.135 g/cm³ at 20°C.
• Solubility:
  • Water: Low solubility; approximately 223 mg/L (23 ppm) at 25°C.
  • Organic Solvents: Readily soluble in most organic solvents like acetone, ethanol, toluene, xylene, dichloromethane, ethyl acetate.
• Log K_ow (Octanol-Water Partition Coefficient): Typically around 3.03 - 3.53, indicating a moderate potential for bioaccumulation.

1.3 Key Chemical Properties

• Stability:
  • Relatively stable in neutral and weakly acidic media.
  • Hydrolyzes in strong alkaline (pH > 9) and strong acidic (pH
  • Stable to light under normal storage conditions.
  • Corrosivity: May be corrosive to some metals. Formulations often contain corrosion inhibitors.

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  2.Production Technologies

  2.1 Synthesis Overview

  Acetochlor is typically synthesized through a multi-step process involving the reaction of an aniline derivative with chloroacetyl chloride, followed by an alkoxylation step. A common route involves:
  1. Formation of 2-ethyl-6-methylaniline (EMA): This aniline derivative is a key precursor. It can be synthesized through various routes, often involving nitration, reduction, and alkylation of benzene or toluene derivatives.
  2. Acylation of EMA with Chloroacetyl Chloride: 2-ethyl-6-methylaniline reacts with chloroacetyl chloride (ClCOCH₂Cl) to form an intermediate N-(2-ethyl-6-methylphenyl)-2-chloroacetamide.
     1. C₆H₃(CH₃)(C₂H₅)NH₂ + ClCOCH₂Cl → C₆H₃(CH₃)(C₂H₅)NHCOCH₂Cl + HCl
  3. Alkoxymethylation (Ethoxymethylation): The chloroacetamide intermediate is then reacted with formaldehyde (or paraformaldehyde) and ethanol, typically under acidic conditions, to introduce the ethoxymethyl group (-CH₂OCH₂CH₃) onto the nitrogen atom.
     1. C₆H₃(CH₃)(C₂H₅)NHCOCH₂Cl + CH₂O + CH₃CH₂OH → C₆H₃(CH₃)(C₂H₅)N(CH₂OCH₂CH₃)COCH₂Cl + H₂O

2.2 Key Raw Materials

• 2-ethyl-6-methylaniline (EMA) or its precursors
• Chloroacetyl chloride
• Formaldehyde (or paraformaldehyde)
• Ethanol
• Catalysts (e.g., acid catalysts)
• Solvents

2.3 Formulation

• Technical grade acetochlor is rarely used directly. It is typically formulated into various products for agricultural use.
• Common formulations include:
  • Emulsifiable Concentrates (EC): Most common formulation type.
  • Granules (GR)
  • Microencapsulated (ME/CS) formulations: Designed to reduce volatility, operator exposure, and potentially improve weed control duration or crop safety.
• Formulations often contain adjuvants, solvents, emulsifiers, and sometimes safeners (to protect the crop).

3.Applications

3.1 Mode of Action

• Acetochlor is a selective, pre-emergence herbicide.
• It belongs to the Group 15 (K3) herbicides according to the Herbicide Resistance Action Committee (HRAC) and the Weed Science Society of America (WSSA).
• Mechanism: It inhibits the synthesis of very long-chain fatty acids (VLCFAs) in susceptible plants. This disruption affects cell division, cell growth, and the formation of cell membranes, particularly in developing seedlings.
• Uptake: Primarily absorbed by the emerging shoots (coleoptile in grasses, hypocotyl in broadleaves) of germinating weeds, and to a lesser extent by roots.
• Symptoms: Weeds usually fail to emerge from the soil or emerge stunted and distorted, then die shortly after.

3.2 Crops

• Maize (Corn): Its largest market.
• Soybeans: Use may be more restricted or require specific formulations/safeners in some regions.
• Cotton
• Peanuts
• Sugarcane
• Potatoes
• Sunflowers
• Other crops like some vegetables (e.g., brassicas, onions in some regions)

3.3 Weeds Controlled

• Annual Grasses:
  • Foxtails (Setaria spp.)
  • Barnyardgrass (Echinochloa crus-galli)
  • Crabgrass (Digitaria spp.)
  • Goosegrass (Eleusine indica)
  • Fall panicum (Panicum dichotomiflorum)
• Some Annual Broadleaf Weeds:
  • Pigweeds (Amaranthus spp.)
  • Lambsquarters (Chenopodium album)
  • Common ragweed (Ambrosia artemisiifolia) (suppression)
  • Nightshades (Solanum spp.)
  • Waterhemp (Amaranthus tuberculatus) (though resistance is an issue)
• Some Sedges:
  • Yellow nutsedge (Cyperus esculentus) (suppression or control)

4.Market Analysis

4.1 Global Market Overview

• Acetochlor is a widely used herbicide globally, particularly in corn-growing regions.
• Major markets include North America (USA), South America (Brazil, Argentina), Asia (China, India), and parts of Europe.
• It is a mature product, but still holds a significant market share due to its efficacy and relatively low cost for certain weed spectrums

4.2 Key Market Dynamics

• Drivers:
  • Effective control of key annual grasses and some broadleaf weeds in major crops like corn.
  • Cost-effectiveness compared to some newer herbicides.
  • Use in herbicide resistance management programs (when used appropriately in mixtures or rotations).
• Restraints/Challenges:
  • Regulatory Pressure: Due to carcinogenicity concerns and groundwater contamination potential, its use is restricted or banned in some countries/regions (e.g., banned in the European Union since 2012).
  • Herbicide Resistance: Increasing incidence of weed populations resistant to acetochlor and other Group 15 herbicides (e.g., waterhemp).
  • Environmental Concerns: Groundwater contamination and toxicity to non-target organisms.
  • Competition: From other chloroacetamides (e.g., metolachlor, alachlor - though alachlor use has declined more significantly), HPPD inhibitors, and other herbicide classes.
  • Development of Safer Formulations: Push towards microencapsulated or safened formulations to mitigate risks.

5.Upstream and Downstream Linkages

5.1 Upstream Linkages(Inputs for Production)

• Basic Petrochemicals: Benzene, toluene, ethylene (as precursors for alkyl groups and other intermediates).
• Chlorine and Acetic Acid derivatives: For chloroacetyl chloride.
• Formaldehyde and Ethanol: For the ethoxymethyl group.
• Ammonia: For aniline synthesis.
• The availability and cost of these chemical building blocks influence acetochlor production costs