Quintozine
[CAS# 82-68-8]

Identification

• Classification: Biochemical >> Plant extracts
• Name: Quintozine
• Synonyms: Pentachloronitrobenzene
• Molecular Formula: C₆Cl₅NO₂
• Molecular Weight: 295.34
• CAS Registry Number: 82-68-8
• EC Number: 201-435-0
• SMILES: C1(=C(C(=C(C(=C1Cl)Cl)Cl)Cl)Cl)[N+](=O)[O-]

Properties

• Density: 1.8±0.1 g/cm³ Calc.^*
• Melting point: 140 - 143 °C (Expl.)
• Boiling point: 328.0 °C 760 mmHg (Calc.)^*, 328 °C (Decomposes) (Expl.)
• Flash point: 161.6±26.5 °C (Calc.)^*
• Index of refraction: 1.63 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07;GHS09 Warning
• Risk Statements: H317-H400-H410
• Safety Statements: P261-P272-P273-P280-P302+P352-P321-P333+P317-P362+P364-P391-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Skin sensitization	Skin Sens.	1	H317
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400

• Transport Information: UN 2588; UN 3077

Discovery and Applications

Quintozine is a synthetic chemical compound classified as a triazine herbicide, widely used in agriculture for its effectiveness in controlling broadleaf weeds and certain grasses. It was developed during the mid-20th century as part of efforts to create selective herbicides that could protect crops while minimizing damage to desirable plants.

The chemical structure of quintozine is based on a triazine ring, a six-membered heterocyclic compound containing three nitrogen atoms. This structure is common among several herbicides known for inhibiting photosynthesis in susceptible plants. Quintozine acts primarily by interfering with the photosystem II (PSII) complex within chloroplasts. It binds to the D1 protein of PSII, blocking electron transport during the light-dependent reactions of photosynthesis. This disruption results in the inhibition of energy production, ultimately causing the death of targeted weeds.

Quintozine is valued for its selective herbicidal activity, which allows it to be used safely in a variety of crops such as cereals, corn, and soybeans. Its application typically involves pre-emergence or early post-emergence treatment, targeting weed seedlings before they can compete effectively with the crop plants. The compound's soil activity also contributes to its long-lasting weed control.

Environmental considerations have accompanied the use of quintozine, as its persistence in soil and potential toxicity to non-target organisms have been studied. While it demonstrates moderate persistence, degradation occurs through microbial activity and chemical hydrolysis, leading to the formation of less active metabolites. Regulatory agencies have established guidelines to manage its use and minimize environmental impact, including restrictions on application rates and timing.

Resistance development in weed populations is a recognized challenge with triazine herbicides like quintozine. Certain weed species have evolved mutations in the D1 protein that reduce binding affinity for the herbicide, rendering it less effective. This has led to the recommendation of integrated weed management practices to delay resistance and maintain herbicide efficacy.

In agricultural practice, quintozine is often used in combination with other herbicides or as part of crop management strategies to optimize weed control while reducing reliance on a single mode of action. Its role remains significant in maintaining crop yields and reducing labor-intensive weed control measures.

In summary, quintozine is a triazine herbicide discovered as a selective weed control agent, functioning through inhibition of photosystem II in plants. Its agricultural applications are balanced by considerations of environmental safety and resistance management, reflecting its established position in crop protection practices.

References

1979. Pesticide residue levels in soils and crops from 37 states, 1972--National Soils Monitoring Program (IV). Pesticides Monitoring Journal, 12(4).
URL: https://pubmed.ncbi.nlm.nih.gov/461116

2007. Pesticides in Western Canadian Mountain Air and Soil. Environmental Science & Technology, 41(17).
DOI: 10.1021/es070848o

2019. Organochlorine pesticides in the surrounding soils of POPs destruction facility: source fingerprinting, human health, and ecological risks assessment. Environmental Science and Pollution Research International, 27(6).
DOI: 10.1007/s11356-019-07183-7