2,4-Dichloro-3-nitropyridine
[CAS# 5975-12-2]

Identification

• Classification: Pharmaceutical intermediate >> Heterocyclic compound intermediate >> Pyridine compound >> Nitropyridine
• Name: 2,4-Dichloro-3-nitropyridine
• Molecular Formula: C₅H₂Cl₂N₂O₂
• Molecular Weight: 192.99
• CAS Registry Number: 5975-12-2
• EC Number: 688-499-7
• SMILES: C1=CN=C(C(=C1Cl)[N+](=O)[O-])Cl

Properties

• Solubility: 451.2 mg/L (25 °C water)
• Density: 1.6±0.1 g/cm³, Calc.^*
• Index of Refraction: 1.603, Calc.^*
• Melting point: 84.12 °C
• Boiling Point: 285.7±35.0 °C (760 mmHg), Calc.^*, 272.91 °C
• Flash Point: 126.6±25.9 °C, Calc.^*

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

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P264-P264+P265-P271-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H312
Skin sensitization	Skin Sens.	1	H317
Eye irritation	Eye Irrit.	2A	H319

Discovery and Applications

2,4-Dichloro-3-nitropyridine is a halogenated nitro-substituted heterocyclic compound with the molecular formula C₅HCl₂ClN₂O₂. Its chemical structure consists of a pyridine ring bearing chlorine atoms at the 2- and 4-positions and a nitro group (–NO₂) at the 3-position. This compound belongs to the class of chloronitropyridines, which are important intermediates in agrochemical and pharmaceutical synthesis due to their reactivity and functional group diversity.

The synthesis of 2,4-dichloro-3-nitropyridine typically involves the nitration of 2,4-dichloropyridine under controlled conditions using nitrating agents such as nitric acid or a mixture of nitric and sulfuric acids. The selective introduction of the nitro group at the 3-position requires careful control of reaction parameters to prevent over-nitration or unwanted substitution at other positions. Alternative synthetic routes may include halogenation of nitropyridine derivatives or regioselective substitution reactions starting from simpler precursors.

This compound is widely used as a versatile intermediate in the production of various agrochemicals, pharmaceuticals, and specialty chemicals. The presence of reactive chlorine atoms on the pyridine ring allows for nucleophilic aromatic substitution reactions, where the chlorines can be replaced by nucleophiles such as amines, thiols, or alkoxides to yield functionalized pyridine derivatives. The nitro group can undergo reduction to an amino group or participate in further transformations, expanding the compound's synthetic utility.

In agrochemical chemistry, derivatives of 2,4-dichloro-3-nitropyridine serve as precursors for herbicides, fungicides, and insecticides. The pyridine scaffold with electron-withdrawing substituents such as chloro and nitro groups confers biological activity or serves as a platform for constructing biologically active molecules. Its reactivity enables the design and synthesis of compounds with enhanced selectivity and potency against target pests.

Pharmaceutical applications include the use of 2,4-dichloro-3-nitropyridine as a building block for the synthesis of heterocyclic drugs and bioactive molecules. The compound's chemical properties allow for the construction of pyridine-containing frameworks that are common in medicinal chemistry due to their ability to interact with biological targets through hydrogen bonding, π-stacking, and other interactions.

Analytical characterization of 2,4-dichloro-3-nitropyridine involves nuclear magnetic resonance (NMR) spectroscopy, which provides detailed information on the substitution pattern of the pyridine ring and confirms the positions of chlorine and nitro substituents. Infrared (IR) spectroscopy detects characteristic absorption bands of the nitro group and aromatic ring. Mass spectrometry (MS) is employed to determine molecular weight and fragmentation patterns, while chromatographic techniques such as high-performance liquid chromatography (HPLC) assess purity and monitor reaction progress.

Safety considerations for 2,4-dichloro-3-nitropyridine reflect those typical for chlorinated nitroaromatic compounds. It is potentially hazardous if inhaled, ingested, or absorbed through the skin and may cause irritation to the respiratory tract, skin, and eyes. Handling requires appropriate protective measures including gloves, protective clothing, and eye protection, as well as working in well-ventilated areas or under fume hoods to minimize exposure.

In summary, 2,4-dichloro-3-nitropyridine is a significant chloronitropyridine intermediate widely utilized in agrochemical and pharmaceutical synthesis. Its structural features provide multiple reactive sites for chemical modification, enabling the development of a broad range of biologically active compounds. Well-established synthetic methods and analytical techniques support its application in industrial and research settings while ensuring safe handling practices.

References

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