5-Chloro-2-Pentanone (CAS No. 5891-21-4)

5-Chloro-2-pentanone, also known as 5-chloropentan-2-one or methyl 3-chloropropyl ketone, is a halogenated ketone serving as a valuable intermediate in organic synthesis. With the chemical formula C₅H₉ClO, it is a colorless to pale yellow liquid with a characteristic ketone odor. This compound is prized for its reactivity in nucleophilic substitutions and cyclization reactions, making it essential in the production of pharmaceuticals, agrochemicals, and fine chemicals. Its chloroalkyl chain provides versatility for further derivatization, supporting efficient multi-step syntheses.

CAS Number: 5891-21-4 Molecular Weight: 120.58 g/mol Synonyms: 5-Chloropentan-2-one, 3-Acetylpropyl chloride, 1-Chloro-4-pentanone

Key Properties

5-Chloro-2-pentanone offers consistent physical and chemical traits that align with its role in synthetic processes. The table below details primary specifications:

Property Value/Description
Appearance Colorless to pale yellow liquid
Purity ≥90.0% (GC)
Density (25°C) 1.057 g/cm³
Boiling Point 71-72°C (20 mmHg)
Melting Point <-20°C (liquid at room temperature)
Flash Point 35.6°C (closed cup)
Refractive Index (20°C) 1.438
Solubility in Water Slightly soluble (≈5 g/L at 20°C)
Vapor Pressure (25°C) 1.31 mmHg

These properties indicate its volatility and compatibility with organic solvents, ideal for distillation and reaction workups.

Applications and Uses

5-Chloro-2-pentanone’s dual functional groups (ketone and chloride) enable broad utility in chemical manufacturing:

  • Pharmaceutical Intermediates: Key precursor for synthesizing anti-COVID-19 therapeutics and other antiviral agents through substitution and cyclization with hydrazines or amines.
  • Agrochemical Synthesis: Used in the preparation of herbicides and insecticides, where the chloroalkyl moiety facilitates ring closure to form heterocyclic structures.
  • Fine Chemicals: Serves as a building block for fragrances like octamethol and in the production of surfactants via alkylation reactions.
  • Organic Research: Employed in nucleophilic displacement reactions and as a reagent for generating enolates in carbon-carbon bond formations.
  • Polymer Additives: Incorporated in the synthesis of functionalized monomers for specialty polymers with enhanced reactivity.

Its stability under mild conditions supports scalable production in both lab and industrial settings.

Safety and Handling

It is flammable and irritating, classified as a harmful substance if ingested. It may cause skin/eye irritation and respiratory discomfort upon exposure. Primary guidelines include:

  • Storage: Store in a cool, dry, well-ventilated area away from ignition sources, oxidizers, and strong bases. Use glass or Teflon-lined containers; stabilize with K₂CO₃ if needed.
  • Handling: Wear PPE such as gloves, goggles, and respirators. Use in a fume hood; avoid inhalation and skin contact. Ground equipment to prevent static discharge.
  • Environmental Impact: Toxic to aquatic life; contain spills with absorbents and dispose per hazardous waste regulations to minimize release.
  • Regulatory Compliance: GHS classifications: H226 (flammable), H302 (harmful if swallowed), H315/H319 (skin/eye irritant), H335 (respiratory irritant). Complies with REACH and TSCA.

Request the Safety Data Sheet (SDS) for complete hazard details.

Frequently Asked Questions (FAQs)

What is the primary use of it?

5-Chloro-2-pentanone is mainly utilized as a pharmaceutical intermediate, particularly in the synthesis of antiviral drugs and heterocycles via cyclization reactions.

Is 5-Chloro-2-pentanone safe for industrial synthesis?

It is flammable and irritating, requiring PPE, ventilation, and ignition controls, but is safely handled in controlled environments with standard chemical protocols.

What is the shelf life of it?

Stored properly under stabilization in sealed containers at <25°C, it maintains stability for 12-18 months, with periodic testing for peroxide formation.

Can 5-Chloro-2-pentanone be shipped internationally?

Yes, it is shipped globally under UN 1992 (Class 3, PG III) regulations, in compatible drums or bottles for quantities from 100 g to bulk.

How does 5-Chloro-2-pentanone compare to 5-bromo-2-pentanone?

The chloro analog is less reactive in substitutions but more cost-effective and stable, making it preferable for large-scale pharma syntheses over the bromo variant.

Is 5-Chloro-2-pentanone soluble in organic solvents?

Yes, it is highly soluble in solvents like ethanol, acetone, and dichloromethane, but only slightly in water, aiding in extraction and purification steps.

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