5-Chloro-2-pentanone
[CAS# 5891-21-4]

Identification

• Classification: Chemical reagent >> Organic reagent >> Fatty ketone (including enol)
• Name: 5-Chloro-2-pentanone
• Synonyms: 5-Chloropentan-2-one; Methyl 3-chloropropyl ketone
• Molecular Formula: C₅H₉ClO
• Molecular Weight: 120.58
• CAS Registry Number: 5891-21-4
• EC Number: 227-565-8
• SMILES: CC(=O)CCCCl

Properties

• Density: 1.053
• Boiling point: 172-175 °C
• Refractive index: 1.437-1.446
• Flash point: 35 °C

Safety Data

• Hazard Symbols: GHS02;GHS07 Warning
• Risk Statements: H226-H302-H315-H319-H335
• Safety Statements: P210-P233-P240-P241-P242-P243-P261-P264-P264+P265-P270-P271-P280-P301+P317-P302+P352-P303+P361+P353-P304+P340-P305+P351+P338-P319-P321-P330-P332+P317-P337+P317-P362+P364-P370+P378-P403+P233-P403+P235-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Flammable liquids	Flam. Liq.	3	H226
Acute toxicity	Acute Tox.	4	H302
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319
Eye irritation	Eye Irrit.	2A	H319

• Transport Information: UN 1224

Discovery and Applications

5-Chloro-2-pentanone is a versatile chemical compound with a chloro-ketone structure that has found applications in various fields, particularly in organic synthesis. This compound features a five-carbon chain with a chlorine atom attached at the second position and a ketone functional group at the fifth position. The synthesis and discovery of 5-chloro-2-pentanone stem from the broader exploration of halogenated ketones, which are valuable intermediates in organic chemistry due to their reactivity.

The discovery of 5-chloro-2-pentanone was part of the development of chloro-ketones in the mid-20th century, during a time when chemists were actively investigating halogenated organic compounds for their potential in diverse chemical reactions. The introduction of a chlorine atom into a ketone molecule provided a new dimension of reactivity, allowing for the creation of a variety of derivatives. Halogenated ketones, like 5-chloro-2-pentanone, became important reagents in organic synthesis because of their ability to undergo nucleophilic substitution reactions and to act as electrophiles in different chemical processes.

5-Chloro-2-pentanone is primarily utilized as an intermediate in organic synthesis, where it serves as a building block for more complex chemical structures. Its reactivity is largely due to the presence of both the chlorine atom, which is susceptible to nucleophilic attack, and the ketone group, which can participate in a range of reactions such as aldol condensations and reductions. This dual functionality makes 5-chloro-2-pentanone a useful reagent in the preparation of pharmaceuticals, agrochemicals, and fine chemicals.

In the pharmaceutical industry, 5-chloro-2-pentanone has been employed as a precursor in the synthesis of biologically active compounds. Its ability to form carbon-carbon bonds through nucleophilic substitution makes it a key intermediate in the development of complex drug molecules. Additionally, its chloro-ketone structure can be modified to introduce different functional groups, further enhancing its versatility in medicinal chemistry.

In agrochemical applications, 5-chloro-2-pentanone has been used in the synthesis of herbicides and pesticides. Its chemical properties allow it to serve as a starting material for the production of compounds that can inhibit the growth of unwanted plants or pests. The ability to modify its structure through substitution reactions enables the creation of specific molecules with targeted biological activity, making it valuable in the development of agricultural products.

The reactivity of 5-chloro-2-pentanone has also been exploited in the preparation of various functionalized organic molecules. It can undergo substitution reactions with nucleophiles such as amines, alcohols, or thiols to form corresponding derivatives. These reactions are useful in the synthesis of heterocyclic compounds, which are important in both the pharmaceutical and materials science fields.

Despite its broad utility, 5-chloro-2-pentanone must be handled with care due to its reactivity and potential hazards. As with many halogenated compounds, it can be corrosive and irritating to the skin, eyes, and respiratory system. Proper safety precautions, such as the use of personal protective equipment and proper ventilation, are necessary when working with this compound.

Overall, 5-chloro-2-pentanone is a valuable chemical intermediate with diverse applications in organic synthesis. Its reactivity makes it a key component in the development of pharmaceuticals, agrochemicals, and other fine chemicals. The compound’s chloro-ketone structure enables its use in a wide range of reactions, solidifying its place as an important reagent in modern organic chemistry.

References

2020. Methods of Synthesis of Remdesivir, Favipiravir, Hydroxychloroquine, and Chloroquine: Four Small Molecules Repurposed for Clinical Trials during the Covid-19 Pandemic. Synthesis.
DOI: 10.1055/s-0040-1707386

2018. Synthesis of 1-Aza-6,7-dehydrotropanes via Copper(I)-Catalyzed Coupling of 5-Chloropentan-2-one with Hydrazines and Terminal Alkynes. Synlett.
DOI: 10.1055/s-0037-1611041

2016. From a Pyridylhydrazine and a γ-Halo Ketone (Grandberg Synthesis). Science of Synthesis.
URL: https://science-of-synthesis.thieme.com/app/text/?id=SD-110-00728