1-Chloropentane
[CAS# 543-59-9]

Identification

• Classification: Chemical reagent >> Organic reagent >> Halogenated aliphatic hydrocarbon
• Name: 1-Chloropentane
• Synonyms: n-Amyl chloride; Pentyl chloride
• Molecular Formula: C₅H₁₁Cl
• Molecular Weight: 106.59
• CAS Registry Number: 543-59-9
• EC Number: 208-846-4
• SMILES: CCCCCCl

Properties

• Density: 0.9±0.1 g/cm³ Calc.^*, 0.881 g/mL (Expl.)
• Melting point: -99 °C (Expl.)
• Boiling point: 107.2±3.0 °C 760 mmHg (Calc.)^*, 107 - 108 °C (Expl.)
• Flash point: 11.1 °C (Calc.)^*, 3 °C (Expl.)
• Solubility: water practically insoluble (Expl.)
• Index of refraction: 1.406 (Calc.)^*, 1.412 (Expl.)

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

Safety Data

• Hazard Symbols: GHS02;GHS07 Danger
• Risk Statements: H225-H302-H312-H332
• Safety Statements: P210-P233-P240-P241-P242-P243-P261-P264-P270-P271-P280-P301+P317-P302+P352-P303+P361+P353-P304+P340-P317-P321-P330-P362+P364-P370+P378-P403+P235-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H312
Flammable liquids	Flam. Liq.	2	H225
Acute toxicity	Acute Tox.	4	H302

• Transport Information: UN 1107

Discovery and Applications

1-Chloropentane, also known as n-pentyl chloride, is a straight-chain primary alkyl halide with the molecular formula C₅H₁₁Cl. It is a colorless, flammable liquid with a characteristic odor and serves primarily as an intermediate in organic synthesis. Structurally, the chlorine atom is attached to the terminal carbon of a five-carbon linear chain, which imparts typical primary alkyl halide reactivity, favoring nucleophilic substitution reactions while being less prone to elimination under mild conditions.

The synthesis of 1-chloropentane is commonly achieved via the reaction of n-pentanol with hydrogen chloride or thionyl chloride. In this substitution reaction, the hydroxyl group is replaced by a chlorine atom, providing a straightforward method to produce the primary alkyl halide in high yield. Industrial production often involves careful control of reaction conditions such as temperature and solvent to minimize side reactions like dehydration, which could generate pentene isomers. The compound’s handling requires caution due to its flammability and potential irritant properties.

In organic synthesis, 1-chloropentane is a versatile building block used in nucleophilic substitution reactions, particularly S_N2 mechanisms, because the primary carbon allows for efficient attack by a variety of nucleophiles. Reactions with alcohols, amines, thiols, or cyanides yield ethers, amines, thioethers, and nitriles, respectively. These derivatives are valuable intermediates in the synthesis of pharmaceuticals, agrochemicals, and specialty chemicals, making 1-chloropentane an important reagent for the construction of more complex molecules.

Industrial applications of 1-chloropentane include its use in the preparation of plasticizers, lubricants, and surfactants. For example, the formation of alkylated esters from 1-chloropentane can yield compounds that modify viscosity, solubility, or hydrophobicity in formulations used in coatings, plastics, and personal care products. Its role as a precursor in the synthesis of higher molecular weight compounds is particularly valuable in processes that require controlled linear alkyl chains.

In the pharmaceutical industry, 1-chloropentane is used to introduce pentyl groups into bioactive molecules, influencing lipophilicity and metabolic properties. These modifications can improve drug solubility, membrane permeability, and pharmacokinetic profiles. Similarly, in agrochemical synthesis, it serves as an intermediate for herbicides, insecticides, and fungicides, contributing to the chemical specificity and stability of the active compounds.

Mechanistic studies of 1-chloropentane provide insight into S_N2 reaction kinetics and the effect of linear primary halides on nucleophilic substitution. Its simple structure allows chemists to explore reaction conditions, solvent effects, and nucleophile strength, which can inform the optimization of synthetic routes in both laboratory and industrial settings. The compound’s relatively low boiling point and volatility also facilitate purification through distillation.

Physically, 1-chloropentane is slightly soluble in water but miscible with organic solvents such as ethers, alcohols, and hydrocarbons. It is highly flammable, and safety precautions are necessary to prevent inhalation, skin contact, or eye exposure. Proper storage, ventilation, and use of personal protective equipment are essential. Environmental management focuses on preventing release into water and soil due to potential hazards associated with halogenated hydrocarbons.

The discovery and utilization of 1-chloropentane highlight its importance as a primary straight-chain alkyl halide. Its reactivity in nucleophilic substitution, role as a chemical intermediate, and broad applications in pharmaceuticals, agrochemicals, and industrial products demonstrate its continued relevance in modern chemical synthesis and industrial processes.

References

2019. Organosodium compounds for catalytic cross-coupling. Nature Catalysis, 2(3).
DOI: 10.1038/s41929-019-0250-6

2017. Viscosity of 1-chloropentane. Viscosity of Pure Organic Liquids and Binary Liquid Mixtures.
DOI: 10.1007/978-3-662-49218-5_156

2018. Chlorinating Reagents. Science of Synthesis.
URL: https://science-of-synthesis.thieme.com/app/text/?id=SD-228-00160