1-Chloropentane: Properties, Uses & Handling FAQs

1-Chloropentane is a short-chain primary alkyl chloride widely used as a synthetic intermediate and solvent in organic chemistry research.

CAS Number

543-59-9

Molecular Formula

C₅H₁₁Cl

Molecular Weight

106.59 g/mol

Boiling Point

108–109 °C at 760 mmHg

Appearance

Colorless liquid

Synonyms

n-Pentyl chloride; Amyl chloride

What Is 1-Chloropentane?

1-Chloropentane (CAS 543-59-9), also known as n-pentyl chloride or amyl chloride, is a primary alkyl halide with the molecular formula C₅H₁₁Cl and a molecular weight of 106.59 g/mol. It consists of a five-carbon straight-chain alkyl group bearing a chlorine atom at the terminal (C-1) position. At room temperature it is a colorless, mobile liquid with a characteristic ether-like odor. Its primary alkyl nature makes it a reactive yet selective electrophilic partner in a variety of organic transformations.

Physical and Chemical Properties

1-Chloropentane is a hydrophobic liquid that is miscible with common organic solvents such as diethyl ether, dichloromethane, hexane, and acetone, but is essentially immiscible with water. Key physical properties include a boiling point of approximately 108–109 °C at atmospheric pressure, a density of roughly 0.88 g/mL at 20 °C, and a refractive index near 1.412. The C–Cl bond is polarized, rendering the carbon electrophilic and susceptible to nucleophilic attack. As a primary substrate, 1-chloropentane undergoes predominantly S_N2 reactions with strong nucleophiles (e.g., NaI in acetone, NaOH, NaCN, organolithium reagents) and E2 elimination under strongly basic conditions. It is flammable, with a flash point in the range of approximately 13 °C (closed cup), requiring appropriate fire-safety precautions in the laboratory.

Laboratory Applications and Uses

In synthetic organic chemistry, 1-chloropentane serves several important roles:

• Alkylation reagent: It introduces an n-pentyl chain onto nucleophiles such as amines, thiols, alcohols (via Williamson synthesis), and stabilized carbanions.
• Grignard precursor: Reaction with magnesium turnings in anhydrous diethyl ether or THF yields pentylmagnesium chloride, a versatile carbon nucleophile for addition to carbonyl compounds.
• Finkelstein reactions: Exchange of the chloride with iodide (NaI/acetone) produces 1-iodopentane, enabling access to more reactive alkyl iodide intermediates.
• Model substrate: Widely used in teaching and research laboratories to demonstrate and study S_N2 kinetics, E2 selectivity, and structure–reactivity relationships in aliphatic nucleophilic substitution.
• Specialty solvent: Its moderate boiling point and lipophilicity make it useful as a co-solvent or extraction medium in certain analytical and preparative procedures.

Safe Handling and Storage

1-Chloropentane is classified as a flammable liquid and an irritant. The following precautions are recommended:

• Personal protective equipment (PPE): Wear chemical-resistant gloves (e.g., nitrile or neoprene), safety goggles, and a lab coat. Work in a well-ventilated fume hood to avoid inhalation of vapors.
• Fire precautions: Keep away from open flames, sparks, and other ignition sources. Use explosion-proof electrical equipment. Have a CO₂ or dry-chemical extinguisher accessible.
• Storage: Store in a tightly sealed container in a cool (below 25 °C), dry, well-ventilated location away from oxidizers and ignition sources. Amber glass bottles are preferred to minimize photodegradation.
• Waste disposal: Dispose of as halogenated organic solvent waste in accordance with local, national, and institutional regulations.
• First aid: In case of skin contact, wash thoroughly with soap and water. In case of eye contact, irrigate immediately with copious water and seek medical attention. If inhaled, move the affected person to fresh air.

Always consult the current Safety Data Sheet (SDS) before use.

Purity, Grade, and Quality Specifications

For research applications, 1-chloropentane is typically available in reagent-grade purity of ≥97–99% by GC analysis. Common impurities include isomeric chloropentanes (e.g., 2-chloropentane), residual moisture, and trace hydrocarbons. When selecting a grade, consider:

• GC purity: For sensitive reactions such as Grignard formation or metal-mediated cross-coupling, high-purity (≥98% GC) material minimizes side reactions from isomeric or protic impurities.
• Water content: Anhydrous grades with low Karl Fischer water content are recommended for moisture-sensitive reactions.
• Inhibitor status: 1-Chloropentane does not typically require a radical inhibitor, but long-term storage may lead to trace HCl formation; freshly opened or recently tested material is preferred for critical applications.

Aladdin Scientific's 1-Chloropentane (SKU: C109473) is supplied with a certificate of analysis (CoA) specifying lot-specific purity data. Contact technical support for detailed specification sheets.

Frequently asked questions

What is the difference between 1-Chloropentane and 2-Chloropentane in terms of reactivity?

1-Chloropentane is a primary alkyl chloride and reacts preferentially via the Sₙ2 mechanism with strong nucleophiles, offering faster substitution rates and minimal steric hindrance. 2-Chloropentane is a secondary alkyl chloride that can undergo both Sₙ1 and Sₙ2 pathways depending on the nucleophile and solvent, and it is more prone to elimination side products. For clean alkylation of carbon or heteroatom nucleophiles, the primary substrate (1-chloropentane) is generally preferred.

How should I prepare pentylmagnesium chloride from 1-Chloropentane?

To prepare pentylmagnesium chloride, add 1-Chloropentane dropwise to activated magnesium turnings in anhydrous THF or diethyl ether under an inert atmosphere (N₂ or Ar). The reaction typically requires initiation by gentle warming or addition of a small crystal of iodine or a drop of 1,2-dibromoethane. Once initiated, maintain the addition rate to keep the reaction under gentle reflux. All glassware must be oven-dried and the solvent rigorously dried and degassed prior to use.

Can 1-Chloropentane be used as a solvent in organic reactions?

Yes, 1-Chloropentane can serve as a co-solvent or extraction medium in select procedures due to its moderate boiling point (108–109 °C) and low water miscibility. However, because it is itself a reactive alkyl halide electrophile, it is not suitable as an inert reaction solvent in reactions involving strong nucleophiles or bases, as it may alkylate the reactants. In such cases, genuinely inert solvents such as hexane, toluene, or THF are more appropriate.

What are the main hazards associated with 1-Chloropentane?

The primary hazards of 1-Chloropentane are flammability (flash point approximately 13 °C, classified as a flammable liquid) and irritation to skin, eyes, and respiratory mucous membranes upon contact or vapor inhalation. Prolonged or repeated skin exposure may cause defatting and dermatitis. It should always be handled in a fume hood, away from ignition sources, with appropriate PPE. Refer to the current SDS for full hazard classification and emergency response guidance.

How should 1-Chloropentane be stored to maintain its purity?

Store 1-Chloropentane in a tightly sealed amber glass container in a cool (below 25 °C), dry area away from light, heat, and ignition sources. Segregate from oxidizing agents and strong bases. Upon opening, minimise exposure to air and moisture to prevent trace hydrolysis to 1-pentanol and HCl formation. For long-term storage, consider purging the headspace with dry inert gas (N₂ or Ar) before resealing.

References

1. March, J. Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 4th ed.; Wiley-Interscience: New York, 1992.
2. Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed.; Oxford University Press: Oxford, 2012.
3. National Institute of Standards and Technology (NIST). 1-Chloropentane. NIST WebBook, SRD 69. https://webbook.nist.gov/
4. Aladdin Scientific. Certificate of Analysis, 1-Chloropentane, SKU C109473. Aladdin Scientific Corp.

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