5-Chloro-2-ethylpyridine: Handling, Storage & Application Protocol

5-Chloro-2-ethylpyridine is a chlorinated pyridine building block widely employed as a versatile intermediate in heterocyclic synthesis and pharmaceutical research.

CAS Number

Not specified — see product page (SKU C729561)

Molecular Formula

C7H8ClN

Molecular Weight

141.60 g/mol

Recommended Storage

Cool, dry, well-ventilated area; away from incompatible materials (oxidizers, strong bases)

Appearance

Colorless to pale yellow liquid or solid (verify with CoA)

Primary Application

Intermediate in synthesis of pyridine-based pharmaceuticals, agrochemicals, and fine chemicals

Reagent Overview and Properties

5-Chloro-2-ethylpyridine (Aladdin SKU: C729561) is a halogenated pyridine derivative bearing an ethyl substituent at the 2-position and a chloro substituent at the 5-position of the pyridine ring. Its molecular formula is C₇H₈ClN, giving a molecular weight of approximately 141.60 g/mol.

The compound belongs to the class of chloropyridines, which are important electrophilic or nucleophilic building blocks in medicinal chemistry and process chemistry. The C–Cl bond at the 5-position is amenable to transition-metal-catalysed cross-coupling reactions (e.g., Suzuki, Negishi, Buchwald–Hartwig), nucleophilic aromatic substitution, and metal–halogen exchange, making 5-Chloro-2-ethylpyridine a versatile synthetic intermediate. The ethyl group at the 2-position can also provide a handle for directed C–H functionalisation under appropriate conditions.

Note: Confirm exact purity, appearance, and physical constants (melting/boiling point, refractive index) against the Certificate of Analysis (CoA) supplied with each lot before use.

Safety and Handling Requirements

Before working with 5-Chloro-2-ethylpyridine, consult the Safety Data Sheet (SDS) for the current lot. General precautions applicable to chlorinated pyridine reagents are outlined below.

• Personal Protective Equipment (PPE): Wear chemical-splash goggles, a lab coat, and nitrile gloves (minimum). Consider a half-face respirator if working outside a fume hood or with larger quantities.
• Ventilation: All weighing, transfer, and reaction operations must be performed inside a functioning chemical fume hood to minimise inhalation exposure.
• Skin and Eye Contact: In the event of skin contact, wash thoroughly with soap and water for at least 15 minutes. For eye contact, flush immediately with copious water for at least 15 minutes and seek medical attention.
• Incompatibilities: Keep away from strong oxidising agents, strong acids, strong bases, and reactive metals. Do not heat to decomposition.
• Waste Disposal: Dispose of waste in accordance with local, national, and institutional regulations for halogenated organic solvents and intermediates.

Review flag: Specific GHS hazard classifications (H-statements, P-statements) must be verified from the current Aladdin SDS for SKU C729561 before inclusion in any safety communication.

Storage Protocol

Proper storage preserves reagent purity and extends shelf life. Follow the guidelines below for 5-Chloro-2-ethylpyridine (C729561):

1. Temperature: Store at room temperature (15–25 °C) in a cool, dry location unless the CoA specifies refrigeration. Avoid prolonged exposure to heat or direct sunlight.
2. Container integrity: Keep the original, tightly sealed container. Re-seal immediately after each use with an inert gas (nitrogen or argon) blanket if the compound is moisture- or air-sensitive (verify with SDS/CoA).
3. Segregation: Store away from oxidisers, bases, and food/feed items. Use a dedicated cabinet for halogenated organics where available.
4. Labelling: Ensure the container is clearly labelled with the compound name, CAS number, lot number, date received, and date first opened.
5. Inventory checks: Inspect the reagent periodically for discolouration, precipitation, or odour changes that may indicate degradation; re-test purity if in doubt.

Review flag: Specific recommended storage temperature and shelf-life data must be confirmed from the Aladdin product page and CoA for lot-specific conditions.

Typical Synthetic Applications and Reaction Protocol

5-Chloro-2-ethylpyridine serves as an electrophilic heteroaromatic building block. The following general protocol outlines a representative transition-metal-catalysed cross-coupling application. Adapt conditions to the specific target molecule and coupling partner.

General Suzuki–Miyaura Cross-Coupling (Representative)

1. Reagent setup: Charge a dry, nitrogen-purged round-bottom flask with 5-Chloro-2-ethylpyridine (1.0 equiv), the desired aryl or heteroaryl boronic acid or ester (1.1–1.5 equiv), and a palladium catalyst (e.g., Pd(PPh₃)₄ or Pd(dppf)Cl₂, 1–5 mol%).
2. Base and solvent: Add an inorganic base (e.g., K₂CO₃ or Cs₂CO₃, 2–3 equiv) dissolved in a mixed solvent system (e.g., dioxane/water or DMF/water, 4:1 v/v).
3. Reaction: Stir the mixture at 80–110 °C under nitrogen for 12–24 hours. Monitor conversion by TLC or LCMS.
4. Work-up: Cool to room temperature, dilute with ethyl acetate, wash with saturated NH₄Cl solution and brine, dry over MgSO₄, filter, and concentrate under reduced pressure.
5. Purification: Purify the crude product by column chromatography (silica gel, appropriate eluent system).

Note: Reaction conditions (catalyst loading, temperature, time, solvent, base) must be optimised for each specific coupling partner and target. These conditions are indicative only. Refer to primary literature for validated procedures.

Review flag: No specific published yield or reaction data for C729561 were identified in the source material; all conditions above are textbook-level recommendations for chloropyridine Suzuki couplings and require experimental validation.

Quality Control and Troubleshooting

Maintaining reagent quality and diagnosing reaction problems are critical for reproducible results when using 5-Chloro-2-ethylpyridine.

Quality Control Checks

• Purity verification: Confirm purity by GC, HPLC, or NMR as appropriate before use in critical steps. Compare with the CoA specification for the lot.
• Identity confirmation: Use ¹H NMR and/or GC-MS to confirm compound identity. Key NMR signals include aromatic protons characteristic of a 2,5-disubstituted pyridine and the ethyl group quartet and triplet.
• Moisture content: If reactions are sensitive to moisture, determine water content by Karl Fischer titration.

Common Troubleshooting Points

• Low coupling yield: May indicate catalyst deactivation, insufficient base, or moisture ingress. Ensure rigorous anhydrous and anaerobic conditions for palladium-catalysed steps.
• Side products: Homocoupling or proto-dechlorination by-products can form if the catalyst loading is too high or if the base/temperature is not optimised.
• Reagent degradation: Discolouration or off-odour of the starting material may indicate partial decomposition; re-assay purity before use.

Review flag: Specific NMR chemical shift values and GC purity specifications for C729561 are not provided in the source material and must be confirmed from the Aladdin CoA.

Frequently asked questions

What is 5-Chloro-2-ethylpyridine used for in organic synthesis?

5-Chloro-2-ethylpyridine is primarily used as a heteroaromatic building block and intermediate. The C–Cl bond at the 5-position enables transition-metal-catalysed cross-coupling reactions (e.g., Suzuki, Negishi), nucleophilic aromatic substitution, and metal–halogen exchange, facilitating the construction of complex pyridine-containing scaffolds relevant to pharmaceutical and agrochemical research.

How should 5-Chloro-2-ethylpyridine (C729561) be stored?

Store in the original tightly sealed container in a cool, dry, well-ventilated location away from oxidisers, strong acids, and strong bases. Confirm lot-specific storage temperature recommendations from the Certificate of Analysis or the Aladdin product page. After opening, re-seal under an inert gas atmosphere if the compound is moisture- or air-sensitive.

What palladium catalysts are compatible with 5-Chloro-2-ethylpyridine in Suzuki coupling?

Commonly used palladium catalysts for Suzuki–Miyaura coupling of chloropyridines include Pd(PPh3)4, Pd(dppf)Cl2, and Pd(OAc)2 with appropriate phosphine ligands. The choice of catalyst and ligand should be optimised experimentally for the specific coupling partner. Bulky, electron-rich phosphine ligands are generally preferred for less reactive aryl chlorides.

How can I verify the purity of 5-Chloro-2-ethylpyridine before use?

Purity can be assessed by GC (gas chromatography) or HPLC and cross-referenced with the lot Certificate of Analysis provided by Aladdin. Identity confirmation can be performed by 1H NMR, which should show signals consistent with a 2,5-disubstituted pyridine ring and an ethyl substituent. If the reagent shows discolouration or unusual odour, re-test before use in critical reactions.

References

1. Aladdin Scientific. 5-Chloro-2-ethylpyridine, SKU C729561. Product page and Certificate of Analysis.
2. Miyaura N, Suzuki A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem Rev. 1995;95(7):2457–2483. doi:10.1021/cr00039a007
3. Johansson Seechurn CCC, Kitching MO, Colacot TJ, Snieckus V. Palladium-Catalyzed Cross-Coupling: A Historical Contextual Perspective to the 2010 Nobel Prize. Angew Chem Int Ed. 2012;51(21):5062–5085. doi:10.1002/anie.201107017

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.