2-Ethylpyridine
[CAS# 100-71-0]

Identification

• Classification: Pharmaceutical intermediate >> Heterocyclic compound intermediate >> Pyridine compound >> Ethylpyridine
• Name: 2-Ethylpyridine
• Molecular Formula: C₇H₉N
• Molecular Weight: 107.15
• CAS Registry Number: 100-71-0
• EC Number: 202-881-9
• SMILES: CCC1=CC=CC=N1

Properties

• Density: 0.9±0.1 g/cm³ Calc.^*, 0.937 g/mL (Expl.)
• Melting point: -63 ºC (Expl.)
• Boiling point: 150.3±3.0 ºC 760 mmHg (Calc.)^*, 149 ºC (Expl.)
• Flash point: 29.4 ºC (Calc.)^*, 37 ºC (Expl.)
• Solubility: water: ~45 g/L (20 ºC) (Expl.)
• Index of refraction: 1.499 (Calc.)^*, 1.496 (Expl.)

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

Safety Data

• Hazard Symbols: GHS02;GHS07 WarningGHS02
• Hazard Statements: H226-H312+H332-H312-H315-H319-H332-H335
• Precautionary Statements: P210-P233-P240-P241-P242-P243-P261-P264-P264+P265-P271-P280-P302+P352-P303+P361+P353-P304+P340-P305+P351+P338-P317-P319-P321-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
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H302
Specific target organ toxicity - single exposure	STOT SE	2	H335
Reproductive toxicity	Repr.	2	H361
Eye irritation	Eye Irrit.	2A	H319
Specific target organ toxicity - repeated exposure	STOT RE	2	H373

• Transport Information: UN 1993

Discovory and Applicatios

2-Ethylpyridine is a substituted pyridine in which an ethyl group occupies the position adjacent to the ring nitrogen. It belongs to the broader family of alkylpyridines, a class of heteroaromatic compounds that have been studied extensively because of their occurrence in coal tar, their characteristic basicity, and their usefulness as intermediates in chemical synthesis. The compound is a colorless to pale yellow liquid with a strong, penetrating odor, reflecting the typical sensory properties of low-molecular-weight pyridine derivatives.

The discovery of 2-ethylpyridine is closely connected to the historical investigation of coal tar in the nineteenth and early twentieth centuries. During this period, chemists systematically separated and characterized nitrogen-containing bases obtained from coal tar distillation. Pyridine itself was identified first, followed by a variety of alkyl-substituted pyridines, including the ethylpyridines. Early studies established that 2-ethylpyridine could be isolated as a minor component of coal tar bases and distinguished from its positional isomers by differences in boiling point, salt formation, and reactivity. These investigations played an important role in understanding how alkyl substitution affects the electronic properties and steric environment of the pyridine ring.

As synthetic organic chemistry advanced, laboratory methods for preparing 2-ethylpyridine were developed, allowing the compound to be obtained in higher purity and larger quantities than was possible from coal tar isolation alone. Synthetic routes generally relied on ring-forming reactions or alkylation strategies starting from simpler nitrogen-containing precursors. Through such work, chemists confirmed the structure of 2-ethylpyridine and clarified how substitution at the 2-position influences basicity and coordination behavior compared with unsubstituted pyridine and other alkylpyridine isomers. These foundational studies established 2-ethylpyridine as a well-defined and reproducible chemical substance suitable for further application.

In terms of application, 2-ethylpyridine has been used primarily as an intermediate in organic synthesis. Its heteroaromatic ring and basic nitrogen atom make it a useful building block for the preparation of more complex molecules. In particular, it has served as a precursor in the synthesis of agrochemicals, pharmaceuticals, and specialty chemicals, where the pyridine motif is valued for its ability to modulate biological activity and physicochemical properties. Substitution at the 2-position can introduce steric effects that influence binding interactions in biologically active compounds, making 2-ethylpyridine-derived structures attractive in medicinal chemistry research.

Another important area of application is coordination and catalytic chemistry. Like pyridine, 2-ethylpyridine can act as a ligand toward transition metals, donating its lone pair of electrons on nitrogen to form coordination complexes. The presence of the ethyl substituent alters both the steric profile and the electron-donating properties of the ligand, which can affect metal–ligand bond strength and catalytic performance. As a result, 2-ethylpyridine and related alkylpyridines have been examined as modifiers or auxiliary ligands in homogeneous catalysis and organometallic chemistry.

2-Ethylpyridine has also found use as a solvent or additive in specific industrial and laboratory contexts. Its moderate basicity allows it to neutralize acidic byproducts or stabilize reactive intermediates in certain reactions. Additionally, alkylpyridines, including 2-ethylpyridine, have been studied for their roles in flavors and odors, particularly as contributors to roasted or smoky aromas, although such applications are generally indirect and rely on controlled formulation rather than the pure compound itself.

Overall, the history of 2-ethylpyridine reflects the broader development of heterocyclic chemistry, from early isolation from complex natural mixtures to deliberate synthesis and targeted application. Its continued use as a chemical intermediate and ligand underscores the enduring importance of simple substituted pyridines in both fundamental research and applied chemical industries.

References

Furst AF (1949) The reduction of 2-acetylpyridine to 2-ethylpyridine. Journal of the American Chemical Society 71(10) 3550–3551 DOI: 10.1021/ja01178a513

Malik M, Świtlicka A, Bieńko A, Komarnicka UK, Bieńko DC, Kozieł S, Kyzioł A, Mazur T, Machura B (2022) Copper(ii) complexes with 2-ethylpyridine and related hydroxyl pyridine derivatives: structural, spectroscopic, magnetic and anticancer in vitro studies. RSC Advances 12 27648–27665 DOI: 10.1039/D2RA05133H

Morais VMF, Miranda MS, Matos MAG (2003) Thermochemical study of the ethylpyridine and ethylpyrazine isomers. Organic & Biomolecular Chemistry (Issue 23) — DOI available on publisher site but search by title on RSC Publishing. DOI: 10.1039/B308097H