L-1-Phenylethylamine
[CAS 2627-86-3]

Identification

• Classification: Analytical chemistry >> Analytical reagent >> Common analytical reagents
• Name: L-1-Phenylethylamine
• Synonyms: (S)-(-)-1-Phenylethylamine; L(-)-alpha-Methylbenzylamine; (-)-PEA
• Molecular Formula: C₈H₁₁N
• Molecular Weight: 121.18
• CAS Registry Number: 2627-86-3
• EC Number: 220-098-0
• SMILES: C[C@@H](C1=CC=CC=C1)N

Properties

• Water solubility: slightly soluble
• Density: 1.0±0.1 g/cm³ Calc.^*, 0.948 g/mL (Expl.)
• Melting point: -10 °C (Expl.)
• Boiling point: 183.0±9.0 °C 760 mmHg (Calc.)^*, 187 °C (Expl.)
• Flash point: 79.4 °C (Calc.)^*, 71 °C (Expl.)
• Index of refraction: 1.533 (Calc.)^*, 1.526 (Expl.)

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

Safety Data

• Hazard Symbols: GHS05;GHS07 Danger
• Risk Statements: H302+H312-H302-H312-H314-H318-H319
• Safety Statements: P260-P264-P264+P265-P270-P280-P301+P317-P301+P330+P331-P302+P352-P302+P361+P354-P304+P340-P305+P351+P338-P305+P354+P338-P316-P317-P321-P330-P337+P317-P362+P364-P363-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H312
Skin corrosion	Skin Corr.	1C	H314
Eye irritation	Eye Irrit.	2	H319
Skin corrosion	Skin Corr.	1B	H314
Serious eye damage	Eye Dam.	1	H318
Acute toxicity	Acute Tox.	3	H311
Acute toxicity	Acute Tox.	3	H331
Acute toxicity	Acute Tox.	3	H301
Flammable liquids	Flam. Liq.	4	H227

• Transport Information: UN 2735

Discovery and Applications

L-1-Phenylethylamine, also known as (S)-1-phenylethylamine, is a chiral aromatic amine with the molecular framework C₆H₅–CH(CH₃)–NH₂. It consists of a phenyl ring attached to an ethylamine backbone and contains a stereogenic carbon atom, giving rise to two enantiomeric forms: the L/(S) form and the D/(R) form. The L designation refers to a specific stereochemical configuration and does not necessarily correspond universally to optical rotation signs across naming systems.

Structurally, L-1-phenylethylamine belongs to the class of primary amines and can be viewed as a substituted analogue of ethylamine in which one hydrogen atom is replaced by a phenyl group. The amino group contributes basicity and nucleophilicity, while the aromatic ring provides hydrophobic character and opportunities for π-interactions.

The stereochemistry of this molecule is particularly important because the two enantiomers often display different chemical and biological behavior. Chiral amines such as L-1-phenylethylamine are widely used in asymmetric synthesis, where they function as chiral auxiliaries, resolving agents, or intermediates for preparing enantiomerically enriched compounds. Their ability to distinguish between different spatial arrangements of molecules makes them valuable in stereoselective chemistry.

The amino group readily undergoes protonation under acidic conditions to form ammonium salts, which generally exhibit improved aqueous solubility. It can also participate in common amine reactions including:

* Acylation to form amides
* Alkylation to generate secondary or tertiary amines
* Condensation with carbonyl compounds to form imines or related derivatives
* Formation of Schiff bases and chiral ligands

The phenyl ring influences the molecule electronically and sterically. Although the aromatic ring itself is relatively stable, it can undergo electrophilic aromatic substitution reactions under suitable conditions. The benzylic carbon adjacent to the ring also exhibits characteristic reactivity because benzylic intermediates can be stabilized by resonance.

From a physicochemical perspective, L-1-phenylethylamine exhibits mixed hydrophilic and lipophilic characteristics. The aromatic ring contributes hydrophobicity, whereas the amine group increases polarity and hydrogen-bonding capability. As a free base it is more soluble in organic solvents, while protonated salt forms generally show increased water solubility.

L-1-Phenylethylamine is widely used as a synthetic intermediate in pharmaceutical chemistry, fine chemical production, and chiral synthesis. Enantiomerically pure phenylethylamines are particularly valuable because many biologically active molecules exhibit stereochemistry-dependent activity.

Overall, L-1-phenylethylamine is a chiral primary aromatic amine whose significance lies in its stereochemical properties, synthetic versatility, and broad use as a building block in asymmetric and medicinal chemistry.

References

2025. Biocatalysis in medicinal chemistry: sustainable enzymatic transformations for drug synthesis. Discover Chemistry.
DOI: 10.1007/s44371-025-00376-9

2025. Characterization and substrate specificity study of the novel (R)-amine transaminase MagAT. Biotechnology Letters.
DOI: 10.1007/s10529-025-03672-7

2025. Functional and structural insights into a thermostable (S)-selective amine transaminase and its improved substrate scope by protein engineering. Applied Microbiology and Biotechnology.
DOI: 10.1007/s00253-025-13536-9