5-[(2-Hydroxyethyl)amino]-o-cresol
[CAS# 55302-96-0]

Identification

• Name: 5-[(2-Hydroxyethyl)amino]-o-cresol
• Synonyms: 2-Methyl-5-(hydroxyethyl)aminophenol; 2-Methyl-5-N-hydroxyethylamino phenol
• Molecular Formula: C₉H₁₃NO₂
• Molecular Weight: 167.21
• CAS Registry Number: 55302-96-0
• EC Number: 259-583-7
• SMILES: CC1=C(C=C(C=C1)NCCO)O

Properties

• Density: 1.2±0.1 g/cm³ Calc.^*
• Boiling point: 366.0±32.0 °C 760 mmHg (Calc.)^*
• Flash point: 181.4±15.7 °C (Calc.)^*
• Index of refraction: 1.626 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS07;GHS09 Warning
• Risk Statements: H315-H319-H335-H411
• Safety Statements: P261-P264-P264+P265-P271-P273-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P391-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Specific target organ toxicity - single exposure	STOT SE	3	H335
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H302

Discovery and Applications

5-[(2-Hydroxyethyl)amino]-o-cresol is an aromatic compound characterized by a benzene ring substituted with three key functional groups: a hydroxyl group (–OH) at the ortho position relative to the amino substituent, a methyl group (–CH₃) at the adjacent position, and a 2-hydroxyethylamino substituent attached at the 5-position. Its molecular formula is C₉H₁₃NO₂. The presence of both hydroxyl and amino groups, along with the hydroxyethyl side chain, gives the molecule distinct physicochemical and reactive properties.

This compound can be regarded as a derivative of o-cresol, where the amino group is further substituted by a 2-hydroxyethyl moiety. The synthesis of 5-[(2-hydroxyethyl)amino]-o-cresol typically involves the reaction of 5-amino-o-cresol with ethylene oxide or related 2-haloethyl compounds under controlled conditions, leading to nucleophilic substitution and formation of the hydroxyethylamine side chain. Alternative synthetic routes may include reductive amination or other alkylation methods targeting the amino group.

The compound is primarily used as an intermediate in the production of hair dye formulations. Its structure enables it to function as a dye precursor or coupling agent in oxidative hair color processes. The amino and hydroxyethyl groups participate in oxidation and coupling reactions, often in the presence of oxidants like hydrogen peroxide, forming chromophores that impart color to hair fibers. The methyl and hydroxyl groups on the aromatic ring influence electron distribution and steric factors, affecting the shade and intensity of the color produced.

Besides hair dye applications, 5-[(2-hydroxyethyl)amino]-o-cresol serves as a building block in organic synthesis, where its functional groups can be exploited to create heterocyclic compounds or modified derivatives with potential pharmaceutical or agrochemical activity. The hydroxyethyl substituent offers sites for further chemical modification, such as esterification or etherification, expanding its versatility.

The compound’s physicochemical properties include moderate solubility in water and polar organic solvents, attributable to the balance between hydrophobic aromatic and hydrophilic hydroxyl and amino groups. Analytical methods used to characterize 5-[(2-hydroxyethyl)amino]-o-cresol include nuclear magnetic resonance (NMR) spectroscopy, which elucidates its structural features and confirms substitution patterns. Infrared (IR) spectroscopy identifies characteristic functional group absorptions, including those from hydroxyl, amino, and aromatic moieties. Chromatographic techniques such as high-performance liquid chromatography (HPLC) are employed to assess purity and monitor synthesis progress.

From a safety perspective, the compound should be handled with care, as aromatic amines and related derivatives may cause skin irritation or sensitization in some individuals. Appropriate personal protective equipment such as gloves and eye protection should be used during handling. Its use in cosmetic products is regulated to ensure safety for consumers, with formulations tested for adverse effects before market approval.

In summary, 5-[(2-hydroxyethyl)amino]-o-cresol is a functionally diverse aromatic compound utilized mainly as a hair dye intermediate. Its combination of amino, hydroxyethyl, methyl, and hydroxyl substituents confer unique chemical reactivity, facilitating its role in oxidative dye chemistry and organic synthesis. Established synthetic methods, characterization techniques, and safety considerations support its application in cosmetic and chemical industries.

References

2020. Springer Lexikon Kosmetik und Körperpflege. Springer Lexikon Kosmetik und Körperpflege.
DOI: 10.1007/978-3-662-59127-7_13

2016. Hair Dyes. Quick Guide to Contact Dermatitis.
DOI: 10.1007/978-3-662-47714-4_16

2009. Metabolite screening of aromatic amine hair dyes using in vitro hepatic models. Xenobiotica; the fate of foreign compounds in biological systems, 39(10).
DOI: 10.1080/00498250903134443