Methyl 4-aminobenzoate
[CAS 619-45-4]

Identification

• Classification: Biochemical >> Amino acids and their derivatives >> Ester amino acid
• Name: Methyl 4-aminobenzoate
• Synonyms: 4-Aminobenzoic acid methyl ester
• Molecular Formula: C₈H₉NO₂
• Molecular Weight: 151.16
• CAS Registry Number: 619-45-4
• EC Number: 210-598-7
• SMILES: COC(=O)C1=CC=C(C=C1)N

Properties

• Density: 1.2±0.1 g/cm³ Calc.^*
• Melting point: 110 - 111 °C (Expl.)
• Boiling point: 299.2±13.0 °C 760 mmHg (Calc.)^*
• Flash point: 154.9±17.4 °C (Calc.)^*
• Index of refraction: 1.566 (Calc.)^*

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

Safety Data

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

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319
Eye irritation	Eye Irrit.	2A	H319

chemBlink Chemical Story

Methyl 4-aminobenzoate, CAS 619-45-4, is the methyl ester of p-aminobenzoic acid (PABA). NIST and PubChem record the formula C8H9NO2 and molecular weight 151.16. The molecule carries two para-related functional groups on a benzene ring: an amino group that can act as a nucleophile and a methyl ester that can undergo the familiar chemistry of carboxylic-acid derivatives.

This combination makes methyl 4-aminobenzoate a useful synthetic intermediate. The amino group can be acylated, alkylated, diazotized or incorporated into ureas and other nitrogen-containing structures. The ester can be hydrolyzed back to the acid, transformed through nucleophilic acyl substitution, or retained as a protected carboxyl functionality while chemistry is performed at the amino group.

The para arrangement gives a relatively symmetric aromatic framework and electronically connects the electron-donating amino group with the electron-withdrawing ester across the ring. This donor-acceptor relationship influences ultraviolet absorption and makes p-aminobenzoate derivatives useful subjects in physical-organic and materials studies as well as routine synthesis.

PABA itself has a biological history as a component of folate biosynthesis in microorganisms and was once widely associated with sunscreen chemistry. The methyl ester should not automatically be assigned all uses or biological properties of PABA, however. Esterification changes acidity, polarity and metabolic behavior, and CAS 619-45-4 is a distinct chemical substance.

Public databases strongly document identity, spectra and crystal structure, but do not support one uniquely dominant industrial application for the methyl ester. Its most reliable role is therefore as a fine-chemical and research building block in which amino and ester chemistry can be manipulated independently.

References:
1. PubChem, Methyl 4-aminobenzoate, CID 12082, CAS 619-45-4.
2. NIST Chemistry WebBook, Benzoic acid, 4-amino-, methyl ester, CAS 619-45-4.
3. Joule JA, Mills K. Heterocyclic Chemistry. 5th ed. Wiley, 2010.

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