4-Dimethylaminobenzoic acid
[CAS# 619-84-1]

Identification

• Classification: Biochemical >> Amino acids and their derivatives >> Other amino acid derivatives
• Name: 4-Dimethylaminobenzoic acid
• Synonyms: p-(N,N'-Dimethylamino) benzoic acid
• Molecular Formula: C₉H₁₁NO₂
• Molecular Weight: 165.19
• Protein Sequence: X
• CAS Registry Number: 619-84-1
• EC Number: 210-615-8
• SMILES: CN(C)C1=CC=C(C=C1)C(=O)O

Properties

• Density: 1.2±0.1 g/cm³ Calc.^*
• Melting point: 241 - 243 °C (Decomposes) (Expl.)
• Boiling point: 315.8±25.0 °C 760 mmHg (Calc.)^*
• Flash point: 144.8±23.2 °C (Calc.)^*, 170 °C (Expl.)
• Index of refraction: 1.594 (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

Discovery and Applications

4-Dimethylaminobenzoic acid is an aromatic carboxylic acid compound with the molecular formula C₉H₁₁NO₂. It consists of a benzoic acid core substituted at the para (4-) position with a dimethylamino group (–N(CH₃)₂). This structural arrangement gives the compound both acidic (carboxylic acid) and basic (amine) functional properties, and it is commonly used in organic synthesis, pharmaceutical development, and analytical chemistry.

The compound is a derivative of benzoic acid and was first synthesized during early 20th-century investigations into substituted aromatic acids and amines. It is typically prepared by dimethylation of 4-aminobenzoic acid using methylating agents such as dimethyl sulfate or methyl iodide under basic conditions.

4-Dimethylaminobenzoic acid has been used in various synthetic pathways as a starting material or intermediate. The electron-donating nature of the dimethylamino group influences the reactivity of the aromatic ring, making it more reactive toward electrophilic substitution and useful in the formation of dyes, pH indicators, and functionalized materials. In particular, it is a known intermediate in the synthesis of azo dyes and fluorescent compounds, where its electron-rich structure enhances chromophore behavior.

In pharmaceutical chemistry, derivatives of 4-dimethylaminobenzoic acid have been explored for their bioactivity and drug-like properties. Some esters of this compound, such as its ethyl ester, are used as UV absorbers in sunscreen formulations and as excipients in topical medications. Related compounds have also been studied for local anesthetic activity, based on their structural similarity to para-aminobenzoic acid (PABA), a known pharmacophore in anesthetic agents.

The compound has also served a role in analytical chemistry, particularly in spectrophotometric and chromatographic methods. Its conjugated aromatic system and the auxochromic dimethylamino group contribute to its UV-visible absorbance properties, which are useful for detection and quantification in chemical assays.

4-Dimethylaminobenzoic acid is a solid at room temperature, typically appearing as a light yellow crystalline powder. It is sparingly soluble in water but more soluble in alcohols and organic solvents like ethanol or acetone. It has a melting point in the range of 170–175 °C. The carboxylic acid group can be readily converted into salts, esters, or amides, allowing for further modification and incorporation into complex molecules.

Safety data indicate that the compound should be handled with care. Although it has relatively low acute toxicity, it may cause irritation to the skin, eyes, or respiratory tract upon direct exposure. Proper laboratory safety practices, including gloves and eye protection, are recommended during use.

In summary, 4-dimethylaminobenzoic acid is a synthetically useful aromatic acid known for its role in dye chemistry, UV-absorbing agents, and pharmaceutical intermediates. Its electron-rich, dual-functional structure allows it to participate in diverse chemical transformations relevant to industrial and academic research.

References

2017. Studies on the formation of formaldehyde during 2-ethylhexyl 4-(dimethylamino)benzoate demethylation in the presence of reactive oxygen and chlorine species. Environmental science and pollution research international, 24(10).
DOI: 10.1007/s11356-017-8477-8

2014. Evaluation of benzoic acid derivatives as sirtuin inhibitors. Bioorganic & Medicinal Chemistry Letters, 24(1).
DOI: 10.1016/j.bmcl.2013.11.004

1981. Slow-acting Amine Polymerization Accelerators. Para-dimethylaminobenzoic Acid and Its Ethyl Ester. Journal of Dental Research, 60(7).
DOI: 10.1177/00220345810600070701