4-Acetylnaphthalene-1-carboxylic acid
[CAS# 131986-05-5]

Identification

• Classification: Pharmaceutical intermediate >> Heterocyclic compound intermediate >> Pyrimidine compound >> Carboxylic acid
• Name: 4-Acetylnaphthalene-1-carboxylic acid
• Molecular Formula: C₁₃H₁₀O₃
• Molecular Weight: 214.22
• CAS Registry Number: 131986-05-5
• EC Number: 807-884-4
• SMILES: CC(=O)C1=CC=C(C2=CC=CC=C21)C(=O)O

Properties

• Density: 1.3±0.1 g/cm³, Calc.^*
• Index of Refraction: 1.649, Calc.^*
• Boiling Point: 442.9±28.0 ºC (760 mmHg), Calc.^*
• Flash Point: 235.8±20.5 ºC, Calc.^*

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

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H319
• Precautionary Statements: P264+P265-P280-P305+P351+P338-P337+P317

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319

Discovory and Applicatios

4-Acetylnaphthalene-1-carboxylic acid is an aromatic organic compound with the molecular formula C₁₃H₁₀O₃. It consists of a naphthalene ring substituted at the 1-position with a carboxylic acid group (–COOH) and at the 4-position with an acetyl group (–COCH₃). This dual substitution on the polycyclic aromatic backbone imparts unique chemical properties that are useful in various synthetic and applied contexts.

The naphthalene ring is a fused system of two benzene rings, known for its planar structure and extended conjugation. The presence of electron-withdrawing substituents such as the carboxylic acid and acetyl groups modulates the reactivity of the aromatic core, directing electrophilic substitutions and enabling selective functionalization. The combination of these groups on adjacent rings of the naphthalene system makes 4-acetylnaphthalene-1-carboxylic acid a valuable intermediate in aromatic chemistry.

This compound can be synthesized through several well-established procedures. One classical route involves the Friedel–Crafts acylation of naphthalene derivatives, followed by oxidation. Specifically, 1-acetylnaphthalene can undergo controlled oxidation to introduce a carboxylic acid group at the 4-position. Alternatively, 1-carboxynaphthalene can be acylated using acetyl chloride in the presence of a Lewis acid such as aluminum chloride (AlCl₃), promoting substitution at the 4-position due to the directing effects of the carboxyl group.

4-Acetylnaphthalene-1-carboxylic acid is structurally rigid, and the proximity of the carbonyl groups in both the acetyl and carboxyl moieties may result in intramolecular hydrogen bonding, influencing its solubility and melting point. The compound is typically a crystalline solid and is sparingly soluble in water but readily dissolves in organic solvents like dimethyl sulfoxide (DMSO), acetone, and ethanol.

From a synthetic standpoint, the carboxylic acid group allows for further derivatization into esters, amides, or acid chlorides, which can be used in the preparation of dyes, functional polymers, and pharmaceuticals. The acetyl group may undergo typical reactions such as reduction to a hydroxymethyl group or condensation with hydrazines or amines to form various heterocycles. These transformations make the compound a useful intermediate for more complex aromatic and polycyclic compounds.

In materials chemistry, naphthalene derivatives such as this one are important in the development of optoelectronic materials, including organic light-emitting diodes (OLEDs) and liquid crystals. The electron-withdrawing groups affect the electronic distribution in the aromatic ring, which in turn influences the optical and electronic behavior of the molecule when incorporated into larger systems.

Spectroscopic techniques are used to characterize this compound. In ²H NMR spectroscopy, the aromatic protons of the naphthalene ring appear in the downfield region, while the methyl protons of the acetyl group appear as a singlet in the upfield region. The carboxylic acid proton typically resonates further downfield due to deshielding. In ³C NMR, characteristic signals are observed for the carbonyl carbons, aromatic carbons, and methyl group. Infrared (IR) spectroscopy shows strong absorption bands near 1700 cm⁻¹ for the carbonyl stretching of both the carboxylic acid and ketone groups, along with a broad O–H stretch above 3000 cm⁻¹.

In conclusion, 4-acetylnaphthalene-1-carboxylic acid is a structurally defined, functionally rich aromatic compound that serves as a key intermediate in synthetic organic chemistry. Its unique substitution pattern on the naphthalene ring supports further chemical modifications and provides useful electronic properties for applications in both fine chemicals and materials science.