For scientists, researchers, and procurement specialists in the chemical and pharmaceutical industries, a deep understanding of a compound's properties is fundamental to its effective utilization. This article provides a comprehensive overview of the chemical properties of 5-Bromo-4-methoxy-2-methylbenzoic acid (CAS: 875245-69-5), a critical intermediate known for its role in advanced organic synthesis and pharmaceutical development. Understanding these characteristics ensures optimal handling, storage, and application.

Molecular Structure and Physical Characteristics

5-Bromo-4-methoxy-2-methylbenzoic acid, with the molecular formula C9H9BrO3 and a molecular weight of approximately 245.07 g/mol, presents as a white powder. Its structure features a benzoic acid core substituted with a bromine atom at the 5-position, a methoxy group (-OCH3) at the 4-position, and a methyl group (-CH3) at the 2-position. This specific arrangement of functional groups dictates its chemical reactivity and physical behavior.

Reactivity and Functional Group Chemistry

The compound's reactivity is largely influenced by its functional groups: the carboxylic acid (-COOH) and the aryl bromide (Ar-Br). The carboxylic acid group allows for typical reactions such as esterification with alcohols, salt formation with bases, and reduction to alcohols. The bromine atom on the aromatic ring is susceptible to nucleophilic aromatic substitution under specific conditions and can participate in various metal-catalyzed cross-coupling reactions, such as Suzuki, Heck, or Sonogashira couplings. These reactions are instrumental in building more complex molecular architectures, making it a versatile intermediate for custom synthesis and R&D projects.

Spectroscopic Data for Identification and Characterization

Spectroscopic techniques are essential for confirming the identity and purity of chemical compounds. For 5-Bromo-4-methoxy-2-methylbenzoic acid:

• Nuclear Magnetic Resonance (NMR): Both ¹H NMR and ¹³C NMR spectra provide detailed information about the proton and carbon environments, respectively, allowing for precise structural elucidation. Characteristic signals for the aromatic protons, methoxy group, methyl group, and the carboxylic acid proton are observed. The ¹H NMR spectrum typically shows signals for the aromatic protons, the methoxy protons around 3.8 ppm, and the methyl protons around 2.5 ppm. The ¹³C NMR spectrum reveals signals for the nine distinct carbon atoms, including the carbonyl carbon of the carboxylic acid, aromatic carbons, methoxy carbon, and methyl carbon.
• Infrared (IR) Spectroscopy: IR spectroscopy confirms the presence of key functional groups. A strong, broad absorption in the 2500-3300 cm⁻¹ range indicates the O-H stretch of the carboxylic acid due to hydrogen bonding. A sharp, strong band between 1670-1725 cm⁻¹ confirms the C=O stretch of the carboxylic acid. Absorptions related to aromatic C-H stretching (3000-3100 cm⁻¹) and C-O stretching of the methoxy group (1000-1300 cm⁻¹) are also present.
• Mass Spectrometry (MS): Mass spectrometry provides molecular weight confirmation and fragmentation patterns. The molecular ion peak at m/z 245 (for the isotope ⁷⁹Br) and 247 (for ⁸¹Br) helps confirm the molecular formula. Characteristic fragmentation patterns, such as the loss of OH, COOH, or Br, further aid in identification.

Stability and Storage Recommendations

5-Bromo-4-methoxy-2-methylbenzoic acid is generally stable under recommended storage conditions. To maintain its purity and prevent degradation, it should be stored in a cool, well-ventilated place, away from direct sunlight, heat, and incompatible materials. As a responsible manufacturer and supplier, we provide detailed storage recommendations to ensure product longevity and efficacy. If you are looking to purchase this compound for your R&D, understanding these properties will ensure its optimal performance in your applications.