3,5-Di-tert-butyl-4-hydroxybenzaldehyde hemihydrate is a high-purity aromatic aldehyde widely used in organic synthesis, pharmaceutical intermediates, and antioxidant research. As a key building block, it is employed in the synthesis of hindered phenolic antioxidants, which are critical for stabilizing polymers, plastics, and rubber against thermal and oxidative degradation. In pharmaceutical development, it serves as an intermediate for preparing anti-inflammatory, analgesic, and cardiovascular drugs, leveraging its unique steric hindrance and phenolic hydroxyl reactivity. Additionally, it is utilized in academic research for studying structure-activity relationships of phenolic compounds and in the development of new synthetic methodologies for aromatic aldehydes. Its stable crystalline form and high purity make it suitable for GMP-compliant production and laboratory-scale synthesis.

GHS Classification: H315 (Causes skin irritation), H319 (Causes serious eye irritation), H335 (May cause respiratory irritation). Signal Word: Warning. Acute oral LD50 >2000 mg/kg (low toxicity). Skin contact may cause redness, itching, or mild dermatitis; wear nitrile gloves and protective clothing when handling. Eye contact can lead to severe irritation and conjunctivitis; use splash-proof goggles and rinse eyes with plenty of water for at least 15 minutes if exposed. Inhalation of dust may irritate the respiratory tract, causing cough or shortness of breath; use in a fume hood or well-ventilated area and wear a dust mask. No evidence of carcinogenicity, mutagenicity, or reproductive toxicity. Harmful to aquatic life; prevent discharge into waterways. Store separately from strong oxidants and acids; neutralize spills with inert absorbent material and dispose of according to local hazardous waste regulations.