FACILE SYNTHESIS AND PHYSICAL AND SPECTRAL CHARACTERIZATION OF 2,6-DI-TERT-BUTYL-4-NITROPHENOL (DBNP) - A POTENTIALLY POWERFUL UNCOUPLER OFOXIDATIVE-PHOSPHORYLATION

The compound 2,6-di-tert-butyl-4-nitrophenol (DBNP), a potentially pow erful uncoupler of ATP-generating oxidative phosphorylation, has been physically and spectroscopically characterized using X-ray crystallogr aphy, differential scanning calorimetry (DSC), thermal gravimetric ana lysis (TGA), GC-MS spectrometry, Fourier-transformed IR (FTIR) spectro photometry, UV-Vis spectrophotometry, and FT H-1 and C-13-NMR spectros copy. However, DBNP is not commercially available; therefore, it had t o be synthesized in the laboratory prior to toxicity studies. The DBNP was prepared from 2,6-di-tert-butylphenol (DBP) precursor in hexane t hrough an electrophilic aromatic substitution process using NO2. A col lective yield of 75% was obtained by using two empirically determined end points that prevented the coprecipitation of reaction by-products and resulted in the formation of DBNP in high purity. Excessive amount s of NO2 in reaction mixtures resulted in the decomposition of preform ed DBNP. With a pK(a) value of 6.8 and a higher degree of lipophilicit y, DBNP may prove to be a stronger uncoupler of oxidative phosphorylat ion than 2,4-dinitrophenol (pK(a) = 4.09) due to the expected enhancem ent of passive-diffusion kinetics across biological membranes at the p hysiological pH of 7.4. The present study is intended to provide analy tical toxicologists, industrial hygiene monitors, and other profession als involved in chemical health and safety with a comprehensive source of basic information on the synthesis and analytical chemistry of DBN P.