Hydrogen Bromide → 3,6-Dibromo-2-methylpyridine

Participants

Reaction Conditions

Reaction Steps

5-Bromo-2-amino-6-picoline (7.0 kg) and 5-bromo-2-amino-6-picoline hydrobromide (7.0 kg) (based on the starting material analyses, this was equal to 11 kg or 41 mol of starting material) are dissolved into 48% hydrobromic acid (107.0 kg, 635 mol, 15.49 eq) at <35° C. The solution was cooled to 2° C. and bromine (27.3 kg, 171 mol, 4.17 eq) was charged over 45 min at 0-5° C. A solution of sodium nitrite (8.1 kg, 117 mol, 2.86 eq) in 20 L of water was charged over 1.5 hours at −1 to 5° C. The contents were held one hour and the pH was adjusted to 12.5 using 50% aqueous sodium hydroxide (70.0 kg). The contents were warmed to 20° C. over one hour and the solids were collected in a polypropylene bag on a centrifuge. The solids were washed with water (75 L) to produce 12.0 kg of moist 2,5-dibromo-6-picoline, determined to be 83 wgt % product (68% yield). Part of this was dried for the purposes of recording the 13C NMR spectrum: 13C NMR (400 MHz, CDCl3) δ 158.8, 141.9, 139.4, 126.7, 120.6, 24.7.

Provenance & Evidence