Explosion in preparation of 5-bromo-4(3H)-pyrimidinone
Thomas J. Dietsche; Bruce Powers
Agricultural Chemicals Process Research
Thermal & Reactive Chemicals
Dow Chemical Co.
Chemical & Engineering News (10 Jul 1995) Vol. 73, No. 28, pp. 4.
Powers We would like to report a serious experience we had using a
literature preparation of 5-bromo-4(3H)-pyrimidinone [J. Org. Chem.
50, 3073 (1985)]. Two moles (20-fold increase over literature
preparation) of 5-bromopyrimidine was dissolved in about 1,800 mL of
acetone. Over a four-hour period, a mixture of 1 L of peracetic acid
and 115 mL of concentrated sulfuric acid was added dropwise while
keeping the reaction below 20 
C. On four earlier runs, the
white solid product was filtered, washed with ether, and allowed to
air dry for two to four hours. This run was filtered late on a
Friday evening and allowed to air dry over the weekend. On Monday
morning, the powder-dry product was being scraped from a sintered
glass funnel to complete the neutralization of the hemiacid salt
when an explosion occurred.
Subsequent testing determined that the peroxide dimer of acetone was
the most likely cause of the explosion. This material is reported to
be both shock and friction sensitive and known to sublime at room
temperature. This reaction had been run numerous times in these and
other laboratories without any suggestion of the hazards. We had
scaled the reaction up from the literature preparation through
several intermediate levels before deciding to proceed in our
preparation of several kilograms of the desired pyrimidinone on the
2-molar scale.
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