In a
3-l., three-necked, round-bottomed flask fitted with a powerful slow-speed stirrer having a Teflon® blade, a 500-ml. dropping funnel, and a thermometer arranged to dip into the liquid is placed
588 g. (366 ml., 6 moles) of concentrated sulfuric acid. The flask is surrounded by an ice-salt mixture, the stirrer started, and
1216 g. (1170 ml., 12 moles) of acetic anhydride (Note
1) is added at such a rate that the temperature does not rise above 20° (Note
2). The separatory funnel is removed and
912 g. (6 moles) of coarsely powdered D,L-camphor is added (Note
3). The flask is then closed with a stopper and stirring is continued until the
camphor is dissolved. The stirrer is replaced by a stopper, the
ice bath allowed to melt, and the mixture left to stand for 36 hours (Note
4). The
camphorsulfonic acid is collected on a
suction filter and washed with
ether (Note
5). After being dried in a
vacuum desiccator at room temperature, the nearly white crystalline product weighs
530–580 g. (
38–42%). It melts at
202–203° with rapid decomposition and is relatively pure (Note
6).