Preparation of isonitrosocamphor
56 g camphor are dissolved in 250 ml of dry ether in a large flask and 7.6 g of sodium wire added. The mixture is cooled with ice water, after which 39 g of isoamyl nitrite are added in small portions with stirring and continued cooling. The addition of the nitrite usually takes 10-15 minutes. Reaction is completed in several hours when no sodium is left. Then ice water is added (if there is no sodium left!!!), giving a reddish solution of the sodium salt of isonitrosocamphor. Unchanged camphor and borneol, formed by reduction are removed by shaking out cautiously several times with benzene, and the aqueous layer is filtered. Dilute acetic acid is then added until no further precipitation occurs. The yield of crude isonitrosocamphor, which is, a mixture of isomers, is about 22 g. The low-melting isomer is converted into the high-melting form when the dried mixture is heated at 150° for a few minutes. After recrystallization from ligroin isonitrosocamphor melts at 152-153° C.
An advanced laboratory manual of organic chemistry, M. Heidelberger, 54-55, 1923