Positional isomers are usually not obtained when an alkene is oxymercurated, although several exceptions have been noted (1, 2, 3). However these exceptions do not occur unexpectedly. On the other hand Sand and Singer (4,5) reported two pairs of isomers which were formed by oxymercuration of 2,6-dimethylhepten-5-ol-2. They implied by analogy with the oxymercuration products from -terpineol that these were diastereomers, but this is obviously impossible since only one asymmetric carbon atom would be present in the products from dimethylheptenol.The oxymercuration of 2,6-dimethylhepten-5-ol-2 was carried out by Sand and Singer with mercuric acetate in water, and potassium iodide was added subsequently. The pair of isomers with the composition CgHigChHgl (II, X = iodide) was alkali-soluble and wras represented as 2,6-dimethyl-3-iodomercuriheptanediol-2,6. The other pair, containing one molecule less of the elements of wrater, was designated by the structure 2,2,6,6-tetramethyl-3-iodomercuritetrahydropyrans. These structure designations wrere assumed solely by analogy with the three oxymercurials which Sand and Singer obtained from a-terpineol.Each of the pairs from dimethylheptenol comprised an oil and a crystalline solid. Furthermore the oil could be easily, or wras spontaneously converted to the solid. In general, oxyalkanemercurials are reasonably stable except in acidic media (3, 6); furthermore an alkene of specific configuration has always been