I. Determination of an Acetylenic Hydrocarbon (3-Hexyne) in Carbon Tetrachloride and in Aqueous Solution. II. Complex Formation by the Carbon-Carbon Triple Bond

Using 3-hexyne, the method of Lucas and Pressman (1) for determining acetylenic hydrocarbons by bromlnat1on with a mercuric salt catalyst in the absence of light and oxygen was studied in detail. Determinations of 3-hexyne in carbon tetrachloride solution yielded a two-phase system of considerable complexity, the rate of bromination being dependent upon several factors. From 99 to 102% of the 3-hexyne taken was found in numerous runs, the average deviation being usually less than 1%. Determination of 3-hexyne in aqueous solutions yielded a more simple system but gave the same resu1ts if oxygen was excluded from the solutions. The nature of the oxygen interference was not established. Some evidence indicates that the process involved is not true bromination, but rather some more complicated reaction-. It was found by a distribution method that 3-hexyne complexes with silver ion in aqueous solutions, but does not complex with bipositive cadmium, copper, nickel, cobalt, or zinc ions. A rapid reaction with mercuric salts precluded any conclusion about complexing. The evidence for cuprous chloride or for cuprous ion is inconclusive, but no complexing is indicated. Two silver ions complex stepwise with one molecule of 3-hexyne, the argentation constants being 19.1 and 0.22 respectively. The interaction is much weaker than that of olefins, but several times stronger than that of the aromatic hydrocarbons.