Sesquiterpenoids. Part IV. The stereochemistry of humulene: X-ray analysis of the humulene–silver nitrate adduct

Abstract

X-Ray analysis of the humulene–silver nitrate adduct has established the stereochemistry of humulene, the predominant sesquiterpene of hop oil. Each Ag⁺ ion is bonded to one carbon–carbon double bond at an average Ag⁺⋯ C distance of 2·38 Å. The adduct crystallises in the monoclinic system, with a= 15·06, b= 6·95, c= 17·94 Å, β= 98° 55′; there are four C₁₀H₂₄,2AgNO₃ units in the cell and the space group is P2₁/c. The atoms were located in three-dimensional electron-density distributions and their positions refined by the method of least squares. The final discrepancy, R, over 2344 independent reflections is 16·1%.