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Terpene Structural Problems

Chemical and spectroscopic information concerning three terpenes is provided. Using this together with the isoprene rule, you should be able to draw structural formulas for these compounds. Use the Drawing Window on the left. When you are finished, check your answer by pressing the appropriate Check Structure button. A help screen is available for the drawing window.

You have to enable Java and JavaScript on your machine ! 1. Terpene I is an optically active liquid, formula C10H16. Hydrogenation ( 2 H2 + Pt ) gives an optically inactive C10H20 product. The uv-visible spectrum of I shows strong absorbtion at λmax = 265nm. Ozonolysis of I, followed by hydrogen peroxide treatment, yields 2-isopropylsuccinic acid as the only identified product.
2. Terpene II is a pleasant smelling, optically inactive liquid, formula C10H18O. Hydrogenation ( 2 H2 + Pt ) of II gives a C10H22O product, which on Jones' oxidation yields a C10H20O2 carboxylic acid. Ozonolysis of the original terpene, II, followed by hydrogen peroxide treatment produces 4-oxo-pentanoic acid and acetone in equal molar amounts. Other products may be formed, but are not identified.
3. Terpene III is a pleasant smelling, optically active liquid, formula C10H14O. The infrared spectrum of III has a strong carbonyl absorption at 1675 cm-1, and its 1H nmr spectrum shows two methyl resonance peaks near δ 1.8 ppm and three vinyl hydrogen signals. Hydrogenation ( 2 H2 + Pt ) of III gives a C10H18O product, which has a carbonyl band at 1715 cm-1 in the infrared. Ozonolysis of the original terpene, III, followed by hydrogen peroxide treatment produces a keto diacid, CH3COCH(CH2CO2H)2. Other products may be formed, but are not identified.
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Virtual Textbook: Practice Problems — Structure of Terpenes, figure 1
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