The hydrogenation of cyclododecene by lithium naphthalenide and nickel chloride dihydrate

This report describes an alternative method to catalytic hydrogenation of alkenes, exemplified by the transformation of cyclododecene into cyclododecane. We believe this experiment would be suitable for final-year undergraduate students. Students will learn how to reduce an alkene to an alkane in the absence of external hydrogen, through a pathway that generates molecular hydrogen from water and an active transition metal. The activation of the latter is itself interesting, since it involves the combination of lithium and naphthalene as a reducing system, thus introducing the role of naphthalene as an electron carrier. We also consider the experiment very complete and useful for the overall chemistry education of the students because of the advanced laboratory techniques they will exercise: (i) partial dehydration of a transition metal salt under vacuum, (ii) the reaction itself, with color changes indicating the presence of certain species, (iii) filtration and evaporation of solvents, (iv) chromatographic separation, and (v) characterization by chromatographic and spectroscopic techniques.