Synthesis of cis-Stilbene

Calculate the volume (measured at STP) of carbon dioxide evolved 

The catalyst for this reaction is copper chromite, 2 CuO Cr203, a relatively inexpensive commercially available catalyst used for both hydrogenation and dehydrogenation as well as decarboxylation. 

Decarboxylation of -a-phenylcinnamic acid is effected by refluxing the acid in quinoline in the presence of a trace of copper chromite catalyst both the basic properties and boiling point (237°C) of quinoline make it a particularly favorable solvent. Z-Stilbene, a liquid at room temperature, can be characterized by trans addition of bromine to give the crystalline -dibromide. A little meso-dibromide derived from -stilbene in the crude hydrocarbon starting material is easily separated by virtue of its sparing solubility. 

the structure is much more symmetrical than that of the + (or -) dibromide. X-ray diffraction measurements of the dibromides in the solid state confirm the conformations indicated in Fig. 1. The Br-Br distances found are me5o-dibromide, 4.50 A -dibromide, 3.85 A. The difference in symmetry of the two optically inactive isomers accounts for the marked contrast in properties  

Material that has darkened in storage should be redistilled over a little zinc dust. 

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