Question

Using your reaction roadmap as a guide, show how to convert the starting trans-alkene to the cis-alkene in high yield. Show all intermediate molecules synthesized along the way.

Short answer

Question: Describe the two-step process to convert a trans-alkene into a cis-alkene in high yield, showing all the intermediate molecules along the way. Answer: The two-step process to convert a trans-alkene into a cis-alkene involves hydrogenation and syn-hydroxylation. In the first step, the trans-alkene undergoes hydrogenation using a catalyst like palladium on carbon (Pd/C) and hydrogen gas (H2) as the reagent, resulting in an alkane. In the second step, the alkane is converted into a cis-alkene using syn-hydroxylation with osmium tetroxide (OsO4) and hydrogen peroxide (H2O2) as reagents. This process allows for efficient conversion of the trans-alkene to its cis-alkene isomer with good yield.

Step-by-step solution

Hydrogenation of the trans-alkene

To convert the trans-alkene into a cis-alkene, we first need to hydrogenate the double bond using a suitable hydrogenation catalyst like palladium on carbon (Pd/C) and hydrogen gas (H2) as the reagent. This reaction will convert the trans-alkene into an alkane by breaking the double bond and adding two hydrogen atoms. The reaction is as follows: trans-alkene + Pd/C + H2 -> alkane

Syn-hydroxylation of the alkane

After fully hydrogenating the trans-alkene, we will convert the alkane into a cis-alkene using syn-hydroxylation. In this reaction, osmium tetroxide (OsO4) and a hydrogen peroxide (H2O2) solution are used as reagents. This step will convert the saturated alkane into a cis-alkene by removing two hydrogen atoms from adjacent carbons, generating a double bond between the carbons with the same stereochemistry (i.e., cis). The reaction is as follows: alkane + OsO4 + H2O2 -> cis-alkene By following this two-step process, the trans-alkene can be efficiently converted to its cis-alkene isomer with good yield.