Show how you would accomplish the following synthetic transformations. Show all intermediates.
f. cyclodecyne → cis-cyclodecene

Verified step by step guidance

1. Step 1: Analyze the transformation. The starting material is cyclodecyne, which contains a triple bond, and the target product is cis-cyclodecene, which contains a double bond in the cis configuration. This indicates that the reaction involves the reduction of the triple bond to a double bond while maintaining the cis geometry.
2. Step 2: Select an appropriate reagent for the reduction. To selectively reduce an alkyne to a cis-alkene, use a Lindlar catalyst. The Lindlar catalyst is a palladium catalyst poisoned with lead or quinoline, which prevents further reduction to an alkane and ensures the formation of a cis-alkene.
3. Step 3: Write the reaction mechanism. The Lindlar catalyst facilitates the addition of hydrogen (H₂) to the triple bond in a syn fashion, meaning both hydrogen atoms are added to the same side of the molecule. This syn addition results in the cis configuration of the double bond.
4. Step 4: Identify the intermediate. During the reaction, the triple bond is partially reduced to form a cis-alkene. No other intermediates are formed in this specific reaction pathway.
5. Step 5: Confirm the stereochemistry. The use of the Lindlar catalyst ensures that the double bond in the product is in the cis configuration, as opposed to the trans configuration, which would require a different reagent such as sodium in liquid ammonia.

Key Concepts

Cyclodecyne Structure

Cyclodecyne is a cyclic alkyne with a ten-membered carbon ring containing a triple bond. Understanding its structure is crucial for planning synthetic transformations, as the presence of the triple bond influences reactivity and the types of reactions that can be employed to convert it into other compounds.

Hydrogenation Reactions

Hydrogenation is a chemical reaction that involves the addition of hydrogen (H2) to unsaturated hydrocarbons, such as alkynes and alkenes. This process is essential for converting cyclodecyne into cis-cyclodecene, as it reduces the triple bond to a double bond while maintaining the stereochemistry required for the cis isomer.

Stereochemistry of Alkenes

Stereochemistry refers to the spatial arrangement of atoms in molecules and is particularly important in alkenes, where the orientation of substituents around the double bond can lead to different isomers. For the synthesis of cis-cyclodecene, it is vital to control the stereochemistry during the hydrogenation process to ensure the correct geometric isomer is formed.