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Ch. 9 - Alkenes II: Oxidation and Reduction
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 9 - Alkenes II: Oxidation and ReductionProblem 45l(ix,x)
Chapter 8, Problem 45l(ix,x)

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (ix) H2, Pd/C; and (x) D2, Pd/C.
(l)

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1
Step 1: Analyze the structure of the given alkene. The molecule contains a double bond, which is the reactive site for hydrogenation reactions. The double bond is located between two carbon atoms in the chain.
Step 2: Understand the reaction conditions. (ix) H₂, Pd/C involves catalytic hydrogenation, where molecular hydrogen (H₂) adds across the double bond in the presence of a palladium catalyst. This results in the conversion of the alkene to an alkane by adding two hydrogen atoms to the carbons of the double bond.
Step 3: For (x) D₂, Pd/C, the reaction is similar to (ix), but instead of H₂, deuterium gas (D₂) is used. Deuterium is an isotope of hydrogen, so the double bond will be saturated with deuterium atoms instead of hydrogen atoms.
Step 4: Predict the stereochemistry of the product. The addition of H₂ or D₂ across the double bond occurs in a syn fashion, meaning both hydrogen or deuterium atoms will add to the same face of the double bond. This is due to the surface mechanism of the Pd/C catalyst.
Step 5: Consider the chirality of the molecule. If the addition of H₂ or D₂ creates new chiral centers, the product will be a mixture of stereoisomers (enantiomers or diastereomers) depending on the original structure of the alkene.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hydrogenation

Hydrogenation is a chemical reaction that involves the addition of hydrogen (H₂) to an alkene or alkyne, converting it into an alkane. This reaction typically requires a catalyst, such as palladium on carbon (Pd/C), which facilitates the breaking of the double bond in the alkene, allowing hydrogen atoms to add across it. The result is a saturated hydrocarbon, which is generally more stable than the original unsaturated compound.
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Deuteration

Deuteration is similar to hydrogenation but involves the addition of deuterium (D₂), a stable isotope of hydrogen, instead of regular hydrogen. This process also requires a catalyst like Pd/C and results in the formation of deuterated alkanes. Deuteration is often used in organic chemistry for tracing reactions and studying mechanisms due to the unique properties of deuterium compared to hydrogen.

Catalytic Activity of Pd/C

Palladium on carbon (Pd/C) is a widely used catalyst in organic reactions, particularly in hydrogenation and deuteration processes. The palladium provides active sites for the adsorption of hydrogen or deuterium, facilitating the addition to alkenes. The carbon support enhances the dispersion of palladium, increasing its surface area and catalytic efficiency, making it an effective choice for these types of reactions.
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