Textbook Question
Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (i) Br2 (ii) Cl2
(l)
10. Addition Reactions
Hydrogenation
1:22 minutesProblem 82f
Textbook Question
Draw the products of the following reactions. If the products can exist as stereoisomers, show which stereoisomers are formed
f. 1,2-dideuteriocyclohexene + H2, Pd/C
Verified step by step guidance1
Step 1: Identify the type of reaction taking place. In this case, the reaction involves the addition of hydrogen (H2) to an alkene (1,2-dideuteriocyclohexene) in the presence of a catalyst (Pd/C). This is a catalytic hydrogenation reaction, which converts alkenes to alkanes by adding hydrogen across the double bond.
Step 2: Analyze the structure of the reactant, 1,2-dideuteriocyclohexene. The molecule contains a cyclohexene ring with a double bond between two carbon atoms, and two deuterium atoms (D) attached to the carbons involved in the double bond. Deuterium is an isotope of hydrogen.
Step 3: Determine the stereochemical outcome of the reaction. Catalytic hydrogenation typically occurs via syn addition, meaning both hydrogen atoms are added to the same face of the double bond. This can lead to stereoisomers if the molecule has chiral centers after the reaction.
Step 4: Draw the product of the reaction. The double bond in 1,2-dideuteriocyclohexene is reduced to a single bond, resulting in cyclohexane. The two new hydrogen atoms are added to the carbons that previously formed the double bond, and the stereochemistry of the product depends on whether the addition occurs on the same face as the deuterium atoms or the opposite face.
Step 5: Show the stereoisomers formed. If the addition of hydrogen occurs on the same face as the deuterium atoms, one stereoisomer is formed. If the addition occurs on the opposite face, another stereoisomer is formed. Draw both possible stereoisomers, clearly indicating the relative positions of the hydrogen and deuterium atoms on the cyclohexane ring.
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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 unsaturated compound, typically alkenes or alkynes, in the presence of a catalyst such as palladium on carbon (Pd/C). This process converts double or triple bonds into single bonds, resulting in saturated hydrocarbons. Understanding hydrogenation is crucial for predicting the products of reactions involving alkenes.
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Stereoisomerism
Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. In the context of hydrogenation, the formation of stereoisomers can occur when a reaction leads to the creation of chiral centers or when different spatial arrangements of substituents around a double bond are possible. Recognizing potential stereoisomers is essential for accurately depicting reaction products.
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Cyclohexene Structure
Cyclohexene is a cyclic alkene with a six-membered carbon ring containing one double bond. Its structure allows for various conformations, which can influence the outcome of reactions such as hydrogenation. The presence of substituents, like deuterium in 1,2-dideuteriocyclohexene, can lead to different stereochemical outcomes during reactions, making it important to consider the initial structure when predicting products.
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