Draw the structure of a compound with molecular C8H14 that reacts with one equivalent of H2 over Pd/C to form a meso compound

Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics

Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook

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Bruice 8th Edition

Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics

Problem 60

Chapter 6, Problem 60

Draw the structure of a compound with molecular C₈H₁₄ that reacts with one equivalent of H₂ over Pd/C to form a meso compound

Verified step by step guidance

Step 1: Analyze the molecular formula C8H14. The degree of unsaturation can be calculated using the formula: \( \text{Degree of Unsaturation} = rac{2C + 2 - H}{2} \). For C8H14, \( \text{Degree of Unsaturation} = rac{2(8) + 2 - 14}{2} = 2 \). This indicates the presence of two double bonds, one triple bond, one ring and one double bond, or two rings in the structure.

Step 2: The problem states that the compound reacts with one equivalent of H2 over Pd/C to form a meso compound. This suggests that the compound contains a single double bond that can be hydrogenated, and the resulting product must have a plane of symmetry (a characteristic of meso compounds).

Step 3: To form a meso compound upon hydrogenation, the starting compound must have a symmetrical structure. A likely candidate is a compound with a double bond in a symmetrical position, such as a cis-alkene in a cyclic structure (e.g., a cycloalkene).

Step 4: Consider a symmetrical cyclic structure with one double bond, such as 1,2-cyclooctadiene. Upon hydrogenation, the double bond is reduced, and the resulting compound (cyclooctane) is meso because it has a plane of symmetry.

Step 5: Draw the structure of the compound. The starting compound is a symmetrical cycloalkene (e.g., cis-1,2-cyclooctadiene), and the product after hydrogenation is a meso compound (cyclooctane). Ensure the double bond is placed in a position that maintains symmetry in the starting structure.

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Key Concepts

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

Molecular Formula and Structure

The molecular formula C8H14 indicates a compound with eight carbon atoms and fourteen hydrogen atoms. Understanding how to derive the structural representation from this formula is crucial, as it helps in visualizing the compound's connectivity and functional groups. The structure must also accommodate the reactivity with hydrogen, suggesting the presence of unsaturation, such as double bonds or rings.

Hydrogenation Reaction

Hydrogenation is a chemical reaction where hydrogen (H2) is added to a compound, typically in the presence of a catalyst like palladium on carbon (Pd/C). This process is essential for converting unsaturated compounds into saturated ones. In this case, the reaction with one equivalent of H2 implies that the compound has at least one double bond that can be reduced, leading to the formation of a meso compound.

Meso Compounds and Symmetry

Meso compounds are achiral molecules that contain multiple stereocenters but possess an internal plane of symmetry. This symmetry allows for superimposition of the molecule on its mirror image, which is a key characteristic of meso compounds. When drawing the structure, it is important to ensure that the resulting product after hydrogenation exhibits this symmetry, confirming its classification as a meso compound.

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Related Practice

Textbook Question

a. Which of the following reactions has the larger ∆S° value?

b. Is the ∆S° value positive or negative?

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Textbook Question

Draw structures for the following:

c. (3Z,5Z)-4,5-dimethyl-3,5-nonadiene

d. (3E,5E)-2,5-dibromo-3,5-octadiene

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Textbook Question

Given the reaction coordinate diagram for the reaction of A to form G, answer the following questions:

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a. How many intermediates are formed in the reaction?

b. Which letters represent transition states?

c. What is the fastest step in the reaction?

d. Which is more stable: A or G?

e. Does A or E form faster from C?

f. Which is the more stable intermediate?

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Textbook Question

For a reaction carried out at 25 °C with an equilibrium constant of 1 × 10^-3, to increase the equilibrium constant by a factor of 10:

a. how much must ∆G° change?

b. how much must ∆H° change if ∆S° = 0 kcal mol^-1K^-1?

c. how much must ∆S° change if ∆H° = 0 kcal mol^-1?

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Textbook Question

Using curved arrows, show the mechanism of the following reaction:

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Textbook Question

a. What is the equilibrium constant for a reaction that is carried out at 25 °C (298 K) with ∆H° = 20 kcal/mol and ∆S° = 5.0 × 10^-2 kcal mol^-1 K^-1?

b. What is the equilibrium constant for the same reaction carried out at 125 °C?

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