Deduce the structure of each compound from the information given. All unknowns in this problem have molecular formula C₈H₁₂.
(a) Upon catalytic hydrogenation, unknown W gives cyclooctane. Ozonolysis of W, followed by reduction with dimethyl sulfide, gives octanedioic acid, HOOC–(CH₂)₆–COOH. Draw the structure of W.

Verified step by step guidance

1. Step 1: Analyze the molecular formula C8H12. This indicates that the compound is unsaturated because the hydrogen count is less than the maximum possible for a saturated hydrocarbon (C8H18). The degree of unsaturation can be calculated using the formula: \( \text{Degree of Unsaturation} = \frac{2C + 2 - H}{2} \). Substituting \( C = 8 \) and \( H = 12 \), we find \( \text{Degree of Unsaturation} = \frac{2(8) + 2 - 12}{2} = 3 \). This means the compound has three degrees of unsaturation, which could correspond to rings or double bonds.
2. Step 2: Consider the information that catalytic hydrogenation of W gives cyclooctane. This suggests that W contains a single ring structure (cyclooctane is a saturated cyclic compound) and that the unsaturation in W is due to double bonds rather than additional rings.
3. Step 3: Examine the ozonolysis product. Ozonolysis cleaves double bonds and forms carbonyl-containing compounds. The product given is octanedioic acid, \( \text{HOOC-(CH2)6-COOH} \), which is a dicarboxylic acid with eight carbons. This indicates that W contains two double bonds, and their cleavage leads to the formation of the two carboxylic acid groups at the ends of the chain.
4. Step 4: Deduce the structure of W based on the above information. Since W has a single ring (cyclooctane after hydrogenation) and two double bonds, the structure of W must be a cyclooctadiene. The positions of the double bonds must be such that ozonolysis produces octanedioic acid. This implies that the double bonds are located opposite each other in the ring, leading to the cleavage of the ring into a linear dicarboxylic acid.
5. Step 5: Draw the structure of W. The structure is \( \text{1,5-cyclooctadiene} \), where the double bonds are at positions 1 and 5 of the cyclooctane ring. This arrangement satisfies the molecular formula, the degree of unsaturation, and the ozonolysis product.

Key Concepts

Catalytic Hydrogenation

Catalytic hydrogenation is a chemical reaction that involves the addition of hydrogen (H2) to unsaturated organic compounds, typically in the presence of a catalyst such as palladium, platinum, or nickel. This process converts alkenes or alkynes into alkanes, effectively saturating the molecule. In the context of the question, the hydrogenation of compound W yielding cyclooctane indicates that W must contain a structure that can be fully saturated to form this cyclic alkane.

Ozonolysis

Ozonolysis is a reaction involving the cleavage of alkenes or alkynes using ozone (O3), resulting in the formation of carbonyl compounds such as aldehydes or ketones. The reaction typically proceeds through the formation of an ozonide intermediate, which is then reduced to yield the final products. In this case, the ozonolysis of compound W leading to octanedioic acid suggests that W contains a double bond that, when cleaved, produces the dicarboxylic acid structure.

Molecular Formula Interpretation

The molecular formula provides essential information about the number and types of atoms in a compound. For C8H12, the formula indicates that the compound contains eight carbon atoms and twelve hydrogen atoms, suggesting a degree of unsaturation. This unsaturation can be due to double bonds or rings in the structure. Understanding how to interpret this formula is crucial for deducing the possible structures of compound W, especially in relation to the reactions it undergoes.