Question

Eleostearic acid, \(\mathrm{C}_{18} \mathrm{H}_{30} \mathrm{O}_{2}\), is a rare fatty acid found in the tung oil used for finishing furniture. On ozonolysis followed by treatment with zinc, eleostearic acid furnishes one part pentanal, two parts glyoxal \(\left.\) (OHC-CHO), and one part 9-oxononanoic acid [OHC(CH \(\left.\left._{2}\right)_{7} \mathrm{CO}_{2} \mathrm{H}\right] .\) What is the structure of eleostearic acid? (Note that alkenes undergo ozonolysis followed by treatment with zinc to give carbonyl compounds in which each of the former \(\mathrm{C}=\mathrm{C}\) carbons becomes a \(\mathrm{C}=\mathrm{O}\) carbon.

Short answer

Eleostearic acid has three double bonds, making it a conjugated fatty acid.

Step-by-step solution

Understand Ozonolysis

Ozonolysis is a chemical reaction where alkenes (compounds with C=C double bonds) are cleaved by ozone (O3) into carbonyl compounds (compounds with C=O double bonds). When treated further with zinc, aldehydes or ketones are formed as the oxygen atoms from ozone replace the double bonds.

Analyze Products Formed

We know from the problem statement that ozonolysis of eleostearic acid yields 1 part pentanal, 2 parts glyoxal, and 1 part 9-oxononanoic acid. This suggests that the structure of eleostearic acid has three double bonds, each of which cleaves to form these carbonyl-containing products.

Map the Products to the Precursor

Each product suggests a position where a C=C bond used to be in eleostearic acid. Pentanal forms from a structure portion: R-CH=CH-R. Glyoxal formation suggests a segment R-CH=CH2. 9-oxononanoic acid indicates a section ending in CO2H.

Construct the Structure

Taking into account the three products, construct the simplest structure of eleostearic acid (C18H30O2) with three double bonds corresponding to the three different cleaved products. Where the product originated from will have a C=C in the original structure.

Verify the Structure

Ensure the constructed structure satisfies the molecular formula of eleostearic acid (C18H30O2) and each double bond location corresponds correctly to the products of ozonolysis. The eleostearic acid derived structure is consistent with the molecular fragments given by ozonolysis.

Key concepts

Eleostearic acid

Eleostearic acid is a unique and rare fatty acid primarily found in tung oil, which is often used for finishing furniture. Structurally, it is described by the formula \( \mathrm{C}_{18} \mathrm{H}_{30} \mathrm{O}_{2} \). The significance of eleostearic acid lies in its conjugated triene system, which includes three double bonds that can undergo chemical reactions like ozonolysis. Understanding the uniqueness of eleostearic acid helps us comprehend how its multi-double-bond nature impacts its reactivity and the type of chemical products formed during reactions. The ozonolysis of eleostearic acid produces various carbonyl compounds that indicate the locations of its C=C double bonds.

Alkene cleavage

Alkene cleavage is an essential chemical process where C=C double bonds in alkenes are broken, often creating new molecules with different functional groups. Ozonolysis is a famous method of cleavage used to convert alkenes into carbonyl compounds.

• Ozone (\( \mathrm{O}_3 \)) reacts with the alkene, creating unstable intermediates.
• Further reduction, often using zinc, leads to stable carbonyl compounds like aldehydes and ketones.

This process showcases how the versatile nature of double bonds allows for the transformation of simple alkenes into complex organic molecules, thus playing a critical role in organic synthesis.

Carbonyl compounds

Carbonyl compounds are a group of organic compounds characterized by the presence of a carbon-oxygen double bond \( (\mathrm{C}=\mathrm{O}) \). They are typically formed during reactions like ozonolysis where alkenes are converted into carbonyl-containing products.

• The simplest carbonyl compounds are aldehydes and ketones, which are usually volatile and reactive.
• In the context of eleostearic acid, carbonyl compounds such as pentanal, glyoxal, and oxononanoic acid are indicators of where the double bonds existed.

Mastery of carbonyl compound behavior and formation is crucial in understanding many biochemical pathways and industrial applications.

Chemical reaction analysis

Chemical reaction analysis involves studying the reactants, products, and transformative processes that define a chemical reaction. Ozonolysis offers an excellent example of how analytical chemistry determines the structure of compounds like eleostearic acid.

• By examining the products formed — such as pentanal, glyoxal, and oxononanoic acid — we deduce the positioning of the C=C bonds in the precursor molecule.
• Analysis confirms that three distinct products correlate with the presence of three original double bonds.

This methodical deconstruction of reactions allows chemists to infer structures from fragmented evidence, providing invaluable insights in both research and practical applications.