Draw the structure of the product you would obtain on complete hydrogenation of the triacylglycerol in Problem 23.49. What is its name? Does it have a higher or lower melting temperature than the original triacylglycerol?

Verified step by step guidance

1. Identify the structure of the original triacylglycerol. A triacylglycerol consists of a glycerol backbone esterified with three fatty acid chains. These fatty acid chains may contain double bonds (unsaturated) or no double bonds (saturated).
2. Understand the process of complete hydrogenation. During hydrogenation, all double bonds in the unsaturated fatty acid chains are converted into single bonds by the addition of hydrogen (H₂) in the presence of a catalyst, such as nickel or platinum.
3. Draw the structure of the hydrogenated product. Replace all double bonds in the fatty acid chains with single bonds, ensuring that the resulting fatty acid chains are fully saturated. The glycerol backbone remains unchanged.
4. Name the product. The name of the product will depend on the specific fatty acids present in the original triacylglycerol. After hydrogenation, the fatty acids will be fully saturated, so their names will reflect this (e.g., oleic acid becomes stearic acid).
5. Compare the melting temperature. Fully saturated triacylglycerols have a higher melting temperature than their unsaturated counterparts because saturated fatty acid chains pack more tightly, leading to stronger intermolecular forces (van der Waals interactions).

Key Concepts

Triacylglycerol Structure

Triacylglycerols, or triglycerides, are esters formed from glycerol and three fatty acids. Their structure consists of a glycerol backbone attached to three long hydrocarbon chains, which can be saturated or unsaturated. The nature of these fatty acids significantly influences the physical properties of the triacylglycerol, including its melting temperature.

Hydrogenation Process

Hydrogenation is a chemical reaction that involves the addition of hydrogen to unsaturated fatty acids, converting double bonds into single bonds. This process typically results in the saturation of the fatty acid chains, leading to a more solid product. Complete hydrogenation of triacylglycerols transforms them into saturated fats, which alters their melting point and physical state.

Melting Temperature

The melting temperature of a fat is influenced by its fatty acid composition. Saturated fats, resulting from complete hydrogenation, generally have higher melting temperatures compared to unsaturated fats due to their straight-chain structure, which allows for tighter packing. Understanding the relationship between saturation and melting temperature is crucial for predicting the physical properties of the hydrogenated product.