Ch.13 - Properties of Solutions

Problem 7

Chapter 13, Problem 7

The structures of vitamins E and B6 are shown below. Predict which is more water soluble and which is more fat soluble. [Section 13.3]

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Identify the structural features of each vitamin that influence solubility.

Vitamin E has a long hydrocarbon tail, which is nonpolar and hydrophobic, making it more fat soluble.

Vitamin B6 contains several polar groups, such as hydroxyl (OH) groups, which can form hydrogen bonds with water, making it more water soluble.

Consider the overall polarity of each vitamin: Vitamin E is less polar due to its hydrocarbon tail, while Vitamin B6 is more polar due to its functional groups.

Conclude that Vitamin E is more fat soluble and Vitamin B6 is more water soluble based on their structural features.

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Key Concepts

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

Solubility Principles

Solubility refers to the ability of a substance to dissolve in a solvent. Water solubility is influenced by the presence of polar functional groups, which interact favorably with water molecules, while fat solubility is associated with nonpolar characteristics that dissolve in lipids. Understanding these principles helps predict how vitamins behave in biological systems.

Chemical Structure of Vitamins

The chemical structure of vitamins, including the presence of functional groups such as hydroxyl (-OH) or carboxyl (-COOH), plays a crucial role in determining their solubility. For instance, vitamins with more hydrophilic groups tend to be more water-soluble, while those with long hydrocarbon chains are typically more fat-soluble. Analyzing the structures of vitamins E and B6 is essential for making solubility predictions.

Hydrophilic vs. Hydrophobic

Hydrophilic substances are attracted to water and tend to dissolve in it, while hydrophobic substances repel water and are more soluble in fats. This distinction is vital when predicting the solubility of vitamins, as it directly relates to their functional roles in the body. Recognizing which vitamin has hydrophilic or hydrophobic characteristics aids in understanding their absorption and transport mechanisms.

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