SOLUBILITY

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Lab 3: Solubility of Organic Compounds

Objectives:
Understanding the relative solubility of organic compounds in various solvents.
Exploration of the effect of polar groups on a nonpolar hydrocarbon skeleton.

Introduction: The solubility of a solute (a dissolved substance) in a solvent (the dissolving medium) is the most important chemical principle underlying three major techniques you will study in the organic chemistry laboratory: crystallization, extraction, and chromatography. In this experiment on solubility you will gain an understanding of the structural features of a substance that determine its solubility in various solvents. This understanding will help you to predict solubility behavior and to understand the techniques that are based on this property.

In one part of this experiment, you will determine whether a solid organic compound is soluble or insoluble in a given solvent. You should keep in mind that this is actually an over simplification since some solids may be partially soluble in a given solvent. If the organic compound being dissolved in a solvent is a liquid, then it is sometimes more appropriate to say that the compound and the solvent are miscible (mix homogeneously in all proportions). Likewise, if the liquid organic compound is insoluble in the solvent, then they are immiscible (do not mix, and form two liquid phases).

A major goal of this experiment is to learn how to make predictions about whether or not a substance will be soluble in a given solvent. This is not always easy to do, even for an experienced chemist. However there are some guidelines which will often make it possible for you to make a good guess about the solubilities of compounds in specific solvents. In discussing these guidelines it is helpful to separate the types of solutions we will be looking at into two categories: (1) Solutions in which both the solvent and the solute are covalent (molecular). (2) Ionic solutions in which the

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