Aim: To determine and report the solubility behavior of the given sample:
Principle: The objective of this experiment is to investigate the solubility characteristic of some simple organic molecules and to look at relationships between the solubility properties of an organic molecule and its structure.
the leads to the important idea that structure dictates function which means that by knowing the structure of a molecule, we should be able to predict its "function" such as its solubility of an organic molecule is a useful skill. For example, it can be useful when trying to purify(e.g recrystalization: picking a suitable solvent) or isolate it from a multi-component reaction mixture(eg. via extraction), or when extracting a molecule from a natural source such as a plant, or designing a new pharmaceutical that needs to be soluble in the blood stream (aqueous and alkaline), the stomach (aqueous and acidic) or enter the central nervous system("fatty"). . For example, you will extract and then isolate caffeine from tea leaves -an "experiment" that you may perform several times per day while making tea(or similarly for coffee)! solubility is also an important consideration when performing reactions to synthesize molecules; usually, regents and starting materials are mixed together in a solution. The partitioning of drug molecules within the body between the blood and various tissues is also related to solubility properties.
The solubility of the molecule depends on several intermolecular forces such as ion dipole, solvent-solute, solvent-solvent, etc. A compound dissolves in water if it can form hydrogen bonds with water. During dissolution of a solid and liquid, the ions or molecules separate out and the spaces in between them are taken up by the formation of new bonds between solvent and the solute particles. In general, the solubility of organic compound gives valuable information regarding its chemical nature.
Most organic molecules are typically relatively non-polar and usually soluble in organic solvents (e.g diethyl ether, dichloromethane, chloroform, petroleum ether, hexanes etc.) but not in polar solvents like water. However, some organic molecules are more polar and therefore more soluble in water.
Requirements:
Chemicals:
- Diethyl ether
- Methanol
- Distilled water
- Ethanol
- 5% NaOH
- 5% HCl
- Conc H2SO4
- 5% NaHCO3
Glassware/ Apparatus:
- Micro spatula glass
- Glass rod
- Graduated Cylinder
- Latex bulb
- Transfer pipette
- pH paper
- Test tubes(6-10)
Procedures:
- Take few test tubes and label them as A,B,C,D.......and so on.
- To the first test tube and water, shake well and observe the solubility.
- To the second test tube add ether, shake well and observe the solubility.
- Take Ethanol as a solvent and observe solubility in another test tube.
- Take 5% NaOH solution and sample and check the solubility.
- Take 5% NaHCO3 and check the solubility.
- Take 5% HCl and observe the solubility.
- Take concentrated H2SO4 and sample and observe the solubility of the given sample.
Water solubility:
Place 0.05mL or 25 mg of compound in a small test tube and add 0.75 mL water in small portions. Shake test tube vigorously after the addition of each portion of solvent. If the compound is both water and ether soluble, the acid-base properties of the compound should be determined with litmus.
- litmus turn red-water soluble acidic compound
- litmus turn blue-water soluble basic basic compound.
- litmus neutral-water soluble general compound.
Results:
The solubility of given organic compound ___________________
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