Solubility Behavior of Organic Compounds

SOLUBILITY BEHAVIOR OF ORGANIC COMPOUNDS

Avelino, K.1, Maramba, C. N.2, Morante, M.3, Pablo, C.H.4

1Department of Biology, College of Science, University of the Philippines Baguio

December 6, 2012

ABSTRACT

The objectives of the experiment are to relate the organic compounds' structures to their solubility and to classify the organic compounds as water soluble (S1), ether soluble (S2), strong acid (A1), weak acid (A2), base (B), neutral (N), miscellaneous neutral (M), and inert (I). The solubility of each compound was tested in 1mL of water, and then compounds that resulted as soluble were further tested in ether and for those which are insoluble were tested in 5% NaOH. Thus, soluble compounds were tested in 5% NaHCO3 and insoluble compounds with 5% HCL. Lastly, insoluble test compounds were tested in concentrated H2SO4. Compounds that manifested reactions such as change in color, production of heat, formation of precipitate, or evolution of gas in the said reaction were recorded as soluble. Benzamide and aniline were insoluble to water, NaOH and HCl, but were soluble in H2SO4 and were labeled as neutral compounds. Benzaldehyde, toluene, and hexane are S2 or compounds soluble in water; Benzyl alcohol, ethanol, phenol, sucrose, and acetone on the other hand were S1 which were only soluble in water and not in ether. Benzoic acid was insoluble in water but soluble in NaOH. The experiment was successful because the solubility of all the test compounds in the given solvents were determined and further classified.

INTRODUCTION

One important property that organic compounds exhibit is that their structure is related to their solubility. Solubility is the amount of a substance that will dissolve in a given amount of another substance and is typically expressed as the number of parts by weight dissolved by 100 parts of solvent at a specified temperature and pressure or as percent by weight or by volume. The general rule used in determining whether a solute is soluble or insoluble in a given solvent is "like dissolves like" where nonpolar solutes dissolve in nonpolar solvents; polar solutes dissolve in polar solvents or chemical reactions may occur between the solvent and the solute causing dissolution.

Compounds that are branch-chained are more soluble than the corresponding straight-chained compound. Branching lowers intermolecular forces and decreases intermolecular attraction. The position of the functional group in the carbon chain also affects solubility.

The solubility of organic compounds in organic solvents should be determined in order to plan for a variety of laboratory operations which include choosing solvents for organic reactions, dissolving substrates for spectral analyses, cleaning glassware, extraction, thin layer and other chromatography and crystallization.

The objectives of the experiment are to relate the organic compounds' structures to their solubility and to classify the organic compounds as water soluble (S1), ether soluble (S2), strong acid (A1), weak acid (A2), base (B), neutral (N), miscellaneous neutral (M), and inert (I).

RESULTS

Compound Solvents Solubility Class

H2O Ether 5% NaOH 5% NaHCO3 5% HCl 5% H2SO4

Hexane Soluble Soluble S1

Benzamide Insoluble Insoluble Insoluble Soluble Neutral

Acetone Soluble Insoluble Soluble S2

Ethanol Soluble Insoluble Soluble S2

Benzyl Alcohol Soluble Insoluble Soluble S2

Aniline Insoluble Insoluble Insoluble Soluble Neutral

Toluene Soluble Soluble S1

Sucrose Soluble Insoluble Soluble S2

Benzaldehyde Soluble Soluble S1

Benzoic Acid Insoluble Soluble Soluble A1

Phenol Soluble Insoluble Soluble S2

DISCUSSION

The table above shows the solubility of each organic compound in different types of solvents, the table also shows the solubility class of the given organic compounds. Some of them including benzamide, and aniline were insoluble to water, NaOH and HCl, but they were soluble in H2SO4 so they were labeled as Neutral compounds, they are compounds which are water- fearing or hydrophobic which makes them insoluble to water but are soluble to other organic solvents. Benzaldehyde, toluene, and hexane are S2 or compounds soluble in water; Benzyl alcohol, ethanol, phenol, sucrose, and acetone on the other hand is S1 which is only soluble in water and not in ether. Benzoic acid is labeled as A1 which is insoluble in water but soluble in NaOH.

CONCLUSION

Benzamide and aniline were insoluble to