Preliminary Test and Solubility Classification of Organic Compounds

Topics: Functional group, Carboxylic acid, Acetic acid Pages: 12 (3820 words) Published: January 25, 2012
Preliminary Test and Solubility Classification of Organic Compound

Keene Louise Topacio, Christopher Jay Robidillo

The experiment focuses on how to classify organic compounds by its functional groups. It is done by preliminary test and with the solubility test. Preliminary test used two known compounds also the unknowns. Physical state, color, odor, and ignition test were noted. The known compounds are inorganic and organic compounds. A comparison is made from the observation in the unknown sample, by which we had concluded that there were two organic compounds and one inorganic among the unknowns. In order to have a strong background about the solubility test, we first classify organic compounds of known functional group using the said test. Butyl bromide, ethanol sucrose, butyraldehyde, ethanoic acid, methyl amine, nitrophenol, diethyl ether, benzoic acid and propanone were used. It is found out that they are class X, Sn, S, N, Sa, Sb, S, N, A1 and Sn, respectively. We use water, ether, HCl, NaOH, NaHCO3, H2SO4, litmus paper, and phenolphthalein in classifying each compound based on their solubility and color change. It follows a certain scheme on testing the compound. Each test will link to another test until we ended up with the class of that compound. We finally determine the class of the three unknowns. It is found out to be an Sb - amine -, S -salt -, and an N -aromatic compound-. Keywords: solubility, classification, organic compounds, solubility test, preliminary test Introduction

One important part of experimental organic chemistry is to be able to analyze and identify an unknown organic compound from its functional groups. There are several steps in order to acquire this and there is no definite process. But there are systematic ways in different experimental organic chemistry books. For this experiment it will emphasize the preliminary examination and solubility characteristics of some known organic compounds and unknown samples.

Preliminary test is basically noting informations with lesser effort compared to the other tests the physical state, color, odor, and its ignition properties.
Physical state of a substance can make a distinction among organic compounds for the reason that at room temperature most of organic compounds are in its liquid state. This is due to the intermolecular forces of attraction in the compound.

The color is also informative because most pure organic compounds are white or colorless. Some discolorations of brown color are effect of oxidation reaction.
The odor of many organic compounds, especially the ones that have lower molar mass are highly distinctive. Also, functional groups have its' own different smell particularly alcohols, ketones, esters, aliphatic and aromatic hydrocarbons. Caution must be observed while smelling the unknown sample because large amounts of organic vapors should never be inhaled because of toxicity.

The ignition test involves a procedure in which a drop or two of a liquid or about 50-100 mg of a solid is heated gently on a crucible with a bunsen burner flame. Whether a solid melts at low temperature or only upon heating more strongly is then noted. The flammability and the nature of any flame from the sample are also recorded. A yellow, sooty flame is indicative of an aromatic or a highly unsaturated aliphatic compound; a yellow but non-sooty flame is characteristic of aliphatic hydrocarbons. The oxygen content of a substance makes its flame more colorless or blue; high oxygen content lowers or prevents flammability, as does halogen content. The unmistakable and unpleasant odor of sulfur dioxide indicates the presence of sulfur in the compound. If a white, nonvolatile residue is left after ignition, a drop of water is added and the resulting aqueous solution is tested with litmus or pHydrion paper; a metallic salt is indicated if the solution is alkaline.

Solubility of an organic compound in different solvents can present...

References: Baluyut John Y. G., De Castro Kathlia A., Organic Chemistry Laboratory for Chemical Engineering Students Part 2, 2004
Klein, David (2012). Organic Chemistry. Danvers. John Wiley & Sons, Inc.,
Gilbert, John. Experimental Organic Chemistry: A miniscale and Microscale Approach 5th Ed. Australia, Brooks/Cole Cengage Learning.
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