Comparative Investigation of Organic Compounds Essay

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Comparative Investigation of Organic Compounds


Organic compunds were examined to a comparative investigation to differentiate the properties of each sample. The physical state at room temperature, odor and color of the sample were noted by simple observation. In terms of solubility in H2O, 5% NaOH solution and 5% HCl solution, the samples were classified as to miscible, slightly immiscible or immiscible for liquid; and very soluble, soluble, partially soluble or insolubse for solid. The samples also underwent a test using litmus paper to classify its acidity, basicity or neutrality. The next procedure was the ignition test, which classified the sample as to whether the sample was flammable, or non-flammable and the color of the flame were noted. After going through all the tests, it was proven that organic compounds possess different properties.


Organic compounds are the complex compounds of carbon. Because carbon atoms bond to one another easily, the basis of most organic compounds is comprised of carbon chains that vary in length and shape. Hydrogen, nitrogen, and oxygen atoms are the most common atoms that are generally attached to the carbon atoms. Each carbon atom has 4 as its valence number which increases the complexity of the compounds that are formed. Since carbon atoms are able to create double and triple bonds with other atoms, it further also raises the likelihood for variation in the molecular make-up of organic compounds. [1] Carbon can also bond with itself and hydrogen to form both chains and rings called hydrocarbons. Because the covalent bond between carbon and hydrogen is nonpolar, these carbon skeletons are hydrophobic. Functional groups can be added to carbon skeletons to make them more hydrophilic. Differences in the carbon skeleton and attached functional groups cause organic molecules to have different chemical properties.

The chemical properties of a molecule determine how it interacts with other molecules and the role the molecule plays in the cell. Some functional groups are hydrophobic and others are hydrophilic. [2] Hydrocarbons are the simplest class of organic compounds and are composed solely of hydrogen and carbon. This class can be further divided into two groups: aliphatic hydrocarbons and aromatic hydrocarbons. Aliphatic hydrocarbons can be classified based on the structure and bonding of the carbon skeleton into three groups: alkanes, alkenes, and alkynes. Aromatic hydrocarbons or arenes, which contain a benzene ring, were originally named for their pleasant odors. These compounds possess special properties due to the delocalized electron density in benzene, including additional stabilization due to the system of conjugated rings consisting of unsaturated bonds, lone pairs, and empty orbitals. [3] Organic compounds have different properties. They may vary in their physical state at room temperature, color, odor and solubility in different reagents. The experiment aims to differentiate organic compounds in terms of: certain intrinsic physical properties, solubility in different solvents and behavior towards ignition. [4]


Compounds Tested

Benzoic Acid
Ethyl acetate
Ethyl amine

Figure 1. Samples used in the experiment

Physical State, Color and Odor
The physical state of the sample was observed at room temperature. Then, the color was noted and with a wafting motion, the odor was described.

Solubility Properties
The sample was introduced in a clean and dry test tube. 4 drops of each sample was added if the sample is a liquid; and 0.1 g of sample was added if the sample is a solid. The solid samples were grinded to increase the surface area. The solvent was added drop wise and counted the number of drops of solvent added to a total of 3mL. Any change, warming effects, soluble/insoluble, miscible/ immiscible or effervescence was noted. Reaction with Litmus Paper

If the water is soluble in water, the aqueous solution was tested with red and blue litmus paper. The color changes in both litmus paper was noted. Ignition Test
Three to five drops of the liquid sample was placed in a small evaporating dish and then was lighted with a match. If the sample is solid, a pinch amount was used. The sample was observed if it is flammable or not. The color of flame produced was noted. Results and Discussions

A. Observation of Physical State at Room Temperature, Color and Odor of Samples

Table 1. Intrinsic properties of samples

As shown in the table, most of the hydrocarbons are clear. The result of the experiment showed that Phenol becomes red upon oxidation and white crystals for benzoic acid. The odors of the compounds are quite similar to each other but still have different identity. Cyclohexane and DCM both have paste-like odor. Ethanol smells like alcohol while benzoic acid is odorless. Ethyl acetate has plastic balloon odor while ethylamine has urine odor or can be ammoniacal odor because of its functional group, amine.

B. Test for Solubility Properties of Sample in H2O, 5% NaOH solution and 5% HCl solution

Table 2. Solubility of sample in different solvents

The solubility properties of organic compounds using H2O, 5% NaOH solution and 5% HCL solution indicates whether the solid sample is soluble or insoluble and if the liquid sample is miscible and immiscible. Solubility of sample to the solvent is related to polarity of the two substances and the intermolecular forces of attraction during the solution process. The “like dissolves like” principle is involved. Water is a polar solvent so the sample that is soluble or miscible with water is also polar. Based on the results, ethanol, phenol, ethyl acetate and ethylamine are polar compounds. The solubility in 5% NaOH solution of a water insoluble sample is an indication that acidic functional group is present. Compounds that behave as bases in aqueous solution are detected by their solubility in 5% HCl solution. [5]

Ethanol and phenol are miscible while benzoic acid is very soluble in 5% NaOH solution. The rest of samples are immiscible. Ethanol and ethylamine are miscible in 5% HCl solution while the rest of the samples are immiscible and benzoic acid is insoluble. C. Reaction with Litmus Paper

Table 3. Acidity, basicity and neutrality of samples
Reaction with litmus paper indicated acidity, basicity or neutrality of water-soluble samples. Acidic solution turns blue litmus paper to red and red litmus paper to red. Blue litmus paper to blue and red litmus paper to blue indicates a basic solution. Neutral solution is characterized by blue to blue litmus paper and red to red litmus paper.

As shown in the table, phenol and ethyl acetate are acidic while ethylamine is basic. Ethanol is a neutral sample. Cyclohexane, DCM and benzoic acid were not subjected to the litmus paper test because of their immiscible property with water. D. Ignition Test

Table 4. Degree of Luminosity of the Samples

The result of the Ignition test indicates the presence of unsaturated or high carbon to hydrogen ratio. The degree of luminosity can be assessed by the presence of yellow or luminous flame. The aromatic compounds burn with sooty flame due to the incomplete combustion, which causes the formation of an unburned carbon. The higher the number of Carbon atoms, the higher the
degree of luminosity. In addition, the higher the Carbon: Hydrogen Ratio, the higher the degree of luminosity. In terms of degree of luminosity: aromatic compound > unsaturated hydrocarbon > saturated hydrocarbon. [6] Complete combustion is indicated by a blue flame (non-luminous) and there is more heat than light, the carbon is completely oxidized. 2C10H22 +31O2  20CO2 +22H2O

Incomplete combustion is indicated by a yellow flame (luminous) and there is much light than heat; the carbon is not completely oxidized. 2C2H2 + 5O2  4CO2 + 2H2O + heat
Based on the table, cyclohexane, phenol, ethyl acetate and ethylamine are flammable with luminous flame while ethanol with non-luminous flame. DCM and benzoic acid are both non-flammable


[1] retrieved on September 2, 2013 from [2] retrieved on September 2, 2013 from [3] retrieved on September 2, 2013 from–2/introduction-to-hydrocarbons/ [4] Bayquen, A., Cruz, C., de Guia, R., Lampa, F., Peña, G., Sarile, A., & Torres, P. (2009). Laboratory Manual in Organic Chemistry. Quezon City: C&E Publishing, Inc..

[5] Retrieved on September 2, 2013 from

[6] Shriner, R., Hermann, C.K.F., Morrill, Curtin, D.Y. (1998) The Systematic Identification of Organic Compounds. 7th ed. New York: John Wiley & Sons, Inc.

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