CLASSIFICATION TESTS FOR HYDROCARBONS Richelle Madrigal, Brigida Moran , Mikaela Naui, Loudette Negado, Ann Rodriguez Group 7, 2FPH, Faculty of Pharmacy, University of Santo Tomas
Abstract
Hydrocarbons are organic compounds, which contain only carbon and hydrogen. We used different physical and chem tests to determine the physical properties and chemical properties in terms of structure and behavior. We were able determine if the hydrocarbon is saturated, unsaturated, aromatic or an arene. In this experiment, we used hexane, heptane, cyclohexane, benzene and toluene as our sample compounds in determining whether they are hydrocarbons not. In determining the classification of the sample compounds we observed their physical state, performed the ignit test, Baeyer’s Test and the Bromine Test, tested the aromaticity by using the method of nitration, and we tested its oxidation by means of basic oxidation.
Introduction
hexane are mostly non-reactive, and are frequently used as solvents in organic Hydrocarbons are the simplest organic reactions because they are very non-polar. It is compounds. Containing only carbon and a very important constituent in gasoline and is hydrogen, they can be straight chain, branched also used in food processing. chain, or cyclic molecules. Carbon tends to form four bonds in a tetrahedral geometry. Hydrocarbon derivatives are formed when there is a substitution of a functional group at one or more of these positions. Hydrocarbons Fig. 2 (Structure of Hexane) can be divided into two groups: saturated hydrocarbons and unsaturated hydrocarbons. Cyclohexane is a cycloalkane with the Saturated hydrocarbons are composed entirely molecular formula C 6 H 12 , has a molar mass of 84.160 g/mol, and boiling point of 80.74°C. It is of single bonds and are saturated with used as a non-polar solvent and a raw material hydrogen while unsaturated hydrocarbons for the production of adipic acid and have one or more double or triple bonds caprolactam used for nylon production. between carbon atoms. Those with double bond are called alkenes.
Fig. 3 (Structure of Cyclohexane)
Fig. 1 (Classification of Hydrocarbons)
Hexane alkane hydrocarbon with a chemical formula of C 6H 14 , has a molar mass of 86.18 g/mol, and a boiling point of 69°C. Isomers of
Benzene has a molecular formula of C 6H 6; molar mass of 78.11g/mol, and a boiling point of 80.1°C.It is a colorless, highly flammable liquid with a sweet smell. It is a known carcinogen, therefore its role as an additive in gasoline is now limited it is widely used in the production of drugs, synthetic plastic and dyes.
The solvent used in this experiment is concentrated H 2SO 4. The measurement of flammability is determined through the use of the Ignition test. Many compounds are Fig. 4 (Structure of Benzene) determined by the characteristics of their flame when they burn. Aromatic hydrocarbons burn Toluene is an aromatic hydrocarbon with a molecular formula of C 7H 8, has a molar mass of with a yellow, sooty flame due to high carbon 92.14 g/mol, and a boiling point of 110.6°C. amount, while aliphatic hydrocarbons burn with Toluene reacts as a normal aromatic yellow, but less sooty flames. Baeyer’s Test is hydrocarbon towards electrophilic aromatic used to test the presence of unsaturation substitution. (double bonds). A similar test can be done with the use of Bromine (Bromine Test), Baeyer’s Test uses potassium permanganate which makes it turn pinkish to brown when reacting with double or triple bonded organic material. Aromaticity is the special stability of the planar, cyclic, fully conjugated molecules with 4n + 2 Fig. 5 (Structure of Toluene) electrons. Such molecules have orbital systems with all bonding molecular orbitals Heptane is the straight-chain alkane with the chemical formula C 7H 16, has a molar mass completely filled with all anti- bonding and nonof 100.21 g/mol and a boiling point of 98.42 °C. bonding orbitals empty. The criterion for a It is used as test fuel component in anti-knock compound to be aromatic is Hückel’s Rule test engines. wherein the number of depolarized electrons in an aromatic ring is equal to 4n +2 where n is zero or any postivie interger. Fig. 6 (Structure of Heptane)
These are the following sample compounds that were tested for the classification of hydrocarbons. OBJECTIVES is to be able to differentiate hydrocarbons in terms of intrinsic physical properties and chemical properties in terms of structure and behavior and to analyze a hydrocarbon and determine if it is saturated, actively unsaturated, aromatic or an arene. Materials and Methods
The following methods of testing were used; observation of the physical state, Solubility in concentrated H 2SO 4, Ignition Test, Baeyer’s Test, Bromine Test, Nitration and Basic Oxidation. The solubility is determined by the
PROCEDURES: Taking note of the physical
state and color of the sample compounds by observing it through the testube, the odor was obtained by wafting the testube to smell.
Solubility was tested by adding 1mL of concentrated H 2SO 4 to the sample compounds. The Ignition Test was performed wherein 3-5 drops of the liquid sample was placed on an evaporating dish and lit with a match. Tests for active unsaturation required us to use the Baeyer’s Test and the Bromine Test. The Baeyer’s Test had KMnO 4 dropped in a test tube with 5 drops of the liquid sample and was shaken vigorously, decolorization was observed. The Bromine Test had the same procedure but instead of using KMnO 4 we used 10 drops 0.5% Br 2 in CCl4 reagent and
observed the decolorization. We applied the litmus test afterwards. 2 ml concentrated HNO 3 was placed in an Erlenmeyer flask. The flask was immersed in an evaporating dish containing water and 2 ml of concentrated H 2SO 4 was added gradually. The resulting mixture (nitrating mixture) was cooled in room temperature. 8 drops of the nitrating mixture was added to 5 drops of the sample in a dry test tube. The test tube was shaken to ensure complete mixing. The formation of a yellow oily layer or droplet was noted, and then it was diluted with 20 drops of water. If there was no apparent reaction observed within a minute, the test tube was placed in a water bath (50°C) for 10 minutes. It was diluted with 20 drops of water and the results were noted down. We added 8 drops of 2% KMnO 4 solution and 3 drops of 10% NaOH solution were added to 4 drops of the sample in a test tube. Each test tube was subjected to a water bath for 2 minutes. Any color change and formation of brown precipitate was observed and noted down. Results and Discussions
After subjecting all 5 organic samples to different physical and chemical tests, it was observed that all 5 organic samples were flammable and immiscible in concentrated H 2SO 4. All except hexane and heptane produced soot when ignited. Only cyclohexene behaved as an actively unsaturated hydrocarbon. All were aromatic compounds except cyclohexane and cyclohexene. The only compound oxidized was cyclohexene. Refrences 1. Heasley. (1991). 2. 3.
Chemistry and Life in the Laboratory, ed. Prentice Hall: New Jersey, USA
Singh. (1995). Microscale and Selected Macroscale Experiments for General and Advanced Chemistry, ed. John Wiley and Sons: New York City, USA Shri
(2004)
he Systemati
de tifi ati
f
Organic Compounds, ed. John Wiley and Sons: New York City, USA 4. http://www.scribd.com/doc/25377353/ClassificationTests-for-Hydrocarbons
