Hydrocarbons

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  • Topic: Benzene, Hydrocarbon, Alkane
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  • Published : December 15, 2012
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Analysis of Hydrocarbons

Jovellanos, Bien Jindrich Johannes; Lacson, Danise Angelica; *Lagula, Nina Francesca; Lañez, Kristine

Department of Psychology
College of Science
University of Santo Tomas
España Manila 1015

Abstract
A hydrocarbon is strictly composed of carbon and hydrogen atoms only. Five hydrocarbons were used namely hexane, cyclohexene, toluene, naphthalene (in hexane), and the unknown (which will be known through parallel chemical tests). Three tests, nitration test, bromine test and basic oxidation test were conducted to fully differentiate each type of hydrocarbon from one another. Nitration tests resulted to three positive outcomes and two negative outcomes. A positive outcome in the nitration test shows that the hydrocarbon is aromatic while a negative outcome is aliphatic. In the bromine test, the results showed that there is one saturated aliphatic while the other is unsaturated aliphatic. In the last test (basic oxidation test), all five hydrocarbons resulted to positive products. Through the comparison of results of each hydrocarbon from each test, the unknown was observed to be Toluene.

Introduction
Hydrocarbons can probably be considered as the most important class of organic compounds. It is mainly composed of carbon atoms and hydrogen atoms only. Most hydrocarbons are colorless and odorless. It is divided into two categories, aliphatic and aromatic. Aliphatic hydrocarbons have the principal carbon atoms arranged in chains. It can be saturated (wherein carbon-to-carbon bonds are single bonds) or unsaturated (wherein there are one or more carbon-to-carbon multiple bonds). Saturated aliphatic hydrocarbons are alkanes while unsaturated aliphatic hydrocarbons are alkenes and alkynes. The general formula of alkanes, alkenes and alkynes are CnH2n+2, CnH2n, and CnH2n-2, respectively. Alkanes, alkenes and alkynes can be open-chain (acyclic), cyclic, unbranched or branched. Aromatic hydrocarbons are represented by a six-carbon ring. Its difference with cyclic is that it is composed of three double bonds. It can be alkyl-chained or not. Benzene, C6H6, is said to be the most common aromatic hydrocarbon. The hydrocarbons, hexane, cyclohexene, toluene, naphthalene (in hexane) and the unknown (which is toluene) were analyzed in the experiment. Hexane and cyclohexene are aliphatic (saturated) while toluene and naphthalene are aromatic.

Hexane is a six-carbon alkane hydrocarbon. Its molecular formula is C6H14. It is colorless and odorless. It is non-polar so it is often used as a solvent.
Cyclohexene is a six-carbon ring alkane hydrocarbon. Its molecular formula is C6H12. Its only difference with hexane is that it is in a cyclic form with double bonds while hexane is in a linear form with single bonds only. Also, its hydrogen atoms are two less than that from a hexane’s hydrogen atoms. It is colorless and odorless. It is also used as a solvent because of its non-polarity. Toluene is an aromatic hydrocarbon. Its molecular formula is C6H5CH3. It is related to benzene. It is colorless and has an odor similar to that of a pentel pen’s. It is mostly used as a raw material to produce other chemicals. Benzoic acid is an example that is produced from toluene. Naphthalene is a polycyclic aromatic hydrocarbon. Its molecular formula is C10H8. It is composed of two benzene rings fused together. It is colorless and has an odor close to that of mothballs. It is usually found in crude oils.

Figure 1: Cyclohexane structure Figure 2: Toluene structure Figure 3: Naphthalene structure

These four hydrocarbons have similarities and differences so different tests are conducted to fully differentiate one from the other. Color and miscibility were the common basis of a hydrocarbon’s properties. Nitration test was conducted to test the aromaticity of the compound. Aromaticity of the compound is determined when a yellow...
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