Vanessa P. Manibpel
De La Salle University - Dasmariñas
Five substances namely Hexane, Eugenol, Unknown hydrocarbon 1, Unknown hydrocarbon 2, and Acetylene gas was used for the selective reactivity of hydrocarbons to functional group tests; Bayer’s test, Bromine test light, Bromine test dark, and Tollen’s test. In Bayer’s test, only Acetylene, Eugenol and Unknown hydrocarbon 2 reacted positively and the rest retain the purplish color of KMnO4. On the other hand, the five compounds in Bromine test with light reacted positively. In Bromine test dark, Hexane and Unknown hydrocarbon 1 did not react because light (UV) is absent. Lastly, in Tollen’s reagent, only Acetylene reacted positively and all the other compounds gave a negative result since they are all hydrocarbons.
Hydrocarbons are simple organic compounds with a distinct character of having Carbon and Hydrogen atoms only. They are divided into three main categories base on the type of orbital hybridization they have. The three main groups of Hydrocarbons are Alkanes, Alkenes, and Alkynes (1). Alkanes are sp3-hybridized hydrocarbons characterized by single bonds between carbon atoms included in their chains. Alkanes are also called saturated hydrocarbons because they contain the highest possible H atoms that they can since their single bonds give the Carbon atoms the opportunity to bond with three or two hydrogen atoms. Alkenes on the other hand are sp2-hybridized substances that are distinguished from other hydrocarbons through the presence of double bond/s between its carbon atoms. The third category of hydrocarbons is sp-hybridized Alkynes that have triple bond/s between C atoms. Alkenes and Alkynes, as contrasted to Alkanes, are classified as unsaturated hydrocarbons (1). In the real world, these single, double, and triple bonding are non-observable since they exist in the molecular level. The answer to identification of hydrocarbons based on their C atom bonding is the application of functional group tests. These tests utilize active reagents that react with hydrocarbons and gives indicators that are primarily color changes in order to signify that a certain hydrocarbon is a saturated hydrocarbon or an unsaturated one. For hydrocarbons, the level of saturation is determined by using Bayer’s reagent or Bromine test. Bayer’s reactant is an alkaline solution of Potassium permanganate which is considered as a strong oxidizing agent. It will react with triple or double bonded Carbons in order to change the violet color of solution to brown. Tollen’s test on the other hand, is used to identify if a compound is an aldehyde or a ketone. In the experimentation, the three aforementioned tests were tested on the experiment It was assumed that the compounds will react with their corresponding functional group test and therefore the correct reaction mechanism will be established and seen. Furthermore, it was also theorized that through the utilization of the prior tests, the two unknown hydrocarbons will be classified as an alkane, alkene, or alkyne.
MATERIALS AND METHODS
The experimentation was divided into two parts. The first duration dealt with the reaction of four hydrocarbons with different reagents used for the functional group tests that were conducted. 5 drops of Hexane, Eugenol, Unknown hydrocarbon 1, and Unknown hydrocarbon 2 were separately placed in 4 dry clean test tubes one at a time (16 test tubes for all the compounds tested). Each compound was added with Bayer’s reagent, Bromine in Carbon tetrachloride (light and dark), and Tollen’s reagent. The reaction of the four organic compounds was observed and noted down (3). On the second duration of the activity, acetylene, an alkyne, was tested for its reactivity in the previous functional group tests conducted. Four dry clean test tubes with cork were procured. The four reagents used were placed inside these test tubes and was allowed to react with...