Properties and Reactions of Hydrocarbons Essay
Hydrocarbons are organic materials that contain only carbon and hydrogen atoms, these molecules can be saturated or unsaturated and acyclic, cyclic, or aromatic. In this experiment we used a variety of methods to examine the physical and chemical properties of hydrocarbons. The first experiment we tested a variety of solvents to see if they dissolved our alkane (Decalin). One would expect that non-polar solvents will dissolve alkanes because they are non polar as well 1. If the solvent did not dissolve in the alkane we heated the solution with a heat gun, because higher temperature increases solubility because energy in the form of heat can break bonds and allow for the molecules to join together. This is the reversed for a decrease in temperature the molecules move around less so there is less interaction between solute and solvent. We also differentiated alkanes and alkenes. Alkanes only contain c-c single bonds, are saturated, and are the least reactive. Alkenes are c=c double bonds, more reactive than alkanes, and unsaturated.
In the next part of the experiment we added bromine to alkenes. This caused an electrophilic halogenation reaction. If the bromine reacted with the alkene the bromine would discolor from orange and turn clear. Experiment Part A) Solubility of Alkanes: 1 mL of nine solvents (water, methanol, n-butanol, ethylene, glycol, acetone, hexane, toluene, ethyl acetate, and dichloromethane. ) was added to nine sample vials. Each vial then had 0. 5 mL of the alkane decalin added to each one. The mixtures were stirred to determine if the materials dissolved.
If the material was insoluble it was heated with an air gun to see if it would aid in dissolving the solution. This test helped us determine what kinds of solvents are useful for dissolving alkanes. Part B) Reactivity of Alkanes and Alkenes in Sulfuric Acid: 0. 5 mL of cyclohexane was added to one vial and 0. 5 mL of cyclohexene was added to another test vial. 0. 5 mL of concentrated sulfuric acid was then added to each vial, swirled, and observed. Part C) Bromine addition to alkenes: 1 mL of dichloromethane was added to five sample vials.
Next, about five drops, or 5-mm mound for dry agents of: cyclohexene, toluene, beta-pinene, camphene, and trans-stilbene was added to each individual tube and swirled. 4 drops of bromine solution was then added to each tube and observations were taken. (SITE) Results Table 1: Solubility of solvents tested with Decalin Solvent Solubility Water Insoluble Methanol Insoluble n-butynol Partially Ethylene glycol Insoluble Acetone Soluble Hexane Soluble Toluene Soluble Ethyl acetate Soluble Dichloromethane Soluble
Reactivity of alkanes and alkenes in sulfuric acid observations: 0. 5 mL Cyclohexane with addition of 5 mL concentrated sulfuric acid stayed clear 0. 5 mL Cyclohexene with addition of 5 mL concentrated sulfuric acid turned bright orange to black with heat and foul odor Table 2: Bromine Addition to Alkenes Test Chemical Reaction Cyclohexene Faint Yellow Toluene Orange Beta-pinene Clear Camphene Foggy white Trans-stilebene Foggy white precipitant All information came from 1 Discussion
The results from the solubility of alkanes was as follows: Water insoluble, methanol insoluble, n-butynol partially soluble, ethylene glycol insoluble, acetone soluble, toluene soluble, ethyl acetate soluble, dichloromethane soluble. For the insoluble solvents all were clear with a clear layer of separation, heating did nothing to these mixtures. n- butanol was partially soluble, but with the addition of heat this mixture was even more soluble. The non-polar solvents dissolved with the alkane as would be expected there was know separation layer and the solution was clear, because like dissolves like1.
For the Reactivity of alkenes and alkanes in sulfuric acid experiment the cyclohexane did not have a reaction it stayed clear. When the sulfuric acid was mixed with the cyclohexene there was a reaction; the solution turned black and began to smoke and smell fowl. This is because cyclohexene contains pi bonds which have more electrons and are more susceptible to electrophile attack which the Sulfuric acid is doing2. In the bromine addition to alkenes experiment the bromine reacted with the cyclohexene turned faint yellow, beta-pinene turned faint yellow, and camphene turned foggy white.
There was a partial reaction with trans-stilbene it was foggy white with a precipitant, time could have made this reaction be more pronounced because it would be able to mix better. There was no reaction with toluene it stayed orange. When the alkenes reacted with the bromine the double bond breaks and a bromine atom becomes attached to each carbon the bromine loses its orange color and becomes a colorless liquid this is known as electrophilic addition3. No errors were occurred while performing this experiment, additional drops of bromine to the Addition of bromine to alkenes experiment might help in making the experiment more pronounced.
 Setzer, M. C. ; Setzer, W. N. Organic Chemistry Laboratory Manual Cengage Learning: Ohio,2004  Clark Jim. (2000). Retrieved February 7, 2010, from http://www. chemguide. co. uk/mechanisms/eladd/symbr2. html  University of Michigan. (2010). Retrieved February 9, 2011, from http://www2. chemistry. msu. edu/faculty/reusch/VirtTxtJml/addene1. htm