Hydrocarbon Lab

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Virginia Commonwealth University *

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Chemistry

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Dec 6, 2023

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Hydrocarbon Lab 6/9/21 Dr. Hayes Hannah Aldridge Introduction Hydrocarbons are nonpolar organic compounds which contain only carbon and hydrogen. They are classified depending on structure and how many carbon bonds there are. Hydrocarbons can contain single, double, or triple bonds. Single bonds are alkane, double bonds are alkene, and triple bonds are alkyne. Carbons can also be linked in a closed cycle containing a benzene rings. These cyclic hydrocarbons are called aromatics. Below in figures 1 – 3 are examples of alkane, alkene, and an aromatic, respectively. Figure 1: Figure 2: Figure 3: Some hydrocarbons are saturated and others are unsaturated. What this means is that, in an unsaturated hydrocarbon, there is at least one carbon-carbon double or triple bond. In a saturated hydrocarbon, this is primarily composed of carbon-carbon and carbon-hydrogen single bonds. Alkanes are typically the saturated hydrocarbons while all other types are unsaturated. Saturated hydrocarbons are at max capacity for hydrogen present with given amounts of carbon in a compound, thus, one cannot add more hydrogen. Acyclic alkanes are saturated. Figures 4 and 5 will depict a catalyst of hydrogen being added to unsaturated compounds with the results of a saturated compound. Figure 4: Figure 5: Some of the physical properties observed in hydrocarbons its immiscibility with polar solvents is due to their hydrocarbons resulting from non-polar characters of compounds. They will, however, mix with relatively non-polar solvents like ligroin (a mix of alkenes), carbon tetrachloride ( CC l 4 ) or dichlormethane ( C H 2 C l 2 ¿ . Most hydrocarbons float in water because of their density being less than that of water. Hydrocarbons are molecules that have little to no electronegative atoms. Therefore, they are soluble in low polarity solvents but not water because water is extremely polar. Chemical reactivity of hydrocarbons are determined by the type of bond in the compound. Saturated hydrocarbons burn though they are typically unreactive to most reagents. These alkanes do undergo substitution reactions with halogens but have to have an activation by ultraviolet light for reactions to begin. Unsaturated hydrocarbons (alkenes and alkynes) burn as well as react to the addition of reagents to double or triple bonds.
In combustion the major component in ‘natural gas’ is the hydrocarbon methane. Other hydrocarbons used for heating are propane and butane. The products from combustion are carbon dioxide and water with heat being evolved. In the figures below will be two examples of combustion equations. Figure 6: C H 4 + 2 O 2 →C O 2 + 2 H 2 O + Heat Figure 7: C H 3 C H 2 C H 3 + 5 O 2 3 C O 2 + 4 H 2 O + Heat In reactions with bromine, unsaturated hydrocarbons react quickly with bromine in solutions such as carbon tetrachloride or cyclohexane. The reaction is the addition of bromine elements to the multiple carbon bonds. Alkenes will react with bromine in solutions producing an alkyl bromide. The normal yellow/orange color of bromine will disappear as it reacts with the alkenes. Single carbon bonds have no reaction. See below, figures 8, to see examples of bromine being added to alkenes. Figure 8: However, aromatic compounds resist the addition reaction because of their aromaticity, or their closed loop of electrons. These instead need a catalyst in order to react with bromine, a catalyst such as iron or aluminum chloride. As seen below, an example. Substitutions take place and produces gasses such as HBr. Figure 9: In reactions with concentrated sulfuric acid, alkenes react with cold concentrated sulfuric acid by addition. Alkyl sulfuric acids for as a byproduct and is easily dissolved in H 2 SO 4 . Figure 10:
Saturated hydrocarbons are unreactive. Alkynes react slowly and need a catalyst, and aromatic compounds are unreactive as well. The purpose of this lab was to investigate the physical properties, solubility, and density of heptane, cyclohexane, 1-hexyne, and toluene as well as determining the nature of three unknowns. Table of physical constants : Table 1 Name Formula Mass Mp (C ° ) Bp (C ° ) Density(kg/ m 3 ¿ Heptane C 7 H 16 100.21g/mo l -90.55 98.42 684 Cyclohexane C 6 H 12 84.16 g/mol 7.00 80.74 779 1-hexyne C 6 H 10 82.14 g/mol -132.00 71.00 730 Toluene C 7 H 8 92.14 g/mol -95.00 110.60 867 Sulfuric acid H 2 SO 4 98.08 g/mol 10.00 337.00 1830 Potassium Permanganat e KMnO 4 158.03 g/mol 240.00 100.00 2700 Hydrochloric acid HCl 36.46 g/mol -114.20 -85.05 1.49 Water H 2 O 18.02 g/mol 0 100 997 Acetone C 3 H 6 O 58.08 g/mol -95.00 56.00 784 Mineral water 82.2 g/mol -73.00 90-140 6560 The materials used : 1. Heptane (alkane); LOT- 071053 2. Cyclohexene (alkene); LOT- 3AHJ17X025, Exp: AUG/15 3. 1-Hexyne (alkyne); LOT- 10203927 4. Toluene (aromatic); LOT- 207986 5. Sulfuric acid 6. Potassium permanganate 7. Hydrochloric acid 8. Water 9. Mineral water 10. Acetone 11. 42 10x75mm test tubes 12. Pipettes 13. Unknown substances A-C Procedure: A) Each test tube was labeled with the respective hydrocarbon names and unknowns. There was six test tubes of heptane, cyclohexane, 1-hexyne, toluene, unknown A, unknown B, and unknown C that had a total of forty two test tubes. Each test tube had ten drops of each hydrocarbon and unknown. Sulfuric acid, potassium permanganate, hydrochloric acid, water, ligroin, and acetone were added respectfully to tubes one through six. This step was repeated for all except sulfuric acid for each set or hydrocarbons and unknowns. Each test tube was filled and stirred by holding the neck of the test tube and striking the bottom o the tube gently several times. It was then allowed to rest for a minute to determine the miscibility and any color changes were noted along with any exothermic reactions.
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