Properties of Hydrocarbons Essay

Custom Student Mr. Teacher ENG 1001-04 17 November 2017

Properties of Hydrocarbons

Aim: To demonstrate that different classes of organic molecules undergo different characteristic reactions.

Data Collection:

Cyclohexane

Toluene

Cyclohexene

Combustion

– no sootiness

– calm, bright flame

– short burn

– a lot of sootiness

– strong, bright flame

– long burn

– medium sootiness

– bright flame

– short burn

Solubility in distilled water

– not very soluble

– less dense than water

– bubbles formed

– not very soluble

– less dense than water

– bubbles formed

– not very soluble

– less dense than water

– bubbles formed

Solubility in dichloromethane

– soluble

– soluble

– mostly soluble

Density

0.79 g/ 1 cm�

= 0.79 g/cm�

Actual: 0.7785 g/cm�

0.86 g/ 1 cm�

= 0.86 g/cm�

Actual: 0.8669 g/cm�

0.87 g/ 1 cm�

= 0.87 g/cm�

Actual: 0.81 g/cm�

Potassium permanganate

– immiscible

-immiscible

-immiscible

– light brown precipitate formed

Bromination

– colorless layers

– insoluble

– denser than bromine

– forms layers

– light orange color below, dark color above

– insoluble

– insoluble

– denser than bromine

– light orange color

Addition of Sulfuric acid

– no reaction

– clear mixture

– no reaction

– bubblish layer on top

– dark orange mixture formed

Conclusions and Evaluation:

The combustion experiment tested how well the hydrocarbons burned. Each of the compounds was put in a watch glass and burned. Cyclohexane was the cleanest burner because it had the least sootiness while also maintaining a bright flame. Toluene had the most sootiness and also had a very bright flame. It was difficult to identify the most efficient burner because different amounts of each compound were put in the watch glass causing them to burn for different times. However, I believe that although toluene was used at a greater quantity than the other two compounds, it would have burnt for the longest time if equal amounts were used.

Cyclohexane, toluene and cyclohexene represented saturated, aromatic and unsaturated hydrocarbons respectively. The solubility test showed that all the types of hydrocarbons used are not soluble in water and are less dense than water because when I shook the mixtures, all the hydrocarbons settled on the upper of the two layers that were visible. I believe that the hydrocarbons were not soluble in water because the van der Waal’s forces that exist between its molecules are not strong enough to break the hydrogen bonding in water, which causes the two layers to form.

The solubility test in dichloromethane showed that the hydrocarbons used are soluble in organic solvents. Dichloromethane is an organic solvent and van der Waal’s forces exist between its molecules. Since all the hydrocarbons were soluble in dichloromethane, it shows that the van der Waal’s forces in the hydrocarbons were able to replace the van der Waal’s forces that exist between the molecules in dichloromethane, therefore solubility was possible. The solubility results achieved are very accurate as justified by the following statement, “Alkanes are virtually insoluble in water, but dissolve in organic solvents. Alkenes are virtually insoluble in water, but dissolve in organic solvents.” (An introduction to alkanes and cycloalkanes, an introduction to alkenes)

The density was calculated by calculating the mass of 1 cm� of each hydrocarbon. The density values were very accurate relative to the actual values for density for the hydrocarbons. The values for cyclohexane and toluene show that accurate equipment was used such as a measuring cylinder and an electronic balance. However, the value for cyclohexene shows that some human error did exist because it was slightly inaccurate relative to the values achieved for the other hydrocarbons.

Cyclohexane and toluene had no reactions with potassium permanganate as the substances did not mix. Cyclohexene, on the other hand, did not mix with potassium permanganate but formed a light brown precipitate suggesting that a small reaction did occur.

All the hydrocarbons were insoluble in bromine water. All of the mixtures from layers, sometimes different colored to the original color of the mixtures. This shows that a small reaction did occur between toluene and bromine water as well as cyclohexene and bromine water. Cyclohexane produced no color change as both the substances remained colorless.

Cyclohexane and toluene did not react with sulfuric acid. Cyclohexene produced a dark orange color suggesting that a reaction took place. This reaction is good for separating alkenes and alkanes because alkanes do not undergo a reaction with sulfuric acid while the reaction of alkenes with sulfuric acid is very visible.

The results achieved above show that saturated and unsaturated hydrocarbons have a large difference in their properties, even if they originate from the same skeleton. For example, cyclohexane and cyclohexene both originate from six carbon atoms but the added double bond in the cyclohexene differ the properties between the two significantly.

The results described above are very accurate, as proved by the justifications on the density values as well as the solubility tests. Accurate equipment such as a measuring cylinder and an electronic balance helped me achieve my goal of distinguishing between saturated, unsaturated and aromatic hydrocarbons. However, human error was still part of the experiment as clearly seen through the density test for cyclohexene. The other two density values were very accurate but the cyclohexene was slightly off the actual value. However, this was the only inaccuracy throughout the experiment as all the other results were proved using reliable sources on the internet.

Since this lab mostly involved qualitative tests, quantitative measurements were not vital and therefore there was little need for measurements which would have determined accuracy. However, in the combustion test, equal measurements of the substances could have been used to observe the length of each substance’s burn. This was impossible to identify because of the large amount used for toluene which meant that it burned for a very long time. The use of corks and test tubes for the solubility tests and other reactions ensured that the mixing was efficient and good observations were able to be made. Safety precautions were also taken throughout the experiment.

These factors all show that the experiment was successful as it provided correct results, justified by reliable sources on the internet. Although the experiment was a success, I could have been more focused when carrying out the experiments and the density values I obtained could have been more accurate. In addition, the large amount of toluene that was used would not have occurred and it would have been easy to identify the most efficient burner. Further research can possibly be done on the amount of energy for each substance during combustion to identify the most useful substance for burning and chemical equations could have been written to observe the products in the reactions that occurred.

Works Cited

Clark, Jim. “An introduction to alkenes.” Introducing Alkenes. 2003. Chemistry Guide. 24 Nov. 2008 <http://www.chemguide.co.uk/organicprops/alkenes/background.html>.

Clark, Jim. “An introduction to alkanes and cycloalkanes.” Introducing Alkanes and Cycloalkanes. 2003. Chemistry Guide. 24 Nov. 2008 <http://www.chemguide.co.uk/organicprops/alkanes/background.html>.

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  • University/College: University of Arkansas System

  • Type of paper: Thesis/Dissertation Chapter

  • Date: 17 November 2017

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