Organic Chemistry I
25 January 2013
The objectives of this lab are, as follows; to understand what occurs at the molecular level when a substance melts; to understand the primary purpose of melting point data; to demonstrate the technique for obtaining the melting point of an organic substance; and to explain the effect of impurities on the melting point of a substance. Through the experimentation of three substances, tetracosane, 1-tetradecanol and a mixture of the two, observations can be made in reference to melting point concerning polarity, molecular weight and purity of the substance. When comparing the two substances, it is evident that heavy molecule weight of tetracosane allowed it to withstand the increased heat as a solid for a longer duration. The melting point of the combined molecules was much lower than each in its pure form. The finding reinforces the idea of derivatives and their importance when identifying a substance based on melting point. The conclusions drawn from the data found in this lab will aid in the recognition of molecules based on the properties they illustrate.
The objectives of this lab are, as follows; to understand what occurs at the molecular level when a substance melts; to understand the primary purpose of melting point data; to demonstrate the technique for obtaining the melting point of an organic substance; and to explain the effect of impurities on the melting point of a substance. In this unit of study, I have learned that the physical properties of a molecule are commonly relied upon for identification. More specifically, a chemical’s melting point is often the physical property of choice for identification. The melting point of a substance is defined as the temperature at which the solid and liquid phases of a substance are in equilibrium with one another and both present at the same time. A molecule’s melting point is directly related to intermolecular forces within the substance; it describes its atoms attractive forces and how close the atoms are to one another within the compound. Using this knowledge obtained from the course work, I will experiment with two given organic compounds to enhance my understanding of melting points.
METHODS AND MATERIALS
Rubber bands (3)
Clean sheet of paper
Burner fuel stand
Thermometer- in- cardboard tube
Tetracosane Crystals- 0.2g
Tetradecanol Crystals- 0.2g
To begin this experiment, I must pour approximately 60mL of water into a glass beaker, allowing it to sit until room temperature is achieved. Next, I will pour the tetracosane crystals onto a clean sheet of paper crush them into a fine powder with the back of a spoon. A small amount of the powder will be collected and placed in the bottom of a glass capillary tube. My goal is to have the power occupy no more than 2mm of tube space; too much material will misguide a true melting point. Once inside the tube, I will secure the tube alongside a thermometer with a small rubber band; careful to place the bottom of the tube directly above the bulb of the thermometer. The finished structure is then placed into the water bath. It is critical at this point that water does not enter the glass tube.
Once the compound is secure in the beaker of water, the entire unit is placed onto the burner stand. Ignite the burner fuel and gradually increase the temperate while closely observing the compound for changes. Use caution in increasing the temperature gradually, as not to miss the correct boiling point and alter the data. A good standard to follow is increasing the bath temperature by no more than 5 degrees per minute. Note: a magnified glass is recommended to pay careful attention to the compound. Record the temperate when the first drops of liquid are noted, as the crystals begin to...
References: Fryhle, C. B., & Solomons, T.W.G. (2011). Organic Chemistry (10th Ed). Hoboken, NJ:
John Wiley & Sons Inc.
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