Lesson 7 Lab: Synthesis of Nylon and Recrystallization
PART 1
Begin by viewing the following Thinkwell video
13.3.2 CIA Demonstration: The Synthesis of Nylon
After you watch the above video, answer the questions below in sufficient detail:
(a) (2 pts.) What is the name of the type of reaction that you see in this demonstration? Describe IN YOUR OWN WORDS what happens, generally speaking, in this type of reaction. Be detailed in your discussion.
Answer: According to Thinkwell (2001), the name of the type of reaction that I see in this demonstration is condensation polymerization which is basically substance separating two or more of the polymer molecules when combined. “Reaction occurs only at the interface between the two solutions where the two molecules come in contact.
(b) (2 pts.) There are two chemicals used in this reaction, 1,6-hexadiamine (which is in a water solution) and adipoyl chloride (which is in a hexane solution). Think back to what you learned in this course about solutions and intermolecular forces. Why don’t these to “mix” together (in other words, make a homogenous solution) when combined? Why do they separate into layers? Be clear and detailed in your response.
Answer: According to Thinkwell (2001), Adipoyl chloride cannot donate any H-bonds, and can only accept two. Because of the differences in polarity, and primarily 1,6- hexanediamine’s ability to hydrogen bond with itself, they will not mix. Hence, the Adipoyl chloride solution floats on the surface of the 1,6-hexanediamine solution.
(c) (2 pts.) What functional groups are the key players in this reaction? How so? Explain clearly and in detail.
Answer: According to Thinkwell (2001), the key players in this reaction is an aqueous solution of 1,6-hexanediamine and a solution of adipoyl chloride in hexane are layered in a beaker. Hexane is nonpolar and less dense than water and will form a layer on top of the water. The reaction occurs only at the interface of the two solutions where the two monomers are able to come into contact with each other. A condensation polymerization takes place at the interface between the 1,6 hexanediamine and the adipoyl chloride resulting in nylon 6,6 and HCl.
The amine groups on both ends of 1,6- hexanediamine react with the acid chloride groups on either end of the adipoyl chloride molecule toform a polymer.
(d) (2 pts.) Explain, in as much detail as possible, why the nylon is only created at the INTERFACE between these two solutions.
Answer: According to Thinkwell (2001), the two solutions are not miscible so the reaction can only occur at the interface, and that is why nylon is only created at interface. When these two solutions are in contact with each other, the monomers can only react at the interface between them. The nylon rope is drawn from this polymer film that forms at the interface. As soon as old polymer film is removed, new film forms immediately behind it. Thus, the reaction results in the continuous creation of polymeric material until at least one of the reactant monomers is completely consumed. The nylon rope that formed in the solution at the interface between the two solutions is called a polymer chain.
PART 2
Please watch the following Thinkwell video:
15.1.2 CIA Demonstration: Recrystallization
After you watch the above video, answer the questions below in sufficient detail:
(a) (3 pts.) Describe, in as much detail as possible, the process of recrystallization as a method for purification of a solid. How does it work? What do you do?
Answer: According to Thinkwell (2001), the process of recrystallization starts with impure solids. Therefore, in order to make them pure, you want to break them apart by using a type of solution that can break the bonds in between the crystals. So the process of recrystallization is: Step 1: Dissolve the solids by using appropriate solvents, apply heat if necessary. Step 2: by dissolving the impure substances, you are allowing the impurity to break apart to pure substances. Now similar substances will attract each other much more likely that for impure substances to attract each other. Step 3; Place the solvent/solute into a cold fridge and allow for the solutes to crash into solution. Thus, the crystals that come from it are typically pure.
(b) (2 pts.) How do you make a “supersaturated” solution—what are the specific steps? How is this different than a “saturated” solution?
Answer: According to Thinkwell (2001), supersaturated solution refers to a solution that contains more of the dissolved material than could be dissolved by the solvent under the solubility amount. In order to make it you have to continue to add the dissolving material, even after it stops being dissolved. It's different than a saturated solution because it contains more dissolved material than the solvent can dissolve.
(c) Describe SPECIFICALLY what happens when solute is added to:
(1 pts.) a saturated solution
Answer: According to Thinkwell (2001), when solute is added to a saturated solution, it will not dissolve which will cause the solute to settle out making a separate layer.
[ii] (1 pts.) an unsaturated solution
Answer: According to Thinkwell (2001), when solute is added to an unsaturated solution will be able to dissolve more because it contains a less amount of solute than is required to saturate it.
[iii] (1 pts.) a supersaturated solution
Answer: According to Thinkwell (2001), when solute is added to a supersaturated solution will make it impossible to dissolve because that is more concentrated than a saturated solution.
(d) (2 pts.) What is the role of vacuum filtration in this process of Recrystallization? How do you do it? Be detailed and specific, and include all steps.
Answer: According to Thinkwell (2001), the role of vacuum filtration in this process of Recrystallization is to further purify the sample once the sample has crystallized. First you turn on the vacuum, wet the filter paper, and collect crystals in to the filter. Following that you wash the crystal with water, cold water, to clean its colors off making it near colorless.
(e) (2 pts.) Suppose we are dealing with calcium chloride as opposed to the chemical in the video. If a solution contains 70 g of calcium chloride per 100 g of water at 25 degrees Celsius, is the solution unsaturated, saturated, or supersaturated? Explain your answer. You may want to refer to Figure 13.4 in your text for help, or perhaps refer to the image at http://chemistrysolutions.files.wordpress.com/2011/03/capturada16.jpg..
Answer: Looking up the literature for CaCl2, it is saturated at 74.5 g/100mL (20 °C). In the problem, the temperature is increased, and in general, as temperature increases, so does the solubility curve. Since in the problem 25 C is the temperature, the saturation point of 74.5 is going to be passed, thus the solution is supersaturated at 25 degrees C at the 70/100 g concentration. However, looking at a solubility curve, you can easily see that the curve for CaCl2 is above that of NaCl (which is the reference solute dissolved in 100 mg of H20). Anything above this line is supersaturated and below unsaturated. Therefore, since we have 70/100 gm water the solution is unsaturated.
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