Answer Happy

Results:
Weight of crystals: 0.38 grams
QUESTION:
Deduce the limiting reagent and calculate the percent yield.
cyclopentadien MW 66 mole hp-41°C density-0.80 g/l. 21 maleic anhydride MW-mole mp-53°C diene ABCDEP Aa8bCcDdEe Normal No Spacing Experiment 5 Diels-Alder Cycloaddition Introduction As you are well aware, the general public regards chemical companies with skepticism at dienophile cs-Nethomene-56-endo-dicarboxylic anhydride MW 164g mp-165 best because of historically poor environmental track records. Advances in organic chemistry over the past 50 years have led to continuing improvements in the environmental friendliness of chemical processes, and the field of Green Chemistry has become a major new area of research. Green Chemistry attempts to minimize the environmental impact of chemical processes by following 12 principles that result in more benign processes. One of the principles is "atom economy" which states that "synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product." In other words, if most of what you add to the flask is incorporated into the product, then you will generate less waste. One example of an atom economical reaction is the Diels-Alder reaction, named for its discoverers Otto Diels and his student Kurt Alder. The Diels-Alder reaction is an example of a concerted [4+2] cycloaddition with a diene (4x electrons) reacting with a dienophile (2x electrons). No other reagents or catalysts are required to promote this reaction, making it very atom economical. The Diels-Alder reaction is one of the best ways to make six membered rings and due to its high efficiency and stereospecificity this reaction is considered to be one of the most important and powerful reactions in organic chemistry. Because of this, Diels and Alder were awarded the Nobel Prize in 1950. The general scheme for a Diels-Alder reaction is shown below: diene new bond being made transition state -101-0 product diophile AaBbCcDc AaBbCcDdE Aa Heading 1 Heading 2 new bond A vew of the important arbital interactions that occur in the transiti MacBook Air new bood Focus
Mailings Review M Lab 5 View EndNote X9 Tell me ¶ 32 Possible orientation 1: Endo E A concerted reaction is one that has a single transition state with no intermediates. Thus, any stereochemical information that is present in the diene and dienophile starting materials is translated into the product without scrambling. Note that no bonds are broken during a Diels- Alder reaction, and thus if a ring is present within either the diene or dienophile, that ring will also be present in the product. Possible orientation 2: Exo AaRbCcOdEe Normal In the Diels-Alder reaction between cyclopentadiene and maleic anhydride, the diene (cyclopentadiene) can approach the dienophile (maleic anhydride) in the two possible ways (orientations) shown below. Experimentation has revealed that the endo transition state is more favorable. This is counter intuitive because at first glance there would appear to be more steric interactions in the endo transition state. However, it has been rationalized that there is a stabilizing interaction between the orbitals of the diene and the orbitals of the carbonyl groups on the maleic anhydride (they stack on top of each other). This stabilizing interaction cannot occur in the exo transition state, which makes the endo transition state more favorable. In fact, in this case the difference in energy between the endo and exo transition states is so large, only the endo product is formed. 4 Possible ways the diene and dienophile can approach each other: - {- Heat new cond ANBOC DEP No Spacing new bond new bond H Note that hydrogens are on same face as CH₂ bridge |AaBbCcDd AaBb CCDdE Heading 1 Heading 2 Note that hydrogens are on opposite face as CH₂ bridge Two molecules of cyclopentadiene will react with each other (dimerize) via a Diels-Alder reaction within hours. In fact, you can't buy monomeric cyclopentadiene because a few hours after putting it in a bottle you would have only the dimer. Where then, you ask, will my cyclopentadiene come from? Like most reactions, Diels-Alder reactions are reversible. When the cyclopentadiene dimer is heated, a retro-Diels-Alder reaction occurs to liberate two equivalents of cyclopentadiene, which can be collected by distillation and used within a short period of time; monomeric cyclopentadiene must be prepared fresh for each lab period and your ever faithful TA will prepare it for you before the lab begins. Objective Cyclopentadiene and maleic anhydride will react by a Diels-Alder cycloaddition via the will be onstalline and will he
Mailings Review View EndNote X9 Tell me V == = 1- ¶ | AaBbCcDdEe Normal AaBbCcDdEr No Spacing AaBbCcDd AaBbecE Heading 1 Heading Objective Cyclopentadiene and maleic anhydride will react by a Diels-Alder cycloaddition via the endo orientation to provide a norbornene product. The product will be crystalline and will be isolated by filtration. The yield and melting point of the product will be determined. Experimental Procedure 1. Add 0.4 g of maleic anhydride to a test tube. 2. Add 1.0 mL of ethyl acetate to the maleic anhydride and dissolve by stirring with a spatula (add an extra 0.5 mL ethyl acetate if warming does not dissolve the maleic anhydride). 3. Once the maleic anhydride is dissolved add 2 mL of hexane. 4. In the hood, add 0.4 mL (20 drops from a Pasteur pipette) of cyclopentadiene to the dissolved malcic anhydride and mix with the spatula. Be sure to do this in the hood as cyclopentadiene is fairly stinky. 5. Return to your lab bench and allow the tes tube to sit at room temperature for 5 minutes. 6. Immerse the test tube in an ice-water bath for 2 minutes to complete crystallization. 7. Use a pipette to breakup the crystals. 8. Collect the crystals by suction filtration using a pre-weighed filtration apparatus (suction filter and filter paper). Rinse out any crystals remaining in the test tube with 3 mL of hexanes. 9. Allow air to draw over the crystals for 2 minutes to dry them. Scrape the crystals off of the filter paper from the Buchner funnel onto a larger piece of filter paper, the 11 cm papers work well. Fold the paper in half with the crystals inside (like a taco). Rub the sides back and forth to dry the crystals. 10. Note the yield of crystals by reweighing the funnel and its contents. 11. Take a melting point of the crystals.