Examining The Bromination And Debromination Of Cholesterol Biology Essay

Examining The Bromination And Debromination Of Cholesterol Biology Essay Bromination/debromination which is an important organic reaction that aims in purification of crude cholesterol from impurities which include 3-cholestanol, 7-cholesten-3-ol, and 5,7-chlestadien-3-ol was performed in a laboratory scale for two weeks. Due to steric constraints, only cholesterol reacted with bromine and crystallized from the solution making it possible to be separated (Feiser, and Williamson 63). The dibromocholesterol formed is regenerated by reacting with Zinc dust. In addition, three methods were used to evaluate the effectiveness. These were Sodium Iodide test, Silver Nitrate test, and Sulfuric acid test. NaI test showed a positive response as color changed to yellow. The formation of the precipitate also indicated a positive result. The sodium iodide reagent reacted with 1 ° and 2 ° alkyl halides through an SN2 mechanism.  On the other hand, the silver nitrate reagent reacted with 2o and 3 ° alkyl halides through an SN1 mechanism.   Negative results were observed for both the commercial cholesterol and 1-chlorobutane (Zubrick 38). Conversely, the t-butyl chloride gave a positive result for the AgNO3  test and a negative result for the NaI test. The synthesized cholesterol was 0.29 gram and the theoretical yield was 1.08 gram. This gave a percent yield of 26.9 gram. Although this was a low yield the TLC analysis confirmed a high purity of the synthesized cholesterol. The melting point of the synthesized cholesterol and commercial cholesterol seems to fall in the same range. This confirms the purity of the synthesized cholesterol. TLC analysis was carried out to confirm the purity of the analysis. The distance traveled by commercial cholesterol was 5.5 whereas that travelled by the synthesized cholesterol was 4.6. The absence of other spots on the TLC plate confirms that there were no contaminations present in the sample. Introduction Cholesterol is an important steroidal compound found in both animals and plants. Despite the fact that cholesterol causes diseases, it plays a vital role in life. For example, cholesterol is the main structural component in cell walls and in myelin sheath formation. It is also a major precursor for most steroid hormones. Crude cholesterol is isolated from natural sources and various methods have been used in its purification. Crude cholesterol contains approximately 3-5% contamination. Some of the contaminants are 3-cholestanol, 7-cholesten-3-ol, and 5,7-chlestadien-3-ol shown below. Figure 2: Some common contaminants of commercial cholesterol The main objective of this experiment was to purify commercial cholesterol using organic reaction chemistry, including the use of the electrophilic addition. For complete purification of cholesterol from the above impurities is achieved by a reaction of bromine with cholesterol to generate dibromocholesterol. Because of the steroid ring structure present in these compounds that causes steric constraints, only cholesterol reacts with bromine to form an insoluble diaxial dibromo compound through electrophilic addition. On the other hand, cholestanal does not react with bromine and the other two contaminants are dehydrogenated by bromine leading to formation of soluble dienes and trienes respectively. The dibromo-cholesterol precipitates as a solid leaving the other impurities in the reaction solvent. A purification step such as solvent washing or crystallization is carried out to separate the solid from the impurities. The so lid dibromo-cholesterol is then reacted with zinc in order to regenerate pure cholesterol. Figure 1: Reaction Scheme for the Bromination/Debromination of Cholesterol To test the effectiveness of this reaction three different chemical tests namely sodium iodide in acetone, silver nitrate in ethanol test, and sulfuric acid test, were performed. Each of these tests is selective for a specific functional group. Dibromocholesterol contains both primary and secondary alkyl halides and reacts with a sodium iodide in acetone and silver nitrate in ethanol to form a precipitate or a cloudy solution. In addition, the presence of double bonds in dibromocholesterol in form of alkene makes it possible for the formation of a fluorescent green sulfuric acid layer and a red chloroform layer when reacted with sulfuric acid (Landgrebe 78). Material and Methods 1g of commercial cholesterol was added to a 25 mL Erlenmeyer flask. 7 mL t-butylmethyl ether was measured with a graduated cylinder and added to the flask containing the cholesterol and a magnetic stir bar. A water bath was then set up on the hotplate in the hood. The Erlenmeyer flask contain the reaction solution was inserted into the water bath and clamped as shown below. The heat and the stirrer were turned on and gently heat until all the cholesterol dissolved in t-butylmethyl ether. Figure 3:   Set-up for bromination reaction (Note: the actual reaction mixture is not blue) The flask was removed from the water bath after all the cholesterol was completely dissolved and allowed to cool to room temperature. After the cholesterol solution was cooled, the flask was clamped to the ring on the hot plate as shown in figure 4 and stirred without heating. A burette was then used to dispense 5 mL of bromine solution into the flask. A precipitate solution formed almost immediately. Figure 4:   Set-up for the Addition of Bromine The water bath was replaced with ice and tap water and the reaction solution stirred intermittently with a glass stir rod for ~ 10 minutes to complete the crystallization of the product. About 20 mL of the t-butylmethyl ether acetic acid solution was then dispensed in a clean 50 mL Erlenmeyer flask which was clamped to a ring stand and allowed to cool in the ice bath. A vacuum filtration was done using a Buchner funnel and filter paper. The solid in the filter was washed using ~10 mL of the cooled solution of t-butylmethyl ether acetic acid and then with ~10 ml of methanol. The solid was then allowed to dry with the vacuum on for about 5 minutes. the dibromocholesterol melting point was measured and recorded. The dry solid was weighted and sealed in a vial and stored for next experiment. To debrominate cholesterol, 20 mL of t-butylmethyl ether, 5 mL of acetic acid and 0.2 g of Zn dust were added into the Erlenmeyer flask containing the dibromocholesterol solid. The mixture was swir led for 5-10 minutes in the hood and sonicated in 5 minutes to allow the reaction to go completion. After sonication the solids present were removed by gravity filtration method into a clean 125 mL Erlenmeyer flask. The filtrate was transferred to a 125 mL separatoryHYPERLINK http://community.acphs.edu/bbcswebdav/institution/Arts%20and%20Sci/Courses/CHE211/Common/lab/Organic-sde/BP-Dist/BP_General.html funnel in which 20 mL of deionized water was added, shaken and allowed to separate into layers. The two layers formed were then separated as water layers and organic (ether) layers. The ether layer was washed with 20 mL of 10% NaOH and then 20 mL of saturated NaCl solution. 100mg of the drying agent magnesium sulfate was added to the organic layer and the solution swirled until dry. The drying agent was removed by gravity filtration using a glass funnel fluted filter paper and a very dry 50 mL Erlenmeyer flask. The flask was placed in a warm water bath and then ice cooled for 10 minut es until all but 5 mL of the ether remained following a precipitate formation from the solution. The remaining solvent was decanted and the synthesized cholesterol transferred and allowed to dry in the hood for 20 minutes.The dry solid was weighed and the weight recorded. In addition the melting point was also taken and recorded. To evaluate the effectiveness of the bromination reaction three chemical reactions mentioned above were carried out. NaI in acetone test Five test tubes labeled A, B, C, D and E were used for this test.   About 30 mg of the commercial cholesterol starting material was added to tube A; ~30 mg of dibromocholesterol to tube B; ~30 mg of the synthesized cholesterol product to tube C; ~0.3 mL of 1-chlorobutane to tube D; and ~ 0.3 mL of t-butyl chloride to tube E.   In addition, about 3 mL of acetone was added to each tube to completely dissolve all the compounds.   Solutions A-E was used to do the NaI in acetone test as well as the AgNO3 in ethanol test. Tubes A-C did the TLC as well. The NaI in Acetone and AgNO3 in Ethanol tests were performed by setting up a test tube rack containing ten small test tubes. The test tubes were labeled N1 N5 and A1 A5. 1 mL of NaI in acetone reagent was added to test tubes N1 N5, and 1 mL of AgNO3 in ethanol reagent to test tubes A1 A5. This was followed by adding 5-8 drops of A solution to test tube N1 and tube A1, 5-8 drops of solution B to test tube N2 and tube A2, 5-8 drops of solution C to to test tube N3 and tube A3, 5-8 drops of solution C to test tube N4 and tube A4, and 5-8 drops of solution C to test tube N5 and tube A5. The test tubes were heated for a while and all the observations recorded. The sulfuric acid for alkenes test was performed by additional solutions of cholesterol and dibromocholesterol with five dry-cleaned test tubes 1-5. 10 mg of commercial cholesterol was placed in tube 1, ~10mg of the dibromocholesterol to tube 2 ~10 mg of your synthesized cholesterol to tube 3, ~10 mg of 2-chlorobutane to tube 4, and 10 mg of cyclohexene to tube 5.  About 1 mL of chloroform (CHCl3) was added to each tube and vortex to completely dissolve all solids.   In addition, 0.5 mL of H2SO4 was then added to each tube. The observation for this reaction was recorded in the notebook. The TLC analysis of cholesterol and dibromocholesterol was performed by obtaining a silica gel TLC plate and setting it up to run TLC analysis on solutions A-C above. The plate was spotted with each solution and developed by placing the plate using 30% ethyl acetate: 70% hexane as the mobile phase. The developed plates were viewed under UV lamp and in the I2 chamber and observations recorded. Results Table 1 Percent Yield of synthesized cholesterol Actual Yield 0.29g Theoretical Yield 1.08g Percent Yield 26.9% Mass of Synthesized Dibromocholesterol was 1.57g Table 2 Melting Point Test Compound Temperature  °C Commercial Cholesterol 144.6-150.3 Dibromochesterol 105-109 Synthesized Cholesterol 147 Table 3 Sodium Iodide test Compound Time Vortex Temp First Sign of Reaction Com. Cholesterol None Dibromocholesterol + Yellow Synthesized Cholesterol + Chunky Yellow 1-Chlorobutane + Yellow Tert-Butyl Chloride + Cloudy Table 4 Silver Nitrate test Compound Time Vortex Temp First Sign of Reaction Com. Cholesterol None Dibromocholesterol + Cloudy Synthesized Cholesterol + Cloudy Yellow 1-Chlorobutane None Tert-Butyl Chloride + Cloudy Table 5: Sulfuric Acid Test Compound Time Vortex Temp First Sign of Reaction Com. Cholesterol + Color Dibromocholesterol + Color Synthesized Cholesterol + Color 1-Bromobutane None Tert-Butyl Chloride + Color Table 6: Thin Layer Chromatography: In 30% Ethyl Acetate/70% Hexane Commercial Cholesterol 5.5 1.0 5.5 Dibromocholesterol 4 0.73 5.5 Synthesized Cholesterol 4.6 0.84 5.5 Discussion The yield of the synthesized cholesterol was .29 grams (Table 1). The theoretical yield was 1.08 grams. The actual yield was calculated by taking the difference of the weight of the round bottom flask and the synthesized cholesterol by the synthesized cholesterols weight alone. The percent yield was calculated to be 26.9 percent. The synthesize process was not efficient due to the low yield and percent yield of the synthesized cholesterol. The melting point of the synthesized cholesterol and commercial cholesterol seems to fall in the same range. This confirms the purity of the synthesized cholesterol. NaI test showed a positive response as color changed to yellow. The formation of the precipitate also indicated a positive result. The sodium iodide reagent reacted with 1 ° and 2 ° alkyl halides through an SN2 mechanism.  On the other hand, the silver nitrate reagent reacted with 2o and 3 ° alkyl halides through an SN1 mechanism.   Negative results were observed for both the commercial cholesterol and 1-chlorobutane. Conversely, the t-butyl chloride gave a positive result for the AgNO3  test and a negative result for the NaI test. The stationary phase of the TLC test was the silica gel TLC plate and the mobile phase was 30% Ethyl Acetate/70% Hexane (Table 6). The distance traveled by commercial cholesterol was 5.5, and for the synthesized cholesterol was 4.6. The difference in the distance traveled and the R f values of the samples commercial and synthesized cholesterol were pure. Since there were no other spots visible on the TLC plate was a clear indication that there were no contaminations of other chemical compounds present in the sample.

Epic Hero

Epic Hero Essay Heroes are strong, brave, loyal, and intelligent people that help us when we run into trouble and inspire us. Odysseus displays these characteristics, in the epic poem â€Å"The Odyssey. † He's on a quest to get back home and to regain his throne, but a series of unfortunate events occur that makes his journey long and treacherous. In his various adventures like The Cyclops, The Land Of The Dead, and The Lotus-Eaters, Odysseus shows examples of his heroic characteristics. In Odysseus's adventures, he comes across a cyclops named Polyphemus. When Odysseus was trapped in Polyphemus's cave, he told him his name was â€Å"nhbdy. † He also knew that he shouldn't have killed him in his sleep because he and his men wouldn't have been able to escape. Through that experience, he proved that he was an intelligent and cunning person. When Odysseus went to the Land of the Lotus-Eaters, he and his men rested there and relaxed. His men were pressured to eat the lotus plants and it made his crew all looney and â€Å"high. Odysseus showed his intelligence and loyalty by not eating the lotuses and carrying his men back to the ship. With every action Odysseus takes, it exposes him even more as an epic hero. On his journey to The Land Of The Dead, Odysseus displays extraordinary actions that truly show he is an epic hero. He was brave enough to even go down to the underworld and strong enough to undergo the heat. He fended off evil spirits and met his friend and his mother. Odysseus, raider of cities used his strength to go through those events. Heroes are strong, smart, devoted, and courageous people that help and influence us. Odysseus, king of Ithaca, from the epic poem â€Å"The Odyssey,† shows that he surely is an epic hero. He went through a whole bunch of horrible events that has proven his existence as a great role model. It is people like Odysseus that makes this world a better place and he influences people to become more a hero everyday.

Western Civilization Essay Narrow Topics Ideas

Western Civilization Essay Narrow Topics Ideas Your term paper is forecast to be rather lengthy. What remains is an issue of filling in the blank spots to finish the very first draft. Do not neglect to incorporate a rebuttal paragraph. Just don't attempt to encompass the entirety of this kind of huge issue in 1 paper. The Hidden Secret of Western Civilization Essay Narrow Topics Each and every culture has a typical heritage that is critical in the evolution of a specific culture. This European culture may be equated with western civilization and way of life. Western civilization has brought a good deal of changes in the lifestyle of a lot of people. It is a broad term since there are so many aspects to learn about. As stated by the Merriam-Webster Dictionary a civilization is a fairly high degree of cultural and technological improvement. Today, the majority of the individuals concentrate on such western languages hence forgetting their very own native language. There are a few foods which either African culture or religions don't allow people to consume. For knowledge is power and the quantity and caliber of knowledge or information has fueled the development of civilizations since the outset of history. In high school and middle school, you aren't necessarily anticipated to compose large, serious argument essays. With these kinds of points, therefore, you receive a notion of what things to include and the way to compose your essay. When you have question please allow me to know. Simple but intriguing topics will do, and you need to just demonstrate you know what an argument essay is and the way to develop and format one. The western civilization essay is an extremely wide subject. Freud states that almost all of the society is affected by this. It's the refinement of ideas and manners in society. To begin with, I do agree with Gaddis in that historical consciousness is among the important elements which should be developed by means of a society. If you quit attending class, however, it's your responsibility to guarantee you are officially withdrawn from the training course. With My Homework Writers, you always have the option to locate any type of assistance you demand. Writing research papers can lead to a lot of anxiety. Select a time period or locality to concentrate on. The Western planet, also called the West and the Occident, is a term referring to unique nations based on the context. Western civilization is wholly different in many of means. It took a long time. Generally, it is not all about connection with the European nation but with every country which accepts its ideas. The True Meaning of Western Civilization Essay Narrow Topics The opinion depends upon insufficient knowledge on the topic or distinct forms of intellectual sadism that westerners were displaying. Constitutionalism was the manner of the future and in my personal opinion it was the ideal approach to go. Furthermore, a narrow approach provides another benefit. Make sure you get a strong conviction for a single side or the other for any topic that you select to write about. That way your topic isn't going to be too wide. This topic is significantly more focused than mummies! You should make sure you select a topic that is more specific. You need to make sure you select an interesting and appropriate topic. When you are managing this sort of essay, you can decide to write it on a topic that's controversial because then there's a great deal of information to support either side that you would like to pick. Generally, western civilization is a comparatively wide topic to cope with. If you wish to turn to important topics which impact the whole of society, social issues are really an inexhaustible field. Alas, many students give little idea to their topic. Western Civilization Essay Narrow Topics Help! You will be able to collect the facts you need in no moment. Besides necessity to put money into the health care field, people also open up the concept that things can occur, and people ought to be ready. It truly just must be something which you want to know more about and something that you may think of a strong issue to discuss. As we use a lot of unique substances in our everyday lives it's clearly likely to be of value to know something about them so that we're able to use them more effectively. The Number One Question You Must Ask for Western Civilization Essay Narrow Topics You should begin to develop an outline as soon as you start doing some research. Selecting a suitable research topic is imperative to producing a top quality research paper. As you do your research, you're going to be in a position to judge whether you're on the correct track or not. To accomplish a balance, the research should incorporate a combination of primary and secondary sources.

Leons Holocaust - Free Essay Example

Sample details Pages: 4 Words: 1196 Downloads: 2 Date added: 2019/04/26 Category History Essay Level High school Tags: Holocaust Essay Did you like this example? Leons father has been saving up for a long time for his family to move in with him. When he earned enough money from his well paying job, the family bought a super tiny apartment and moved in with their two parents, one sister, and 4 boy family. With an already scarce amount of food and water, the family had to do everything they could to find money, food, and even a job. Don’t waste time! Our writers will create an original "Leons Holocaust" essay for you Create order The InvasionThen it happened, the Germans came and took over everything. Before, Leon made friends with other boys that werent even Jewish like him. But, after the Germans came, they abandoned Leon only because he was Jewish. The Jews that were about 10 years and older, had to wear a sleeve with the sign of David on it. But, Leon never wore that sleeve, and it could have cost his life. Now and then, I would sit on a park bench just to prove I could do what I wanted, resisting the Nazis in my own small way, Leon saidIt was a hard time for Leon and his family because they had to make the decision for Leons older brother to go back to their old village, with his girlfriend. Leon was devastated. His brother was his best friend, yet he would most likely never see him again. After a little while of the Germans take over, the Jews had to move out and move into an enclosed community and were forced to do hard labor. But, the only people that didnt have to go, were the special few on Schindlers list. Schindlers list basically includes a few lucky people that Schindler (a German man himself but who believes in Jews rights) choose to save from death because they were good enough to keep alive only to do work.So, because Leons father was a very skilled glass worker, their family got spared to be on Schindlers list. Leon thought he was safe, his parents thought they were safe. But, that wasnt the case. You can NEVER be safe when your being taken over by the Germans (and especially when they can do whatever they want to you). But, then the Germans barged in and took Leons older brother, for no reason at all. They took him away, and Leon knew that would be the last time he saw his best friend. His brother. Hiding After that, Leon and his family knew they had to hide. So, while all the Jews were moving out, Leon, his mother, and their next-door neighbor and son devised a plan. To hide. So they found a cellar to hide in for two or three days straight. Without food or even water. After the hiding though, Leon knew they wouldnt get by that easily. Only about 1,098 Jews were on Schindlers list in the camp. When it was time for them to leave for work, the family moved into an even smaller apartment shared with even more people. Schindlers list Work to DIE forOnce they started working for Schindler, it wasnt all fun and games. It was very hard work and everyone only get one meal a day, disgusting soup. And often enough, Leon had to sneak out and find food in the trash cans, and around the ground. But, since the kitchen workers were Jews as well and while Leon got to know them, when it came to lunch time, Leon always got a little extra food. During work though, Leon and along with everyone else never knew what would happen. Sometimes, a German man named Amon Goeth (who is the boss of Schindler and has complete control of the business) came in and kept a close eyes on the Jews. But the worst part was that he could do anything he wanted, even if that meant killing the Jews, just for fun and game. And nobody dared to stop him. Once, Amon came when Leon was doing work with the snow, he came and made his men take all if the Jews and hit them with leather whips. As the whips came, the Jews were made to call out the number of whips , and if they didnt the whips started over again from one to 25. Although I was numb from the cold, the pain seared through me each time, like being branded by a poker. Leon said putting in his opinion. Whenever he went to Leons working space, Leon got all stiff and scared, especially because he saw Goeth come in one day and take a couple of Jews out with a gun, and those two Jews had no idea he was there. He seemed to thrive on inflicting agony on on the helpless. Leon wrote. But, there was one sort of encouraging thing, whenever Schindler came in, he went up to Leon and talked with him. (considering Leon was one of the youngest Jews on his list) While Leon stood on his little wooden box to give him a boost, they talked for a while. Yet, with all the hard labor work, it didnt make it the tiniest bit easier for Leon.At night, Leon and his family were separated and couldnt sleep in the same place. So, a couple times Leon snuck out to try and find his father and brother first. It took him awhile, but Leon was finally able to find them. But, Leon had to be really stealthy, because if Goeth ever found out or saw it, he wouldve killed Leon right away and not regret anything. He also tried to find his mother, with the same circumstances. I was so small and thin, and my hair was so shaggy, I could pass for a girl; I knew I would be severely punished if I were discovered. Leon wrote when he tried sneaking into the womens bunker to try and find his mom. While the war was coming to an end, Leon always keep the thought in his head that he was going to be killed by the very last bullet in the war. And that thought stuck in his mind throughout the whole holocaust. But that wasnt the case because Leon survived to tell the story.Leon changed his name from Leib Lezjon to Leon when he came to America, but on Schindlers list, he was known as Leib Lezjon, with the rest of the Lezjons. Free at last!When the war finally ended, Leon, his mom, dad, brother and sister then traveled to America for a brighter future. Leon was still young then so he still went to school. Leon then graduated with a teachers license and taught high school kids. Eventually Leon got married, had kids, became an uncle, and soon a grandfather.When Leons family first made it to America, Leon tried to tell his experiences during the holocaust, but nobody would ever listen. So he keep his experi ence to himself. But, after a slight interview with the newspaper, everyone soon knew Leons story and wanted him to show up to events for speeches, and people even wanted autographs. And one fun fact was that whenever Leon gave his speeches, he never read off a script, it was all improvised.