postlab 8

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organic 1 lab

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you can find attached post lab of experiment. I want someone to paraphrase it for me and minimize the similarity to 20% or lower. i want you to to paraphrase introduction, experimental procedures, results, discussion, and conclusion.

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Experiment 8 The SN2 Reaction: Factors affecting SN2 Reaction Done by: Mammar Al-Kalbani TA: Abiola Azeez 03/17/2017 Introduction: Chemical reactions are significant in producing everyday products. Every reaction has its factors and reasons to happen. An example of these reactions is substitution reaction in which a functional group or an atom is substituted by another (Meislich, 2001). In addition, there are two types of mechanisms involved in substitution reactions: SN1 and SN2. The SN1 mechanism occurs when “a tertiary alkyl halide reacts with a good nucleophile and weakly basic solvent, and the secondary alkyl halide reacts with a poor nucleophile and protic solvent.” On the other hand, when a primary alkyl halide reacts with a good nucleophile with a strong unhindered base or with a weak basic solvent it promotes SN2. Also, “when a secondary alkyl halide is being reacted with a poor nucleophile in a polar aprotic solvent” (Earley, 2009). There are factors controlling the rate at which the reaction happens (both speed and time). The main three factors that affect SN2 mechanism “are steric hindrance, the nucleophilicity (concentration and reactivity) of the reactant that substitutes the alkyl halide (nucleophile), and the nature of the leaving group (physical and chemical properties)” (Earley, 2009). Other minor factors can be the solvent that is used in a reaction (Weldegirma, 2017). In this experiment, an “SN2 reaction will be performed to examine how steric hindrance, nucleophilicity and nature of the leaving group affect the rate of an SN2 reaction” (Weldegirma, 2017). The figures below show the mechanism of SN2 reaction in trimethylamine and the possible side reaction of it. Reactions: Figure 1: SN2 reaction between trimethylamine and HC3I. Figure 2: Possible side-reaction from the first part Experimental Procedure: A mixture of the provided solvent was prepared in the ratio of 1:5:4 of Acetone: ether: pentane. In test tube #2, the same procedure was repeated as in #1. In test tube #3, 15 drops of 2bromopropane were poured in. RECORD observations. Melting point test was conducted to the collected product and compared to the list provided in the manual. 3 medium test tubes and 3 small ones were prepared. Another test tube with the unknown was prepared. Each set was labeled 1-3 (two sets total) 20 drops of trimethylamine were poured in test tube #1. Then 10 drops were added of methyl iodide. 20 drops of ethyldiisoprop ylamine and 10 drops of diethyl iodide were poured in test tube #3. Observe! 20 drops of triethylamine were added to the second set consisting of small test tubes. In test tubes #1 & #2 15 drops of iodoethane and another 15 drops of 1bromopropane were mixed. 40 drops of the unknown amine were poured in the seventh test tube plus 2 ml of the ‘1:5:4’ solvent. “10 drops of methyl iodide was added to the unknown test tube. The tube was shaken constantly.” Using vacuum filtration, the precipitate was collected and dried on a filter paper. Table of chemicals: Table 1 shows the chemical and physical properties of the chemicals used in this experiment Chemical used Chemical’s Structure Chemical Molecular M.P. and ’s weight B.P. (ºC) Formula (grams/mol e) 1-Bromopropane C3H7Br 123 Bp: 71 Mp: 70 Iodoethane C2H5I 155.97 Bp: 42.51 Mp: -111.11 2-Bromopropane C3H7Br 123 Bp: 59.37 Mp: -110.6 Triethylamine C6H15N 101.2 Bp: 89.5 Mp: -114.72 Tripropylamine C9H21N 143.267 Bp: 156 Mp: -94 Pentane C5H12 72.15 Bp: 36 Mp: -129.83 Ethyldiisopropylamine C8H19N 129.247 Bp: 127 Mp: -46 Acetone C3H6O 58.07 Bp: 56.03 Mp: -95 Diethyl ether C4H10O 74.12 Bp: 34.6 Mp: -116.31 Iodomethane CH3I 141.94 Bp: 42.43 Mp: 71.5-73 Results Tube Nucleophile n.o. Present Substrate used Solvent used Reaction Precipitati Color of on solution/ precipitate 1 Trimethylamine Iodomethane 1:5:4 of Yes Small to Yellow – (Acetone:Diethyl- (few no white ether:pentane) seconds) precipitati on 2 Tripropylaminne Iodomethane 1:5:4 of Yes (Acetone:Diethyl- (5 min) Yes Cloudy (white) ether:pentane) 3 Ethyl- Idomethane diisopropylamine 1:5:4 of _____ No Cloudy Yes Yes White (Acetone:Diethylether:pentane) 1 Trimethylamine Iodoethane _____ (60 sec) 2 Trimethylamine 1-bromopropane _____ _____ (cloudy) No Yellowish 3 Trimethylamine 2-bromopropane _____ _____ No clear 7 Unknown Methyl iodide 1:5:4 of Yes Yes cloudy (Acetone:Diethyl- rapidly ether:pentane) Melting Point of the unknown amine: 150-160˚C Unknown Salt: (C6H5)CH2N(CH3)3+ IDiscussion: In this experiment, both sets of test tubes used showed different results showing different factors affecting the substitution reaction (SN2). The first couple of test tubes showed rapid precipitations within short amount of time. This was because of the chemicals containing strong nucleophiles reacting with aprotic solvents and performed an SN2 reaction. On the other hand, there was neither reaction nor precipitation in test tube #3. “This was because of the steric hindrance on the substrate which caused the reaction SN2 to slow” (Earley, 2009). The alkyl halide is a strong leaving group as the first part of the experiment showed. Furthermore, in the second sets of small test tubes, test tubes #1 and #2 had fast results in which some coloring change and precipitations occurred. The reason behind this is that iodine is a better leaving group the bromine in SN2 reaction and the steric hindrance is “strong since it has a primary substrate, which is the best case for SN2 reaction to happen.” However, the third small test tube (reaction with 2-bromopropane) didn’t show any results and might needed more time to show any results. Moreover, for the unknown amine, the reaction happened immediately showing that the substrate is primary and the nucleophile was a strong one. In addition, the solvent (Acetone: Diethyl ether pentane) used in this experiment was aprotic and increased the rate of the SN2 reaction. The melting point test helped in identifying the product from the precipitate of the unknown amine and compare it to the quaternary ammonium salts list in the lab manual. The unknown was found to have a melting point about 150-160˚C that is near to (C6H5)CH2N(CH3)3+ I- that has a range of melting point of 178-179˚C. This concludes that the salt was (C6H5)CH2N(CH3)3+ I-. Although the melting point was little bit lower than the theoretical value, it was close enough to prove the identity of the unknown. Conclusion The experiment proved that SN2 reaction with the presence of strong nucleophile replacing a primary substrate and suitable solvent, the reaction would happen in a very fast rate. However, if the nucleophile is weak and is attacking a secondary leaving group, the reaction will not happen. The experiment was a success in accomplishing the objective, which is “performing SN2 reaction and evaluate the effect of the steric hindrance, nucleophilicity of the amine, and the nature of the leaving group on the reaction.” (Weldegrima, 2017). Such substitution reactions have many industrial uses. For instance, fluid isolations are done in fluids industries. PCB’s, for example, is “an insulating fluid that was used for a long time but it was banned later due to its affect to the environment” (Klein, 2013). References Earley, C. (2009). Reactions of Alkyl Halides: Substitution vs. Elimination. Web. Mar 12, 2017 Klein, D. (2013). Organic Chemistry, 2nd edition. Web. Mar 12, 2017 Meislich, H., Nechamkin, H., & Sharefkin, J. (2001). Schaum's Easy Outlines : Based on Schaum's Outline of Organic Chemistry by Herbert Meislich, Howard Nechamkin, and Jacob Sharefkin. New York: McGraw-Hill Professional. Web. Mar 13. 2017 Weldegirma, Solomon, Experimental Organic Chemistry Laboratory Manual, CHM 2210L. Department of Chemistry, University of South Florida Mason Ohio, 2017, pp. 46-48.
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