Fordham University Investigating the Regioselectivity Of 1 Hexene Hydration

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Organic chemistry 1 lab homework assignment based on the concept of Investigating the Regioselectivity of 1-hexene hydration. I need someone who is in expert in organic chemistry! I also attached lectures notes and procedure of the experiment to guide the tutor through the problems, so they can better understand how to solve the questions.

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Investigating the Regioselectivity of Unsymmetrical Alkene Hydration: Hydration of 1-Hexene A fundamental and industrially important reaction of alkenes is the addition of the Scheme 1. Commercial synthesis of ethanol elements of water to the alkene C=C in the presence of an acid catalyst to afford an alcohol; e.g., most of the ethanol produced for industry is not made by alcoholic fermentation, but by an addition reaction between ethylene and water (Scheme 1). Ethylene is a symmetrical alkene, and only a single isomer of Scheme 2. Two-step hydration of an unsymmetrical alkene an alcohol could result upon hydration; however, hydration of unsymmetrical alkenes (regardless of their configuration; E/Z) could afford two possible alcohol isomers (Scheme 2). In this experiment you will use an older industrial process to hydrate l-hexene (a terminal, and thus unsymmetrical alkene) by treating it first with 85% (w/w) H2SO4 followed by heating the intermediate product (a sulfuric acid ester) in the presence of water, thereby hydrolyzing the ester group to liberate an alcohol (Scheme 2). You will then purify the alcohol product by simple distillation and determine which alcohol isomer was formed by boiling point determination in comparison with the reported boiling points for the possible isomeric alcohol products. Before coming to lab remember to consult the MSDS for all chemical substances. CAUTION: All concentrated (>50%) aqueous solutions of sulfuric acid, which includes 85% (w/w) sulfuric acid, are highly corrosive; avoid skin/eye contact by wearing gloves, eye protection and a buttoned up lab coat. Avoid direct contact with all other reagents/reactants/products in this experiment and work in a fume hood as much as possible. NO FLAMES will be allowed in the lab as ether and 1-hexene are highly flammable. Fig. 1 reaction flask Steps in procedure Fig. 2 reflux apparatus 1) In a clean and dry 50-mL Erlenmeyer flask place 10 mL of 85% (w/w) H2SO4 followed by 5 mL of 1-hexene. 2) Gently slide a 1-inch magnetic stirring bar into the flask, place the flask on top (and in the center) of a magnetic stirrer, loosely cork the flask, and securely clamp it to a stand. Vigorously stir the mixture using a magnetic stirrer for 15 minutes (Fig. 1). Note: 1-hexene and 85% H2SO4 are nearly immiscible and the mixture must be stirred rapidly for the reaction to take place! The reaction is mildly exothermic and the mixture gradually becomes homogeneous (i.e., one layer). - 3) Add another 5 mL of 1-hexene, loosely cork the flask, and rapidly stir the mixture for 15 minutes. 4) Securely clamp a 100-mL round-bottomed (RB) flask to a ring stand and place 20 mL of tap water in it. Then, using a liquid funnel, add the contents of the 50-mL Erlenmeyer flask to the RB flask containing the tap water. 5) Place 10 mL of tap water in the 50-mL Erlenmeyer flask, swirl the flask and add the rinse to the RB flask. 6) Gently swirl the RB flask, attach a condenser to the RB flask and drop a boiling stick (instead of a stone) into the flask directly through the opening at the top of the condenser (see Fig. 2). The mixture in the RB flask should consist of two layers after you add the contents of the Erlenmeyer flask. 7) Connect thin-walled tubing to the water inlet (lower nozzle) and water outlet (upper nozzle) of the condenser (see Fig. 2), and place the end of the outlet hose into the sink. Carefully open the faucet to afford a gentle stream of water, and then connect the inlet hose to the faucet. 8) Using a heating mantle attached to a voltage regulator, heat the contents of the RB flask to reflux for 5 min. Note: Set the voltage regulator to about 3.5 and start timing the reflux only after the liquid in the flask has come to a boil and you observe some condensate dripping back into the flask! 9) Lower and completely remove the heating mantle, and allow the flask to cool for a minute or so in air. Then cool the flask in an ice-water bath for a further 5 min (you can use the porcelain bowl in your lab drawer for the ice-water bath). The condenser must remain attached to the flask and water must be flowing through the condenser during ice-cooling. 10) Mount a separatory funnel on an iron ring attached to a ring stand. Then, remove the condenser and, using a liquid funnel, pour the contents of the flask into the separatory funnel. Rinse the used boiling stick with water and discard in the trash. 11) Add 10 mL of ether into the separatory funnel, then stopper and shake the separatory funnel for about 1 min with frequent venting. Mount the separatory funnel back on the ring, remove the stopper and allow the layers to separate. Then drain the lower aqueous layer into a 50-mL Erlenmeyer flask, but leave the upper organic layer in the separatory funnel. At the END of the lab period, discard the aqueous layer down a fume hood sink drain with the water running. 12) Add 10 mL ether followed by 3 mL of 5% aqueous NaOH to the separatory funnel. Stopper and shake the separatory funnel for about 2 min with frequent venting. Remove the stopper and allow the layers to separate. Drain the lower aqueous layer into a small Erlenmeyer flask and test it for acidity/basicity using litmus paper (red litmus paper will turn blue if basic but will remain red if acidic!). If acidic, add 3 mL of 5% NaOH to the organic layer in the separatory funnel and shake the funnel for about 2 min. Remove the stopper, allow the layers to separate, drain the lower layer into an empty Erlenmeyer flask and test it for acidity/basicity using litmus paper. If acidic, repeat washing as before with another 3 mL of 5% NaOH and check the acidity/basicity of the aqueous layer; repeat this until the aqueous layer is basic! At the END of the lab period, discard all aqueous NaOH layers down a fume hood sink drain with the water running. 13) Pour the organic layer from the top opening of the separatory funnel into a dry 50-mL Erlenmeyer flask and dry the organic layer with anhydrous Na2SO4 (about 4 g). Cork the flask, swirl briefly and allow the flask to sit for 10 min. 14) Carefully decant the liquid away from the spent drying agent into a dry 50-mL RB flask for distillation. 15) Rinse the spent drying agent with approx. 5 mL of ether and add the rinse to the RB flask. After the ether rinse, attempt to dissolve the spent drying agent in water with periodic stirring over a period of time as you proceed with the rest of the experiment; the water solution can be discarded down a fume hood sink drain and any undissolved drying agent can be discarded in the trash (don’t discard SOLIDS down the sink drain). 16) Add a boiling stick, assemble a simple distillation apparatus (Fig. 3), and begin to distill the solution. Use a 50-mL Erlenmeyer flask as the receiving flask and set the voltage regulator to 3.5. As the temperature increases, the lower boiling components in the mixture (diethyl ether and any unreacted 1-hexene, etc.) will begin to distill. Allow the distillation to proceed until the thermometer reaches 3 degrees below the boiling point of 2-hexanol. At this point remove the 50-mL Erlenmeyer flask (containing ether and unreacted 1-hexene, etc.) and place a clean and dry pre-weighed 25-mL Erlenmeyer flask. Allow the distillation to proceed until the temperature on thermometer reaches 3 degrees past the boiling point of 2-hexanol. At this point remove the 25-mL Erlenmeyer flask and place another 25-mL Erlenmeyer flask to distill the rest of the solution but do NOT go to dryness!  REVIEW HOW TO PERFORM A SIMPLE DISTILLATION (including how to assemble the apparatus, how and when to collect fractions, etc.)! Do some thinking and planning before you arrive in the lab.  Look up and record the bp ranges of diethyl ether, 1-hexene, trans- and cis-2-hexene, trans- and cis-3-hexene, & 1- and 2hexanols before coming to the lab!  Use clean and dry glassware to set up your distillation apparatus.  As always, record bp ranges, etc. of all distillation fractions collected, and record the weight and appearance of the alcohol product obtained. PLEASE wash the magnetic stir bar and remember to return it as directed by your instructor. WHEN WASHING THE STIR BAR PLEASE BE CAREFUL THAT IT DOES NOT FALL DOWN THE SINK! Figure 3. Fully assembled simple distillation apparatus Vapors will collect in distillation adapter & begin to condense Remaining vapors will liquefy in water-cooled condenser & run down inner tube, through the vacuum (bent) adapter into a receiving vessel Expt. #1 Investigating the Regioselectivity of Unsymmetrical Alkene Hydration: Hydration of 1Hexene Introductory Background Alkenes (cyclic and acyclic) react with H2SO4 and produce alkyl hydrogen sulfates (see generic chemical equation below). When the alkene molecule is structurally unsymmetrical and one of the carbons of C=C is directly bonded to a greater number of hydrogens, the reaction is regioselective (follows Markovnikov’s rule) and leads to a major alkyl hydrogen sulfate accompanied by little or no minor product. e.g. Mechanistically, this reaction involves carbocations as intermediates and carbocation rearrangement (via 1,2-hydride shift or 1,2-methyl shift) may occur during the reaction. e.g. Since the positively charged carbon atoms of carbocations are trigonal planar (sp2 hybridization), syn and anti addition of H and OSO3H across C=C is possible and may lead to stereoisomes. In previous example, A is produced as a racemic mixture of the R and S enantiomers. The OSO3H is a good leaving group and upon reaction with H2O (a weak nucleophile), alkyl hydrogen sulfates are converted to alcohols (SN1 mechanism). e.g. The Experiment – Its Goal You will first react 1-hexene with H2SO4 to form an alkyl hydrogen sulfate. You will subsequently treat the alkyl hydrogen sulfate with H2O and isolate the alcohol product by distillation. You will identify your alcohol product as (R,S)2-hexanol, 1-hexanol or a mixture of both based on the boiling point of your alcohol product. Note: If Markovnikov regioselectivity is followed in your reaction, (R,S)-2-hexanol should be the major product and if not, 1-hexanol should be the product. Note: bp 2-hexanol 136 oC; bp 1-hexanol 156-157 oC What you should write in your lab notebook before coming to the lab 1. Title of experiment 2. Goal of experiment 3. Equations 1 and 2 4. Prepare a table as shown below & write in the appropriate figures for each reactant used and possible organic product(s) FW (g/mol) Density (g/mL) Mass or Volume (g or mL) Number of moles 1-hexene H2SO4 (85%) H2O 2-hexanol/1-hexanol 84.16 98.07 18.02 102.17 0.678 1.78 1.00 0.81/0.814 10 mL 10 mL 30 mL 8.23 g* 0.0806 0.154 1.66 0.0806* ___________________________________________________________ * Theoretical quantities (calculated) 5. Provide the references from which you obtained the information in the table 6. Determine the limiting reagents (LR) for Eq. 1 and Eq. 2 7. Determine the theoretical yield for final organic product(s) from Eq. 2 Note: For this experiment, the information in the table is provided for you but for future experiments you must provide the information! Additional Notes To calculate # of moles of H2SO4 used in this experiment (10 mL 85%w/w) you need to know the density of 85% (w/w) which is 1.78 g/mL (CRC Handbook of Chemistry & Physics)
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