SC CHEM 333 - Reactions of Carbocation’s Post-Lab (3 pages)

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Reactions of Carbocation’s Post-Lab



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Organic Chemistry 333L section 03M Laboratory Post Lab Reactions of Carbocation s By Cameron Kahn 29 October 2013 TA James Collie Observations After Placing 100 mg of triphenylmethanol a white crystalline looking solid into a small test tube no smell observed With the addition of acetic acid 2 mL to the test tube a clear liquid with a slightly sweet vinegar smell was observed With the addition of the acetic acid and heat the triphenylmethanol dissolved and only a clear liquid remained behind This step took about 18 minutes to completely dissolve the solid After the addition of hydrobromic acid HBr a clear liquid the solution turned to a slightly yellow color This could have been due to the test tube not being thoroughly cleaned After a longer period of heating the yellowish solution did appear to get lighter in color The solution was left to stand at room temperature and then placed into an ice bath After an additional 15 minutes a yellowish powder like precipitate formed The yellowish substance was then suction filtered and washed for impurities The observed yellow powder took the form of yellowish crystalline solids and a vinegar like odor was detected Results The Starting value of triphenylmethanol was measured to be 102 mg The initial value of the weighing paper was 121 0 mg After suction filtration and rinsing the product with 3 to 4 drops 1 Page of both cold hexane and deionized water the weighing paper plus the product was measured to be 129 0 mg From the weight by difference method the final product was measured to be 8 0 mg and a calculated percent yield of 6 35 was noted The record melting point of the product was 122 C The melting point percent error was noted to be 79 74 Calculations Net weight of product Weighing Paper and product Weighing paper Net Product 129 mg 121 mg 8 mg Triphenylmethyl bromide Percent product yield triphenymethylbromid 323 23 g 1 mol 1 mol triphenylmethanol 1mol triphenylmethylbromide 0 00039181 mol triphenylmethanol 0 126644874 g triphenylmethylbromide theoretical 100 yield actual 100 theoretical y ield 0 0 8 g 100 6 35 0 126 g Melting point percent error Calculated Melting Point 100 Theoretical Melting Point 122 C x 100 79 74 153 C Conclusions In this experiment he she learned how reactions of carbocations work in respects to acidic solvents and precipitate formation Another learning outcome from this experiment was to effectively dissolve a solid into an acid then isolate the solid from the liquid solution and then calculate the products melting point After the experiment had ended the amount of product yielded was unexpectedly low and could be due to the transfer of the product from one test tube to another and then when the product was dumped into the suction filtration apparatus In addition the color of the final product should have been a crystalline white product but with one of the test tubes not being cleaned and thoroughly dried the final product had a yellow tent Analysis of IR NMR No IR NMR completed for this experiment One could infer however that if there was an IR analysis done one would see a possible O H group at around 3450cm 1 and most likely a phenyl 2 Page group around 3400cm 1 The acetic acid peak would be somewhere around the 1700cm 1 wavelength And it is likely if an IR were to be done that one would see sp3 hybridized carbons somewhere around the 3000 cm 1 wavelength However due to some human error in maybe the proper cleaning of the test tubes the IR will show some flaws and will not be 100 percent reliable References 1 Ali George Handy and Salman Essentials of Organic Chemistry Montgomery AL 36117 QDE Press 2012 2 Jencks William P When Is an Intermediate Not an Intermediate Enforced Mechanisms of General Acid base Catalyzed Carbocation Carbanion and Ligand Exchange Reaction Accounts of Chemical Research ACS Publications N p n d Web 27 Oct 2013 3 Page


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