Presentation on theme: "MONDAY LAB: Experiment 10 E2 ELIMINATION OF 2-BROMOHEPTANE:"— Presentation transcript:
1 GUIDED-INQUIRY PROJECTS AND EXPERIMENTS CHRISTINA NORING HAMMOND VASSAR COLLEGE POUGHKEEPSIE, NY
2 MONDAY LAB: Experiment 10 E2 ELIMINATION OF 2-BROMOHEPTANE: INFLUENCE OF THE BASEQUESTION: What effect does the bulkiness of the base have on the productcomposition in the E2 debromination of 2-bromoheptane?• Microscale procedure• Students work in teams of two with one using each base.• Product composition determined by GC analysis.
3 EXP. 8.1: RADICAL CHLORINATION REACTIONS QUESTION: Do statistical factors determine the product composition in radical chlorination reactions or do electronic factors play a role?• Green Chemistry: Cl2 is generated in situ from household bleach (5.25% NaOCl)and 3 M HCl:• Substrates used:• Microscale experiment.• Teamwork.• Irradiation with 300-watt unfrosted incandescent bulb until the yellow colorof Cl2 disappears (~5 min).• Product mixture analyzed by GC.
4 EXP 8.2: PHOTOBROMINATION OF 1,2-DIPHENYLETHANE QUESTION: Which diastereomer forms in the photobromination of1,2-diphenylethane?• Green Chemistry: Bromine is generated in situ:• Irradiation done with 100-watt incandescent bulb for ~10 min.• Product analyzed by m.p.
5 PROJECT 6: E1/E2 ELIMINATION REACTIONS QUESTION: Compare the mixture of isomeric alkenes produced by an acid-catalyzed dehydration and a base-catalyzed dehydrochlorination.Are the product ratios influenced primarily by product stability?• Two-week project for a team of two students.
6 PROJECT 6: E1/E2 ELIMINATION REACTIONS Project 6.1 Acid-Catalyzed Dehydration of 2-Methyl-2-butanolQUESTION: Does product stability or do statistical factors determine the ratioof 2-methyl-2-butene to 2-methyl-2-butene?Project 6.2 Synthesis of 2-Chloro-2-methylbutanePURPOSE: To synthesize 2-chloro-2-methylbutane for use in adehydrochlorination reaction.
7 PROJECT 6: E1/E2 ELIMINATION REACTIONS Base-Catalyzed Dehydrochlorination of 2-Chloro-2-methylbutaneQUESTION: Does product stability or do statistical factors determine the ratioof 2-methyl-2-butene to 2-methyl-2-butene?• Both students run the reaction using product prepared in 6.2.
8 Project 4 INTERCONVERSION OF 4-tert-BUTYCYCLOHEXANOL AND 4-tert-BUTYCYCLOHEXANONEQUESTION: What is the stereoselectivity of NaBH4 reduction of4-tert-butylcyclohexanone?Project 4.1Green Chemistry: Sodium Hypochlorite Oxidation of 4-tert-Butylcyclohexanol• Rate of reaction dependent on rate of stirring.• When is the reaction complete?• Reaction monitored by TLC analysis using p-anisaldehyde visualization.
9 INTERCONVERSION OF 4-tert-BUTYCYCLOHEXANOL AND 4-tert-BUTYCYCLOHEXANONEProject 4.2Sodium Borohydride Reduction of 4-tert-Butylcyclohexanone• Reaction can be monitored by TLC.• Product analysis by GC and/or NMR.-trans isomer: axial proton on C with --OH at 3.5 ppm.-cis isomer: equatorial proton at 4.03 ppm.
10 PROJECT 12: BIOCHEMICAL CATALYSIS AND THE STEREOCHEMISTRYOF BOROHYDRIDE REDUCTIONQUESTION: What the stereoselectivity in the sodium borohydride reduction ofbenzoin to 1,2-diphenyl-1,2-ethanediol?PROJECT 12.1• Green Chemistry: Traditional catalyst, KCN, is replaced with thiamine.• Benzoin condensation is first step in a three-step project.
11 PROJECT 12: BIOCHEMICAL CATALYSIS AND THE STEREOCHEMISTRYOF BOROHYDRIDE REDUCTIONPROJECT 12.2• Cyclic acetal analyzed by NMR.
12 PROJECT 12: BIOCHEMICAL CATALYSIS AND THE STEREOCHEMISTRYOF BOROHYDRIDE REDUCTION• NMR analysis by chemical shifts of the -CH3 groups and the methine protons.
13 PROJECT 14: SUGARS: GLUCOSE PENTAACETATES QUESTIONS: What is the relative stability of - and -D-glucose pentaacetate?How can you distinguish between kinetic and equilibrium controlin the synthesis of the glucose pentaacetates?PROJECT 14.1 Synthesis of - and -D-Glucose Pentaacetate
14 PROJECT 14: SUGARS: GLUCOSE PENTAACETATES PROJECT Investigation of Kinetic and Equilibrium Control in theGlucose Pentaacetate System• PRELABORATORY ASSIGNMENT: Analyze NMR spectra of both crudeand recrystallized - and -D-glucose pentaacetates.• C-1 (anomeric) protons: - glucose, 6.33 ppm; - glucose, 5.72 ppm.• Determine ratio of - and -D-glucose pentaacetate in each sample.• Are the recrystallized samples at least 95% pure?• Design a set of experiments to investigate the equilibration of - and-D-glucose pentaacetates.• Students are given two isomerization methods to use for the tests.• NMR analysis of all products.
15 PROJECT 14: SUGARS: GLUCOSE PENTAACETATES PROJECT Computational Chemistry Experiment• In aq. solutions of -glucose anomer, the C-1 hydroxyl group is equatorialand with the-glucose anomer, the C-1 hydroxyl group is axial.• Build models of axial- and equatorial-isomers of:• Calculate heats of formation for each isomer.• Use difference in heats of formation for the 2-acetoxytetrapyran conformersto calculate Keq for - and -D-glucose pentaacetate.• Are your calculations consistent with your investigations of kinetic andequilibrium control in the glucose pentaacetate system?
16 ACKNOWLEDGEMENTS • Paul F. Schatz, University of Wisconsin • Colleagues and students at Vassar and Carleton• Jhong Kim, UC Irvine• My many Vassar student assistants• W. H. Freeman and Co, publishers
19 PROJECT 9: BROMINATION OF CYCLOHEX-4-ENE-cis-1,2-DICARBOXYLIC ACIDQUESTION: What is the stereochemistry of bromine addition to the double bond?• A three-step synthesis project.• First step: Diels-Alder synthesis and subsequent hydrolysis of anhydride.• Pyridinium tribromide is the source of Br2.• Dimethyl ester is subsequently prepared and stereochemistry determined by NMR.
20 PROJECT 9: BROMINATION OF CYCLOHEX-4-ENE-cis-1,2-DICARBOXYLIC ACID anti Addition of Bromine: Bromonium ion pathway.syn Addition of Bromine: Carbocation pathway.
21 TUESDAY LAB GREEN CHEMISTRY: SYNTHESIS AND HYROGENATION OF SUBSTITUTED CHALCONES A GUIDED-INQUIRY PROJECTQUESTION: Which functional groups are reduced in the hydrogenationof a polyfunctional molecule?Part 1Synthesis of the Chalcone• Use concentrated aqueous NaOH solution for reaction.• Product recrystallized from 95% ethanol.• Product analyzed by IR and NMR.Reference: Palleros, D. R. J. Chem. Educ. 2004, 81, 1345–1347.
22 GREEN CHEMISTRY: SYNTHESIS AND HYROGENATION OF SUBSTITUTED CHALCONES A GUIDED-INQUIRY PROJECTPart 2Hydrogenation of the Chalcone• Determine a suitable TLC solvent for the chalcone.• Completion of reaction determined by TLC analysis.• Product analyzed by TLC, IR, NMR, and GC-MS.