Lecture 8!!Chem 237 March 10, 2015What are you going to do this week?Attempt the double dehydration of pinacol this week Heat 2,3-dimethyl-2,3-butanediol with 3 M H2SO4 Distill the product off with a simple distillation set-up Wash the organic product in sep funnel with water and the saturated NaCl solution (know which layer is which). May need to add methylene chloride if bad emulsion or only one layer Stop Here Next week Fractionally Distill the Product Determine product structure and characterize by NMR and IR (also boiling point).Exam next week during class!Exam room will be announced by email and on Compass website Coverage: Experiments 1-4 (NMR) and Lecture Material (details to follow)Material on Exam 1Synthesis, Reactions, and Reaction Conditions, and Associated Experimental Techniques ✔Isolation of BC Powder • Multiple techniques (see next slide) ✔Banana Oil - Acid-Catalyzed Esterification • Pushing an equilibrium by removal of product ✔Diels-Alder Cycloaddition – Isolation of a Conjugated Diene from Eucalyptus Oil • Formation of a derivative to establish structure ✔NMR Dry lab • Technique for structure elucidationMaterial on Exam 1Methods for Product Isolation ✔Crystallization • Precipitation or crystallization of product ✔Simple distillation • How to set up apparatus and perform distillation • Principle of technique ✔ Working up a reaction •Extraction of salts/H2O soluble materials •Drying with Mg2SO4Material On Exam 1Methods for Product Purification ✔Extraction • Taking advantage of acid/base chemistry, flow charts, etc. ✔Fractional Distillation • Phase diagrams • Differences from simple distillation • Azeotropes ✔Recrystallization • Theory and practice – supersaturated solution, solvent selection, hot filtration, etc.Material on Exam 1Methods for Product Analysis ✔Melting point • Principles of technique • How to obtain a melting point ✔TLC • Principles of technique • How to run a TLC • Variables that can be altered (ie., polarity of solvent) ✔IR • Theory • Assigning a spectra (you should know common functional groups) ✔NMR • Theory • Assigning spectra (you should know common functional groups) • Using NMR to identify a compound ✔Chromatography (column) • Principles of technique • Solvent and compound polarity, etc.Format of Exam 11. Separation and Product Isolation 2. Purification and purity analysis methods 3. Chemistry – Reactions 4. Spectroscopy Theory 5. Structure Elucidation Molecular Formula IR, 1H-NMR, 13C-NMR spectra Three Spectroscopic Data Graphs – all the data you need Questions are all based on: Your laboratory experiments My lectures The textbook (lesser extent)Guidelines and Tips 1H NMR peaks – label using letters (a, b, c, etc.), starting with the peak that is the most downfield (highest ppm). 13C NMR peaks – label using numbers (1, 2, 3, etc.), starting with the peak that is most downfield (highest ppm). ! Don’t mistake residual solvent peaks or the TMS peak for a signal (peak) from the sample. 1H NMR: singlet at 7.26 ppm due to residual CHCl3 from CDCl3 (solvent); singlet at 0 ppm due to TMS. 13C NMR: three peaks of equal intensity at 77.16 ppm due to CDCl3 (solvent); singlet at 0 ppm due to TMS!Chemical shifts (δ) – report as center of the peak set. For peaks with odd multiplicities (triplet, quintet, etc.), the chemical shift is that of the middle peak. For peaks with even multiplicities (doublet, quartet, etc.), the chemical shift is reported as the average of the two central most peaks. ! The coupling constant (J) – equal to the distance, in Hz, between adjacent peaks in a multiplet. Integral values are proportional to the number of hydrogens represented by a given peak. A broad singlet - a hydrogen attached to an electronegative atom (-OH, -NH2, etc.) – exchange broadening. Hydrogens on electronegative atoms (-OH, -NH2, etc.) often show no coupling to neighboring hydrogens – exchange decoupling.Use abbreviations for multiplets. singlet (s) sextet (sext) doublet (d) septet (sept) triplet (t) octet (oct) quartet (q) nonet (non) quintet (quint) multiplet (m) ! Degrees of unsaturation (DOU) is calculated as: where C is the number of carbons, H the number of hydrogens, N the number of nitrogens X the number of halogens.DOU =2C + 2 − H + N − X213C NMR• I = ½ Two spin states α and β• 13C Chemical Shift range δ 0-200 (vs. 1H δ 0-12) • 1H-13C couple, but 1H is decoupled • All 13C signals are singlets! • Integrations are not accurate – the more H’s the larger the signal quaternary C’s – very weak13Characteristics of 13C NMR Signal weak (need more scans) No C-C coupling (this helps!) Strong C-H coupling (this doesn’t help!) Large chemical shifts (0 - 220 ppm)13C Nuclear Magnetic ResonanceProton Coupled 13C NMR (CMR)ppmProton Decoupled 13C NMRppm0 – 35 ppm15 – 40 ppm25 – 50 ppm25 – 70 ppm65 – 90 ppm100 – 150 ppm110 – 175 ppm190 – 220 ppm ppm from TMSReference solvent: CHCl3triplet, 77 ppmChemical Shifts for 13C NMRCq’s are very small!Integration (peak height or area) is NOT proportional to number of carbon atoms!Integration is different from 1H NMRTo a first approximation, assignments based primarily on chemical shift12341234Table of Common 13C NMR Chemical ShiftsTable of Common 13C NMR Resonances020406080100120140160180200220ketonealdehydecarboxylic acidester, amideheteroaromatic, -C=N-heteroaromatic, -C=C-nitrile, -CNaromatic, -C=C-alkenealkyne3° alcohol, ether2° alcohol, etheramine, -C-Namine, -CH-Nmethyl alcohol, etheramine, -CH2-N1° alcohol, etherhalide, -C-Xhalide, -CH-X3° alkyl4° alkyl2° alkylamine, CH3-N1° alkylhalide, -CH2-Xhalide, -CH3-Xppm from TMS!!!!!!! ppm from TMSTable of Common IR FrequenciesTable of Common IR Frequencies500750100012501500175020002250250027503000325035003750alcohol, OH (s, str)alkyne, CH (s, str)amine, NH (m, str)aromatic, CH (m, str)alkene, CH (m, str)alkane, CH (s, str)carboxylic acid, OH (s, str)aldehyde, CH (w, str)nitrile, CN (s, str)alkyne, CC (s, str)ester, C=O (s, str)carbonyl (s, str)alkene, CC (m, str)aromatic, C=C (s, str)amine, NH (s, bend)alkane, CC (m, var)nitro, NO (s, str)phenol, CO (s, bend)3° alcohol, CO (s, str)amine, CN (m, str)2° alcohol, CO (s, str)ether, CO (s, asym str)1° alcohol, CO (s, str)ester, CO (s, asym str)trans-alkene, RC=CR (m, bend)alkyne, CH (m, bend)amine,