Lecture 8 Chem 237 March 10 2015 What 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 1 Synthesis 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 elucidation Material on Exam 1 Methods 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 Mg2SO4 Material On Exam 1 Methods 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 1 Methods 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 1 1 2 3 4 5 Separation and Product Isolation Purification and purity analysis methods Chemistry Reactions Spectroscopy Theory Structure Elucidation Molecular Formula IR 1H NMR 13 C 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 H NMR peaks label using letters a b c etc starting with the peak that is the most downfield highest ppm 1 C NMR peaks label using numbers 1 2 3 etc starting with the peak that is most downfield highest ppm 13 Don t mistake residual solvent peaks or the TMS peak for a signal peak from the sample 1 H NMR singlet at 7 26 ppm due to residual CHCl3 from CDCl3 solvent singlet at 0 ppm due to TMS 13 C NMR three peaks of equal intensity at 77 16 ppm due to CDCl3 solvent singlet at 0 ppm due to TMS Chemical shifts 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 septet sept triplet t octet oct quartet q nonet non quintet quint multiplet m doublet d 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 2C 2 H N X DOU 2 13 I 13 C NMR Two spin states and C Chemical Shift range 0 200 vs 1H 1 13 0 12 1 H C couple but H is decoupled All 13 C signals are singlets Integrations are not accurate the more H s the larger the signal quaternary C s very weak 13C Nuclear Magnetic Resonance 13 Characteristics 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 Proton Coupled 13C NMR CMR ppm Proton Decoupled 13C NMR ppm Chemical Shifts for 13C NMR ppm from TMS 0 35 ppm 65 90 ppm 15 40 ppm 100 150 ppm 25 50 ppm 110 175 ppm 25 70 ppm Cq s are very small 190 220 ppm Reference solvent CHCl3 triplet 77 ppm Integration is different from 1H NMR Integration peak height or area is NOT proportional to number of carbon atoms 4 3 2 4 3 1 2 1 To a first approximation assignments based primarily on chemical shift Table of Common 13C NMR Chemical Shifts Table of Common 13C NMR Resonances halide CH3 X halide CH2 X 1 alkyl amine CH3 N 2 alkyl 4 alkyl 3 alkyl halide CH X halide C X 1 alcohol ether amine CH2 N methyl alcohol ether amine CH N amine C N 2 alcohol ether 3 alcohol ether alkyne alkene aromatic C Cnitrile CN heteroaromatic C Cheteroaromatic C Nester amide carboxylic acid aldehyde ketone 220 200 180 160 140 120 100 ppmfrom from TMS ppm TMS 80 60 40 20 0 Table ofTable Common IR Frequencies of Common IR Frequencies cis alkene RC CR m bend Vibrational Modes Vibrational Intensities amine NH s bend str stretching bend bending sym symmetric asym asymmetric s strong m medium w weak alkyne CH m bend trans alkene RC CR m bend ester CO s asym str 1 alcohol CO s str ether CO s asym str 2 alcohol CO s str amine CN m str 3 alcohol CO s str phenol CO s bend nitro NO s str alkane CC m var amine NH s bend aromatic C C s str alkene CC m str carbonyl s str ester C O s str alkyne CC s str nitrile CN s str aldehyde CH w str carboxylic acid OH s str alkane CH s str alkene CH m str aromatic CH m str amine NH m str alkyne CH s str alcohol OH s str 3750 3500 3250 3000 2750 2500 2250 2000 Wavenumbers cm 1 1750 1500 1250 1000 750 500 Ester C O stretch at 1743 cm 1 Alkyl C H stretch 3 000 cm 1 Acid C O stretch at 1712 cm 1 Broad O H stretch carboxylic acid Alkenyl C C at 1 661 cm 1 Two N H stretches 3 000 cm 1 Alkenyl C H stretch 3 000 cm 1 Terminal alkene C H bend at 888 cm 1 Integrated Spectroscopy Problem 6 15 pts An unknown molecule exhibits a high resolution EI MS exact mass of m z 188 1058 molecular ion Its IR