NMR = Nuclear Magnetic Resonance
|
|
- Albert Cecil Harrington
- 6 years ago
- Views:
Transcription
1 NMR = Nuclear Magnetic Resonance NMR spectroscopy is the most powerful technique available to organic chemists for determining molecular structures. Looks at nuclei with odd mass numbers or odd number of protons: 1 H, 13 C, 15 N, 19 F, 31 P
2 NMR spectroscopy that is looking at 1 H nuclei is called proton NMR or 1 H-NMR. If you just say NMR, it will generally be assumed you re talking about proton NMR. NMR looking at 13 C nuclei is called 13 C-NMR. Nuclei with odd mass numbers or number of protons have nuclear spin states. Spinning nuclei generate magnetic fields.
3 Spinning nuclei will line up with or against an external magnetic field (B 0 ). Aligned with the field Aligned against the field
4 Alignment with the field (lower energy) is called the spin state. Alignment against the field (higher energy) is called the spin state. The difference in energy between and : E. In the absence of an external magnetic field, orientations are random. Application of the external field forces nuclei into the or spin states. B 0 E no external field
5 A photon of the correct energy ( E) can cause flipping from the spin state to the spin state. When flipping occurs, the energy of that photon is absorbed. When the combination of the external magnetic field strength and photon energy produce flipping, the nucleus is in resonance with the magnetic field and that frequency of electromagnetic radiation. E is proportional to the external magnetic field strength. E = h B 0 2 where B 0 is measured in gauss and is the gyromagnetic ratio unique for each kind of nucleus
6 E = h B 0 2 For a proton, = 26,753 sec 1 gauss 1 Since E = h Factoring out h, gives h = h B 0 2 = 1 B 0 2 The frequency ( ) and field strength (B 0 ) are directly proportional.
7 = 1 B 0 2 This equation tells us that for a frequency of 60 MHz (radio frequency or RF), a magnet with a strength of 14,092 gauss is needed for resonance with a bare proton (H nucleus). A radio frequency of 300 MHz requires a magnet 5x stronger (70,459 gauss) for resonance with a bare proton.
8 But nuclei in molecules are not bare, isolated nuclei they are surrounded by clouds of electrons. In the presence of an external magnetic field, an electron cloud has an induced magnetic field that opposes the external field. This means it takes a stronger external field to get resonance a stronger field is needed because the electron cloud effectively shields the nucleus. The effective magnetic field experienced by the nucleus is the strength of the external field minus the shielding effect. B effective = B external B shielding
9 The electron cloud density (and thus shielding) is different for different nuclei due to different chemical environments (magnetic environments). more shielded protons requiring higher field strength to get resonance at a specific H H C H.. O : H less shielded proton due to electron withdrawing effect of electronegative oxygen requiring lower field strength to get resonance at a specific The differences in shielding mean that the we can detect the differences in the chemical environments of the nuclei in an NMR spectrometer.
10 NMR spectrometer: RF is held constant common frequencies are 60 MHz, 100 MHz, and 300 MHz. Magnetic strength is varied
11 downfield upfield increasing magnetic field strength
12 Chemical shift Chemical shift for protons = the difference between magnetic field strength needed for resonance of a given proton and the magnetic field strength needed for resonance of a proton in tetramethylsilane (TMS). CH 3 H 3 C Si CH 3 CH 3 Due to the low electronegativity of the central silicon atom, protons in TMS are more shielded than any other protons likely to show up in organic compounds. Proton signals in most organic compounds will therefore be shifted downfield from TMS (i.e. require weaker fields for resonance).
13 The amount of downfield shifting from TMS is expressed in Hz and is divided by the radio frequency of the instrument. (Even though NMR spectrometers vary magnet strength, remember that frequency is proportional to magnetic field strength.) chemical shift = shift downfield from TMS in Hz instrument frequency in MHz Since Hz units cancel, the chemical shift is unitless. Since MHz are 1,000,000 times Hz, the amount of chemical shift is called parts per million (ppm). The chemical shift is symbolized by (delta scale).
14 The advantage of expressing chemical shift data on the delta scale is that it is easily allows for the comparison of data from instruments that are operating at different field strengths.
15 The higher field strength instruments are used because they give higher resolution and higher sensitivity. The main drawbacks to the higher field strength instruments are initial cost and very high maintenance cost.
16 300 MHz NMR spectrum of methanol: Ultimately, the number of signals indicates the number of different chemical environments in the molecule.
17 Since the number of signals is related to how many different chemical environments are present in a molecule, it is useful to be able to recognize groups of chemically equivalent protons. How many groups of chemically equivalent protons are present in each of the following compounds. Hint: Think about symmetry. CH 3 NO 2 CH 3 -CH 2 -CH 2 -Br CH 3 O If different chemical shifts are so close that the signals cannot be resolved, the protons are called accidentally equivalent. Accidental equivalence can only be determined experimentally.
18 Diastereotopic protons are in different chemical environments (i.e. are not chemically equivalent) and therefore give different chemical shifts (may only resolve in 300 MHz instrument). Diastereotopic protons are identified by seeing if you get diastereomers by replacing them. Are these protons chemically equivalent? H H CHO H OH CH 2 OH imagine replacing each with Br or some other atom Br H CHO H OH CH 2 OH H H CHO Br OH CH 2 OH What is the relationship between these two structures?
19 Are these protons chemically equivalent? H H Cl imaginary replacement Br H Cl H Br Cl R enantiomer S enantiomer Replacement did not produce diastereomers, therefore the chemical environments are the same. Therefore both protons will give the same chemical shift. The protons in question are enantiotopic protons which are chemically equivalent. NMR can not distinguish enantiomer.
20 How many groups of chemically equivalent protons are present in the following compounds? OH H CH 2 CH 2 CH 3 H H
21 Again, different protons have different expected chemical shifts depending upon their different chemical environments. X in CH 3 -X F OH Cl Br I EN CH 3 -CH 2 -CH 2 -CH 3 CH 3 -CH 2 -CH 2 -CH 2 -Br = deshielding caused by nearby Br =
22 Typical Values of Chemical Shifts (see Table 13-3) Type of proton Approximate Type of proton Approximate alkane CH Ph-H 7.2 alkane CH Ph-CH alkane CH 1.4 R-CHO 9-10 O -C-CH R-COOH C C H R-CH 2 -X (X = halogen, O) C C 5-6 H C C 1.7 CH R-OH variable, about Ar-OH variable, about 4-7 R-NH 2 variable, about R-CH 2 -NH 2 2.6
23 Predict the expected chemical shifts of the following groups of chemically equivalent protons. CH 3 CH 3 Chemical shift values are approximately additive when you predict chemical shifts you need to take into account additive effects. CH 2 CH 3 O CH 2 CH 3
24 Groups on a benzene ring can cause downfield or upfield shifts depending upon whether the group is electron withdrawing or electron donating. NO 2 OMe OMe O
25 Origins of chemical shifts In some cases, electron withdrawing effects cause deshielding (and electron donation causes more shielding). Ex. CH 3 -CH 2 -CHO CH 3 -CH 2 - NO 2 In other cases, shielding and deshielding are caused by magnetic effects of nearby pi systems
26 = 7.2
27 = 5-6
28 = 2.5
29 Aldehyde protons are strongly deshielded by a combination of electron withdrawing and magnetic effects. = 9-10
30 Carboxylic acid protons are very strongly deshielded due to being attached to an O which is attached to an electron-withdrawing C=O. ( = 10 12) What else can you say about the compound that gave the above spectrum?
31 Peak area related to number of protons in a given chemical environment. Indicated by an integral trace on NMR spectrum. (height of trace is proportional to peak area) (peaks with bigger areas are usually taller) a b c a d 6 spaces total 0.5 d c b 3.0 a Ratio of protons - a:b:c:d = 3.0 : 1.5 : 1.0 : 0.5 To get whole numbers multiply by 2 to get: 6 : 3 : 2 : 1
32 a b c a d 6 spaces total 0.5 d c b 3.0 a A ratio of 6 : 3 : 2 : 1 could represent a compound with a total of 12 H s ( = 12) or Any compound with the same ratio and a multiple of 12 H s Ex. 12 : 6 : 4 : 2 ratio for a total of 24 H s
33 a b c a d 6 spaces total 0.5 d c b 3.0 a Or if total number of H s is known to start with, figure out how many spaces = 1 H (You have a molecular formula.) 6 spaces = 12 H s means 0.5 spaces = 1 H The integral with 3 spaces then represents 6 H s giving that signal.
34 a b c a d 6 spaces total 0.5 d c b 3.0 a Integral traces are not always this neat and well-defined. Sometimes deciding where traces start and end is tricky may require some trial and error to get ratios that make sense.
35 Insert NMR with integration curve and have class determine ratio on a handout.
36 Spin-Spin Splitting Signals of protons often do not show up as single peaks their signal can be split by magnetically coupled protons. Because a proton we re interested in may be near other protons, the magnetic fields of those nearby protons can reinforce (add to) or oppose (subtract from) the external magnetic field shifting a signal downfield or upfield. Downfield shift due to one adjacent proton adding to field strength Upfield shift due to one adjacent proton subtracting from field strength Expected signal location
37 The more magnetically coupled protons there are, the more complex splitting gets because all adjacent protons could be spinning in the same direction, all adding or all opposing the external field or some could be spinning in opposite directions giving mixed effects. Ultimately, this splitting will tell you the number of protons on adjacent carbons. Notice that the peak area ratios reflect the number of combinations that cause each peak
38 The splitting pattern ultimately follows an N + 1 Rule: N equivalent coupled protons split a signal into N + 1 peaks. N Number of peaks (multiplicity) Relative peak areas 0 1 (singlet) (doublet) 1 : (triplet) 1 : 2 : (quartet) 1 : 3 : 3 : (quintet) 1 : 4 : 6 : 4 : (sextet) 1 : 5 : 10 : 10 : 5 : (septet)
39 Most splitting is caused by adjacent protons. Ph-CH 2 -CH 3 These protons should split each other s signals splitting is reciprocal. Some splitting is caused by protons on the same carbon (only if diastereotopic). H CH 2 CH 2 CH 3 These protons will split each other s signal H H Splitting by protons separated by a total of 4 or more bonds is normally not observed (but there are exceptions) 1 H H C C C Too far away to be magnetically coupled
40 Characteristic splitting patterns to know: Peaks representing magnetically coupled protons often lean toward one another. Pattern for isopropyl group Pattern for p-disubstituted benzene (1 withdrawing group, 1 donating group)
41 Coupling constants (J) how much proton signals split each other. The magnitude of the J value is also reciprocal.
42 Areas of the NMR Spectra can be expanded to show greater detail. Below it is easier to measure the value of thecoupling constant in the expanded view.
43 Assign the proton signals in the following spectrum of 4,4-dimethylcyclohe-2-en-1-one.
44 Complex splitting When a signal is split by two or more protons that have different coupling constants, the pattern of the peaks no longer follows an N + 1 rule.
45 H a H c H b Protons a and b are trans with coupling constant (J ab ) = 17 Hz Protons a and c are cis with J ac = 11 Hz You can draw a splitting tree to show the expected pattern of peaks for the signal of proton a starting with the biggest split.
46 H a H c H b Protons a and b are trans with coupling constant (J ab ) = 17 Hz Protons b and c are geminal with J bc = 1.4 Hz
47 Label each set of peaks in the NMR spectrum with the letter of the corresponding protons in the following structure: a H 3 C C a H 3 O CH C b OH c
48 Label the groups of protons in the structure below with the letter corresponding to the peak in the NMR spectrum associated with those protons: O d O e a b c
49 Determine the structure for a compound with a formula of C 9 H 10 O 2 if an IR spectrum shows a strong peak at 1705 cm 1.
50 Determine the structure for a compound with a formula of C 9 H 10 O 2 if an IR spectrum shows a strong peak at 1735 cm 1.
51 Determine the structure for a compound with a chemical formula of C 5 H 11 Cl given the following NMR spectrum:
52 Determine the structure for a compound with the chemical formula C 4 H 10 O given the below NMR spectrum:
53 Exchangeable protons: Some protons are exchangeable they come off the atom to which they are attached and can be replaced with a proton from another molecule or the solvent. R-COOH R-OH R-NH 2 R-CONH 2 The proton of an alcohols rapidly exchanges in water or weakly acidic solutions giving a single peak no splitting. Splitting is observed in ultra-pure alcohols (but not always). Moderate exchange gives a broadened peak. Protons on N often show broadened peaks. You generally will not see spin-spin splitting from protons that are attached to O or N.
54 Deuterium Exchange: Peaks that are do to OH or NH protons can be identified by exchange with deuterium. Deuterium is not observed in the 1H NMR spectra. Shaking a sample containing an exchangeable proton with D 2 O causes the exchangeable proton to be replaced by deuterium. And as a result the signal for the exchangeable proton disappears from the spectrum. R-OH + D 2 O R-OD + H-O-D R-NH D 2 O R-ND D-O-H
55 13 C-NMR Signal is weaker because: a) gyromagnetic ratio is only about 1/4 th that of a proton, and b) only about 1% of C s in a compound are 13 C. To obtain a 13 C NMR spectrum hundreds of spectra have to be averaged to get a good signal to noise ratio. FT-NMR allows hundreds of spectra to be taken in a hour or two computer converts free induction decay signal (transients) to an NMR spectrum. (Lower gyromagnetic ratio means radiofrequencies used are lower 75.6 MHz and 15.1 MHz vs. 300 MHz and 60 MHz)
56 Chemical shifts in 13 C-NMR TMS is still used as the reference standard. Chemical shifts are times larger than for a proton on the corresponding C. Ex: CH 3 -OH H has a of 3-4 ppm for CH 3 -OH C has a of ppm CHO H has 9-10 CHO C has
57 This chart will be given on the test but multiplying proton shift values by probably just as useful.
58 The acquisition of 13 C NMR is more complex than 1 H NMR. Each of the protons on a carbon are spin-spin coupled to that carbon, which results in splitting of the carbon signal. Splitting by adjacent 13 C s is not observed because of the low natural abundance of 13 C. Splitting of the carbon signal by the protons attached to the carbon can be used to identify the type of carbon that is responsible for a particular peak. However, proton splitting does complicate the 13 C spectrum. To eliminate the proton coupling, 13 C NMR are generally run decoupled. Spin decoupling of the protons involves irradiation of the sample with broadband rf noise at the proton resonance frequency. This causes rapid proton flipping which averages out their magnetic effects. An added benefit of running a proton decoupled spectrum is that the energy put into the proton from the decoupler is transferred to the carbons causing a change in the distribution of the alpha and beta spin states. This ultimately result in an enhancement of the carbon signal. (less time to get the spectrum)
59 Two decoupling protocols: Proton-spin decoupling removes splitting effect of protons completely. All peaks are singlets (most common). Off-resonance decoupling noise removes splitting effect of all but the protons directly attached to the C. Number of peaks follows an N + 1 where N = number of protons directly on the C not adjacent as in 1 H-NMR.
60 (t) (q) (s) (q)
61 Interpreting 13 C-NMR 1. Number of peaks = number of kinds of C s. 2. Chemical shifts indicate functional groups containing the C s. 3. Splitting pattern in off-resonance decoupled spectra indicate how many H s are attached to the C s. 4. Peak areas only indicate numbers of C s in some types of experiments.
62 CH 3 -CH 2 -CH 2 -CH 2 -CH 2 -Cl
63 O CH 3 -C-CH 2 -CH 2 -O-CH 2 -CH 3
64 C9H10O2
65 Given the following three spectra, determine the structure of the compound.
66
67 Assign peaks in the final structure.
68 Given the following three spectra, determine the structure of the compound.
69
70 Assign peaks in the final structure.
Nuclear Magnetic Resonance Spectroscopy: Tools for Structure Determination
Nuclear Magnetic Resonance Spectroscopy: Tools for Structure Determination Chung-Ming Sun Department of Applied Chemistry National Chiao Tung University Hualien 300, Taiwan Introduction NMR (Nuclear Magnetic
More informationChapter 13 Nuclear Magnetic Resonance Spectroscopy
Organic Chemistry, 6 th Edition L. G. Wade, Jr. Chapter 13 Nuclear Magnetic Resonance Spectroscopy Jo Blackburn Richland College, Dallas, TX Dallas County Community College District 2006, Prentice Hall
More informationChapter 15 Lecture Outline
Organic Chemistry, First Edition Janice Gorzynski Smith University of Hawaii Chapter 5 Lecture Outline Introduction to NMR Two common types of NMR spectroscopy are used to characterize organic structure:
More informationChapter 14. Nuclear Magnetic Resonance Spectroscopy
Organic Chemistry, Second Edition Janice Gorzynski Smith University of Hawai i Chapter 14 Nuclear Magnetic Resonance Spectroscopy Prepared by Rabi Ann Musah State University of New York at Albany Copyright
More informationQuímica Orgânica I. Nuclear Magnetic Resonance Spectroscopy (I) Ciências Farmacêuticas Bioquímica Química AFB QO I 2007/08 1 AFB QO I 2007/08 2
Química Orgânica I Ciências Farmacêuticas Bioquímica Química AFB QO I 2007/08 1 Nuclear Magnetic Resonance Spectroscopy (I) AFB QO I 2007/08 2 1 Adaptado de: Organic Chemistry, 6th Edition; L. G. Wade,
More information4) protons experience a net magnetic field strength that is smaller than the applied magnetic field.
1) Which of the following CANNOT be probed by an spectrometer? See sect 16.1 Chapter 16: 1 A) nucleus with odd number of protons & odd number of neutrons B) nucleus with odd number of protons &even number
More informationThe Use of NMR Spectroscopy
Spektroskopi Molekul Organik (SMO): Nuclear Magnetic Resonance (NMR) Spectroscopy All is adopted from McMurry s Organic Chemistry The Use of NMR Spectroscopy Used to determine relative location of atoms
More information16.1 Introduction to NMR Spectroscopy. Spectroscopy. Spectroscopy. Spectroscopy. Spectroscopy. Spectroscopy 4/11/2013
What is spectroscopy? NUCLEAR MAGNETIC RESONANCE (NMR) spectroscopy may be the most powerful method of gaining structural information about organic compounds. NMR involves an interaction between electromagnetic
More information4) protons experience a net magnetic field strength that is smaller than the applied magnetic field.
1) Which of the following CANNOT be probed by an spectrometer? See sect 15.1 Chapter 15: 1 A) nucleus with odd number of protons & odd number of neutrons B) nucleus with odd number of protons &even number
More informationNMR Spectroscopy. Chapter 19
NMR Spectroscopy Chapter 19 Nuclear Magnetic Resonance spectroscopy is a powerful analytical technique used to characterize organic molecules by identifying carbon-hydrogen frameworks within molecules.
More informationCHEM Chapter 13. Nuclear Magnetic Spectroscopy (Homework) W
CHEM 2423. Chapter 13. Nuclear Magnetic Spectroscopy (Homework) W Short Answer 1. For a nucleus to exhibit the nuclear magnetic resonance phenomenon, it must be magnetic. Magnetic nuclei include: a. all
More information4) protons experience a net magnetic field strength that is smaller than the applied magnetic field.
1) Which of the following CANNOT be probed by an spectrometer? See sect 16.1 Chapter 16: 1 A) nucleus with odd number of protons & odd number of neutrons B) nucleus with odd number of protons &even number
More information4) protons experience a net magnetic field strength that is smaller than the applied magnetic field.
1) Which of the following CANNOT be probed by an NMR spectrometer? See sect 15.1 Chapter 15: 1 A) nucleus with odd number of protons & odd number of neutrons B) nucleus with odd number of protons &even
More informationStructure Determination: Nuclear Magnetic Resonance Spectroscopy
Structure Determination: Nuclear Magnetic Resonance Spectroscopy Why This Chapter? NMR is the most valuable spectroscopic technique used for structure determination More advanced NMR techniques are used
More information16.1 Introduction to NMR. Spectroscopy
16.1 Introduction to NMR What is spectroscopy? Spectroscopy NUCLEAR MAGNETIC RESNANCE (NMR) spectroscopy may be the most powerful method of gaining structural information about organic compounds. NMR involves
More informationModule 13: Chemical Shift and Its Measurement
Subject Chemistry Paper No and Title Module No and Title Module Tag Paper 12: Organic Spectroscopy CHE_P12_M13_e-Text TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. Shielding and deshielding
More informationChapter 9. Nuclear Magnetic Resonance. Ch. 9-1
Chapter 9 Nuclear Magnetic Resonance Ch. 9-1 1. Introduction Classic methods for organic structure determination Boiling point Refractive index Solubility tests Functional group tests Derivative preparation
More informationNuclear Magnetic Resonance H-NMR Part 1 Introduction to NMR, Instrumentation, Sample Prep, Chemical Shift. Dr. Sapna Gupta
Nuclear Magnetic Resonance H-NMR Part 1 Introduction to NMR, Instrumentation, Sample Prep, Chemical Shift Dr. Sapna Gupta Introduction NMR is the most powerful tool available for organic structure determination.
More informationNuclear spin and the splitting of energy levels in a magnetic field
Nuclear spin and the splitting of energy levels in a magnetic field Top 3 list for 13 C NMR Interpretation 1. Symmetry 2. Chemical Shifts 3. Multiplicity 13 C NMR of C 3 O 1 NMR of C 3 O 13 C NMR of C
More informationNuclear Magnetic Resonance (NMR) Spectroscopy Introduction:
Nuclear Magnetic Resonance (NMR) Spectroscopy Introduction: Nuclear magnetic resonance spectroscopy (NMR) is the most powerful tool available for organic structure determination. Like IR spectroscopy,
More informationORGANIC - BROWN 8E CH NUCLEAR MAGNETIC RESONANCE.
!! www.clutchprep.com CONCEPT: 1 H NUCLEAR MAGNETIC RESONANCE- GENERAL FEATURES 1 H (Proton) NMR is a powerful instrumental method that identifies protons in slightly different electronic environments
More informationChapter 14 Spectroscopy
hapter 14 Spectroscopy There are four major analytical techniques used for identifying the structure of organic molecules 1. Nuclear Magnetic Resonance or NMR is the single most important technique for
More information- 1/2. = kb o = hνν + 1/2. B o increasing magnetic field strength. degenerate at B o = 0
NMR EXPERIMENT When magnetically active nuclei are placed into an external magnetic field, the magnetic fields align themselves with the external field into two orientations. During the experiment, electromagnetic
More informationNMRis the most valuable spectroscopic technique for organic chemists because it maps the carbon-hydrogen framework of a molecule.
Chapter 13: Nuclear magnetic resonance spectroscopy NMRis the most valuable spectroscopic technique for organic chemists because it maps the carbon-hydrogen framework of a molecule. 13.2 The nature of
More informationChapter 13 Structure t Determination: Nuclear Magnetic Resonance Spectroscopy
John E. McMurry www.cengage.com/chemistry/mcmurry Chapter 13 Structure t Determination: ti Nuclear Magnetic Resonance Spectroscopy Revisions by Dr. Daniel Holmes MSU Paul D. Adams University of Arkansas
More informationNUCLEAR MAGNETIC RESONANCE SPECTROSCOPY
NMR Spectroscopy 1 NULEAR MAGNETI RESONANE SPETROSOPY Involves interaction of materials with the low-energy radiowave region of the electromagnetic spectrum Origin of Spectra Theory All nuclei possess
More informationORGANIC - CLUTCH CH ANALYTICAL TECHNIQUES: IR, NMR, MASS SPECT
!! www.clutchprep.com CONCEPT: PURPOSE OF ANALYTICAL TECHNIQUES Classical Methods (Wet Chemistry): Chemists needed to run dozens of chemical reactions to determine the type of molecules in a compound.
More informationInstrumental Chemical Analysis
L15 Page1 Instrumental Chemical Analysis Nuclear Magnetic Resonance Dr. Ahmad Najjar Philadelphia University Faculty of Pharmacy Department of Pharmaceutical Sciences 1 st semester, 2017/2018 Nuclear Magnetic
More informationORGANIC - CLUTCH CH ANALYTICAL TECHNIQUES: IR, NMR, MASS SPECT
!! www.clutchprep.com CONCEPT: PURPOSE OF ANALYTICAL TECHNIQUES Classical Methods (Wet Chemistry): Chemists needed to run dozens of chemical reactions to determine the type of molecules in a compound.
More informationWilliam H. Brown & Christopher S. Foote
Requests for permission to make copies of any part of the work should be mailed to:permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 William H. Brown
More informationPrinciples of Molecular Spectroscopy: Electromagnetic Radiation and Molecular structure. Nuclear Magnetic Resonance (NMR)
Principles of Molecular Spectroscopy: Electromagnetic Radiation and Molecular structure Nuclear Magnetic Resonance (NMR) !E = h" Electromagnetic radiation is absorbed when the energy of photon corresponds
More informationExperiment 2 - NMR Spectroscopy
Experiment 2 - NMR Spectroscopy OBJECTIVE to understand the important role of nuclear magnetic resonance spectroscopy in the study of the structures of organic compounds to develop an understanding of
More informationTuesday, January 13, NMR Spectroscopy
NMR Spectroscopy NMR Phenomenon Nuclear Magnetic Resonance µ A spinning charged particle generates a magnetic field. A nucleus with a spin angular momentum will generate a magnetic moment (μ). If these
More informationChapter 13: Molecular Spectroscopy
Chapter 13: Molecular Spectroscopy Electromagnetic Radiation E = hν h = Planck s Constant (6.63 x 10-34 J. s) ν = frequency (s -1 ) c = νλ λ = wavelength (nm) Energy is proportional to frequency Spectrum
More informationIn a solution, there are thousands of atoms generating magnetic fields, all in random directions.
Nuclear Magnetic Resonance Spectroscopy: Purpose: onnectivity, Map of - framework Process: In nuclear magnetic resonance spectroscopy, we are studying nuclei. onsider this circle to represent a nucleus
More informationExperiment 11: NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY
Experiment 11: NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY Purpose: This is an exercise to introduce the use of nuclear magnetic resonance spectroscopy, in conjunction with infrared spectroscopy, to determine
More informationORGANIC - EGE 5E CH NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY
!! www.clutchprep.com CONCEPT: PURPOSE OF ANALYTICAL TECHNIQUES Classical Methods (Wet Chemistry): Chemists needed to run dozens of chemical reactions to determine the type of molecules in a compound.
More informationProton NMR. Four Questions
Proton NMR Four Questions How many signals? Equivalence Where on spectrum? Chemical Shift How big? Integration Shape? Splitting (coupling) 1 Proton NMR Shifts Basic Correlation Chart How many 1 H signals?
More informationNuclear Magnetic Resonance Spectroscopy (NMR)
OCR Chemistry A 432 Spectroscopy (NMR) What is it? An instrumental method that gives very detailed structural information about molecules. It can tell us - how many of certain types of atom a molecule
More informationChapter 13: Nuclear Magnetic Resonance (NMR) Spectroscopy direct observation of the H s and C s of a molecules
hapter 13: Nuclear Magnetic Resonance (NMR) Spectroscopy direct observation of the s and s of a molecules Nuclei are positively charged and spin on an axis; they create a tiny magnetic field + + Not all
More informationSpectroscopy in Organic Chemistry. Types of Spectroscopy in Organic
Spectroscopy in Organic Chemistry Spectroscopy Spectrum dealing with light, or more specifically, radiation Scope to see Organic Spectroscopy therefore deals with examining how organic molecules interact
More informationNUCLEAR MAGNETIC RESONANCE AND INTRODUCTION TO MASS SPECTROMETRY
NUCLEAR MAGNETIC RESONANCE AND INTRODUCTION TO MASS SPECTROMETRY A STUDENT SHOULD BE ABLE TO: 1. Identify and explain the processes involved in proton ( 1 H) and carbon-13 ( 13 C) nuclear magnetic resonance
More informationC NMR Spectroscopy
13.14 13 C NMR Spectroscopy 1 H and 13 C NMR compared: both give us information about the number of chemically nonequivalent nuclei (nonequivalent hydrogens or nonequivalent carbons) both give us information
More information1. neopentyl benzene. 4 of 6
I. 1 H NMR spectroscopy A. Theory 1. The protons and neutrons in atomic nuclei spin, as does the nucleus itself 2. The circulation of nuclear charge can generate a nuclear magnetic moment, u, along the
More informationChapter 16 Nuclear Magnetic Resonance Spectroscopy
hapter 16 Nuclear Magnetic Resonance Spectroscopy The Spinning Proton A spinning proton generates a magnetic field, resembling that of a small bar magnet. An odd number of protons in the nucleus creates
More information3.15 Nuclear Magnetic Resonance Spectroscopy, NMR
3.15 Nuclear Magnetic Resonance Spectroscopy, NMR What is Nuclear Magnetic Resonance - NMR Developed by chemists and physicists together it works by the interaction of magnetic properties of certain nuclei
More informationNMR Nuclear Magnetic Resonance Spectroscopy p. 83. a hydrogen nucleus (a proton) has a charge, spread over the surface
NMR Nuclear Magnetic Resonance Spectroscopy p. 83 a hydrogen nucleus (a proton) has a charge, spread over the surface a spinning charge produces a magnetic moment (a vector = direction + magnitude) along
More informationJanuary 30, 2018 Chemistry 328N
Lecture 4 Some More nmr January 30, 2018 Tricks for solving unknowns Review. Empirical formula is lowest common denominator ratio of atomic composition From Homework: unknown has an empirical formula of
More informationNuclear Spin States. NMR Phenomenon. NMR Instrumentation. NMR Active Nuclei. Nuclear Magnetic Resonance
Nuclear Magnetic Resonance NMR Phenomenon µ A spinning charged particle generates a magnetic field. A nucleus with a spin angular momentum will generate a magnetic moment (!). E Nuclear Spin States aligned
More informationNuclear Magnetic Resonance Spectroscopy
13 Nuclear Magnetic Resonance Spectroscopy Solutions to In-Text Problems 13.1 (b) Apply Eq. 13.2b with = 360 MHz. chemical shift in Hz = δ = (4.40)(360) = 1584 Hz 13.2 (b) Follow the same procedure used
More informationQuímica Orgânica I. Nuclear Magnetic Resonance Spectroscopy (II) Ciências Farmacêuticas Bioquímica Química AFB QO I 2007/08 1 AFB QO I 2007/08 2
Química Orgânica I Ciências Farmacêuticas Bioquímica Química AFB QO I 2007/08 1 Nuclear Magnetic Resonance Spectroscopy (II) AFB QO I 2007/08 2 1 Adaptado de Organic Chemistry, 6th Edition; L.G. Wade,
More information4. NMR spectra. Interpreting NMR spectra. Low-resolution NMR spectra. There are two kinds: Low-resolution NMR spectra. High-resolution NMR spectra
1 Interpreting NMR spectra There are two kinds: Low-resolution NMR spectra High-resolution NMR spectra In both cases the horizontal scale is labelled in terms of chemical shift, δ, and increases from right
More informationTo Do s. Answer Keys are available in CHB204H
To Do s Read Chapters 2, 3 & 4. Complete the end-of-chapter problems, 2-1, 2-2, 2-3 and 2-4 Complete the end-of-chapter problems, 3-1, 3-3, 3-4, 3-6 and 3-7 Complete the end-of-chapter problems, 4-1, 4-2,
More informationOAT Organic Chemistry - Problem Drill 19: NMR Spectroscopy and Mass Spectrometry
OAT Organic Chemistry - Problem Drill 19: NMR Spectroscopy and Mass Spectrometry Question No. 1 of 10 Question 1. Which statement concerning NMR spectroscopy is incorrect? Question #01 (A) Only nuclei
More informationTo Do s. Answer Keys are available in CHB204H
To Do s Read Chapters 2, 3 & 4. Complete the end-of-chapter problems, 2-1, 2-2, 2-3 and 2-4 Complete the end-of-chapter problems, 3-1, 3-3, 3-4, 3-6 and 3-7 Complete the end-of-chapter problems, 4-1, 4-2,
More informationIn a solution, there are thousands of atoms generating magnetic fields, all in random directions.
Nuclear Magnetic Resonance Spectroscopy: Purpose: onnectivity, Map of - framework Process: In nuclear magnetic resonance spectroscopy, we are studying nuclei. onsider this circle to represent a nucleus
More informationChapter 18: NMR Spectroscopy
The most important tool of the chemist for the determination of molecular structure is Nuclear Magnetic Resonance Spectroscopy, or NMR spectroscopy. NMR spectra are acquired on a special instrument called
More informationChapter 13 Nuclear Magnetic Resonance Spectroscopy
William. Brown Christopher S. Foote Brent L. Iverson Eric Anslyn http://academic.cengage.com/chemistry/brown Chapter 13 Nuclear Magnetic Resonance Spectroscopy William. Brown Beloit College Two Nobel Prizes
More informationChapter 13 Spectroscopy
hapter 13 Spectroscopy Infrared spectroscopy Ultraviolet-Visible spectroscopy Nuclear magnetic resonance spectroscopy Mass Spectrometry 13.1 Principles of Molecular Spectroscopy: Electromagnetic Radiation
More informationChem 325 NMR Intro. The Electromagnetic Spectrum. Physical properties, chemical properties, formulas Shedding real light on molecular structure:
Physical properties, chemical properties, formulas Shedding real light on molecular structure: Wavelength Frequency ν Wavelength λ Frequency ν Velocity c = 2.998 10 8 m s -1 The Electromagnetic Spectrum
More informationNuclear Magnetic Resonance Spectroscopy: Purpose: Connectivity, Map of C-H framework
Nuclear Magnetic Resonance Spectroscopy: Purpose: Connectivity, Map of C- framework Four Factors of Proton NMR (PMR OR NMR):. Symmetry: Number of chemically different protons (symmetry) as shown by number
More informationOther problems to work: 3-Chloropentane (diastereotopic H s), 1- chloropentane.
Let s look at some specific examples. Dichloroacetaldehyde, l 2 HHO, has two inequivalent toms, H1 and H2. We expect to see two resonances, one at around δ 10.5 ppm and one around δ 5.5 ppm. (The H2 resonance
More information7a. Structure Elucidation: IR and 13 C-NMR Spectroscopies (text , , 12.10)
2009, Department of Chemistry, The University of Western Ontario 7a.1 7a. Structure Elucidation: IR and 13 C-NMR Spectroscopies (text 11.1 11.5, 12.1 12.5, 12.10) A. Electromagnetic Radiation Energy is
More informationYale Chemistry 800 MHz Supercooled Magnet. Nuclear Magnetic Resonance
Yale Chemistry 800 Mz Supercooled Magnet Nuclear Magnetic Resonance B o Atomic nuclei in The absence of a magnetic field Atomic nuclei in the presence of a magnetic field α spin - with the field β spin
More informationCHEMISTRY Organic Chemistry Laboratory II Spring 2019 Lab #5: NMR Spectroscopy
Team Members: Unknown # CHEMISTRY 244 - Organic Chemistry Laboratory II Spring 2019 Lab #5: NMR Spectroscopy Purpose: You will learn how to predict the NMR data for organic molecules, organize this data
More informationObjective 4. Determine (characterize) the structure of a compound using IR, NMR, MS.
Objective 4. Determine (characterize) the structure of a compound using IR, NMR, MS. Skills: Draw structure IR: match bond type to IR peak NMR: ID number of non-equivalent H s, relate peak splitting to
More informationNuclear Magnetic Resonance Spectroscopy
Chapter 5 Nuclear Magnetic Resonance Spectroscopy http://www.yteach.co.uk/page.php/resources/view_all?id=nuclear_magnetic _resonance_nmr_spectroscopy_spin_spectrometer_spectrum_proton_t_pag e_5&from=search
More informationLecture 2 nmr Spectroscopy
Lecture 2 nmr Spectroscopy Pages 427 430 and Chapter 13 Molecular Spectroscopy Molecular spectroscopy: the study of the frequencies of electromagnetic radiation that are absorbed or emitted by substances
More informationOrganic Chemistry 321 Workshop: Spectroscopy NMR-IR Problem Set
Organic Chemistry 321 Workshop: Spectroscopy NMR-IR Problem Set 1. Draw an NMR spectrum for each of the following compounds. Indicate each peak by a single vertical line (for example, a quartet would be
More informationMagnetic Nuclei other than 1 H
Magnetic Nuclei other than 1 H 2 H (Deuterium): I = 1 H,D-Exchange might be used to simplify 1 H-NMR spectra since H-D couplings are generally small; - - - -O- - - -D 2 -O- triplet of triplets slightly
More information1. Predict the structure of the molecules given by the following spectral data: a Mass spectrum:m + = 116
Additional Problems for practice.. Predict the structure of the molecules given by the following spectral data: a Mass spectrum:m + = IR: weak absorption at 9 cm - medium absorption at cm - NMR 7 3 3 C
More informationSECOND YEAR ORGANIC CHEMISTRY - REVISION COURSE Lecture 2 MOLECULAR STRUCTURE 2: SPECTROSCOPIC ANALYSIS
Prof Ben Davis SECOND YEAR ORGANIC CEMISTRY - REVISION COURSE Lecture 2 MOLECULAR STRUCTURE 2: SPECTROSCOPIC ANALYSIS Books: Williams and Fleming, " Spectroscopic Methods in Organic Chemistry", arwood
More informationNMR Spectroscopy. for 1 st B.Tech INTRODUCTION Lecture -1 Indian Institute of Technology, Dhanbad
NMR Spectroscopy for 1 st B.Tech Lecture -1 Indian Institute of Technology, Dhanbad by Dr. R P John & Dr. C. Halder INTRODUCTION Nucleus of any atom has protons and neutrons Both Proton and Neutron has
More informationHWeb27 ( ; )
HWeb27 (9.1-9.2; 9.12-9.18) 28.1. Which of the following cannot be determined about a compound by mass spectrometry? [a]. boiling point [b]. molecular formula [c]. presence of heavy isotopes (e.g., 2 H,
More information1,1,2-Tribromoethane. Spin-Spin Coupling
NMR Spin oupling Spin-Spin oupling Spectra usually much more complicated than a series of single lines, one for each type of hydrogen. Peaks are often split into a number of smaller peaks, sometimes with
More informationUsing NMR and IR Spectroscopy to Determine Structures Dr. Carl Hoeger, UCSD
Using NMR and IR Spectroscopy to Determine Structures Dr. Carl Hoeger, UCSD The following guidelines should be helpful in assigning a structure from NMR (both PMR and CMR) and IR data. At the end of this
More informationNuclear Magnetic Resonance Spectroscopy Thomas Wenzel Department of Chemistry Bates College, Lewiston ME
Nuclear Magnetic Resonance Spectroscopy Thomas Wenzel Department of Chemistry Bates College, Lewiston ME 04240 twenzel@bates.edu The following textual material is designed to accompany a series of in-class
More informationAnalysis of NMR Spectra Part 2
Analysis of NMR Spectra Part 2-1- Analysis of NMR Spectra Part 2 "Things should be made as simple as possible, but not any simpler." Albert Einstein 1.1 Review of Basic NMR Concepts NMR analysis is a complex
More information11. Proton NMR (text , 12.11, 12.12)
2009, Department of Chemistry, The University of Western Ontario 11.1 11. Proton NMR (text 12.6 12.9, 12.11, 12.12) A. Proton Signals Like 13 C, 1 H atoms have spins of ±½, and when they are placed in
More informationCHEM 322 Laboratory Methods in Organic Chemistry. Introduction to NMR Spectroscopy
EM 322 Laboratory Methods in Organic hemistry Introduction to NMR Spectroscopy What structural information does NMR spectroscopy provide? 1) hemical shift (δ) data reveals the molecular (functional group)
More informationLecture Notes Chem 51A S. King
Lecture Notes hem 51A S. King hapter 14 Nuclear Magnetic Resonance Spectroscopy Nuclear Magnetic Resonance (NMR) spectroscopy uses energy in the radiowave portion of the electromagnetic spectrum. The nuclei
More informationThe resonance frequency of the H b protons is dependent upon the orientation of the H a protons with respect to the external magnetic field:
Spin-Spin Splitting in Alkanes The signal arising from a proton or set of protons is split into (N+1) lines by the presence of N adjacent nuclei Example 1: Bromoethane The resonance frequency of the H
More informationSpectroscopy. Empirical Formula: Chemical Formula: Index of Hydrogen Deficiency (IHD)
Spectroscopy Empirical Formula: Chemical Formula: Index of Hydrogen Deficiency (IHD) A)From a structure: B)From a molecular formula, C c H h N n O o X x, Formula for saturated hydrocarbons: Subtract the
More informationCHEM311 FALL 2005 Practice Exam #3
EM311 FALL 2005 Practice Exam #3 Instructions: This is a multiple choice / short answer practice exam. For the multiple-choice questions, there may be more than one correct answer. If so, then circle as
More informationNuclear Magnetic Resonance Spectroscopy
Nuclear Magnetic Resonance Spectroscopy Features: Used to identify products of reactions Also gives information about chemical environment, connectivity and bonding of nuclei Requirements: Pure or mostly
More informationWith that first concept in mind, it is seen that a spinning nucleus creates a magnetic field, like a bar magnet
NMR SPECTROSCOPY This section will discuss the basics of NMR (nuclear magnetic resonance) spectroscopy. Most of the section will discuss mainly 1H or proton spectroscopy but the most popular nuclei in
More informationIntroduction to NMR spectroscopy
Introduction to NMR spectroscopy Nuclei of isotopes which possess an odd number of protons, an odd number of neutrons, or both, have a nuclear spin quantum number, I, such that, I = 1/2n, where n is an
More informationChem 213 Final 2012 Detailed Solution Key for Structures A H
Chem 213 Final 2012 Detailed Solution Key for Structures A H COMPOUND A on Exam Version A (B on Exam Version B) C 8 H 6 Cl 2 O 2 DBE = 5 (aromatic + 1) IR: 1808 cm 1 suggests an acid chloride since we
More informationTo Do s. Read Chapter 3. Complete the end-of-chapter problems, 3-1, 3-3, 3-4, 3-6 and 3-7. Answer Keys are available in CHB204H
Read Chapter 3. To Do s Complete the end-of-chapter problems, 3-1, 3-3, 3-4, 3-6 and 3-7 Answer Keys are available in CB204 NMR Chemical Shifts Further Discussion A set of spectral data is reported when
More informationAnswers to Assignment #5
Answers to Assignment #5 A. 9 8 l 2 5 DBE (benzene + 1 DBE) ( 9 2(9)+2-9 8+1+1 = 10 ˆ 5 DBE) nmr pattern of two doublets of equal integration at δ7.4 and 7.9 ppm means the group (the δ7.9 shift) IR band
More information1 H NMR Spectroscopy: Background
1 NMR Spectroscopy: Background Molecules are too small to be observed with the naked eye. In fact, it was only recently that the technology was developed to directly observe molecules by a specialized
More informationDepartment of Chemistry SUNY/Oneonta. Chem Organic Chemistry I
Department of Chemistry SUNY/Oneonta Chem 221 - Organic Chemistry I Examination #4 - ANSWERS - December 11, 2000 Answer to question #32 corrected 12/13/00, 8:30pm. INSTRUCTIONS This examination is in multiple
More informationMOLECULAR SPECTROSCOPY AND PHOTOCHEMISTRY
20 CHAPTER MOLECULAR SPECTROSCOPY AND PHOTOCHEMISTRY 20.1 Introduction to Molecular Spectroscopy 20.2 Experimental Methods in Molecular Spectroscopy 20.3 Rotational and Vibrational Spectroscopy 20.4 Nuclear
More informationChapter 16 Nuclear Magnetic Resonance Spectroscopy
Chapter 16 Nuclear Magnetic Resonance Spectroscopy Review of Concepts Fill in the blanks below. To verify that your answers are correct, look in your textbook at the end of Chapter 16. Each of the sentences
More informationNuclear Magnetic Resonance
Nuclear Magnetic Resonance PRINCIPLES OF NMR SPECTROSCOPY Contents Principles of nuclear magnetic resonance The nmr spectrometer Basic principles in nmr application NMR tools used to obtain information
More informationNMR spectra of some simple molecules. Effect of spinning: averaging field inhomogeneity (nmr1.pdf pg 2)
NMR spectra of some simple molecules Effect of spinning: averaging field inhomogeneity (nmr1.pdf pg 2) N S H 0 H o Because the protons have a magnetic field associated with them, the field changes as across
More information13.24: Mass Spectrometry: molecular weight of the sample
hapter 13: Spectroscopy Methods of structure determination Nuclear Magnetic Resonances (NMR) Spectroscopy (Sections 13.3-13.19) Infrared (IR) Spectroscopy (Sections 13.20-13.22) Ultraviolet-visible (UV-Vis)
More information(Refer Slide Time: 1:03)
Principles and Applications of NMR spectroscopy Professor Hanudatta S. Atreya NMR Research Centre Indian Institute of Science Bangalore Module 1 Lecture No 05 Welcome back! In the last class we looked
More informationCH Exam #4 (Take Home) Date Due: 11/25,26/2013
CH2710 - Exam #4 (Take Home) Date Due: 11/25,26/2013 Section I - Multiple Choice - Choose the BEST answer from the choices given and place the letter of you choice in the space provided. 1. Energy absorbed
More informationBasic Concepts of NMR: Identification of the Isomers of C 4 O 2. by 1 H NMR Spectroscopy
Basic Concepts of NM: Identification of the Isomers of C H 8 O by H NM Spectroscopy Objectives NM spectroscopy is a powerful tool in determining the structure of compounds. Not only is it able to give
More information