NMR spectroscopy in the undergraduate curriculum

176 Pages·2013·3.395 MB·English

by  Anna, Laura J., Soulsby, David, Wallner, Anton S

1 NMR Spectroscopy in the
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Soulsby et al.; NMR Spectroscopy in the Undergraduate Curriculum: First Year and Organic Chemistry Courses Volume 2
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
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Soulsby et al.; NMR Spectroscopy in the Undergraduate Curriculum: First Year and Organic Chemistry Courses Volume 2
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
1221
ACS SYMPOSIUM SERIES
NMR Spectroscopy in the
Undergraduate Curriculum:
First Year and Organic
Chemistry Courses
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21/ David Soulsby, Editor
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0. UniversityofRedlands, Redlands, California
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6 | Laura J. Anna, Editor
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AmericanChemicalSociety,Washington,DC
DistributedinprintbyOxfordUniversityPress
Soulsby et al.; NMR Spectroscopy in the Undergraduate Curriculum: First Year and Organic Chemistry Courses Volume 2
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
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NMRspectroscopyintheundergraduatecurriculum:firstyearandorganic
chemistrycoursesVolume2/DavidSoulsby,editor,
UniversityofRedlands,Redlands,California,LauraJ.Anna,editor,MontgomeryCollege
1 Rockville,Maryland,AntonS.Wallner,editor,BarryUniversity,MiamiShores,Florida;
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0 sponsoredbytheACSDivisionofChemicalEducation.
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1.f pagescm.-- (ACSsymposiumseries;1221)
22 Includesbibliographicalreferencesandindex.
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6- ISBN978-0-8412-3138-2(print)--ISBN978-0-8412-3137-5(ebook)
01 1. Nuclearmagneticresonancespectroscopy.2. Chemistry,Physicalandtheoretical--
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k- Studyandteaching. I.Soulsby,David,1974-editorofcompilation.II.Anna,LauraJ.,
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1/ editorofcompilation.III.Wallner,AntonS.,editorofcompilation.
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0 QD96.N8N5882013
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Soulsby et al.; NMR Spectroscopy in the Undergraduate Curriculum: First Year and Organic Chemistry Courses Volume 2
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
Foreword
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mechanism for publishing symposia quickly in book form. The purpose of
the series is to publish timely, comprehensive books developed from the ACS
sponsoredsymposiabasedoncurrentscientificresearch. Occasionally,booksare
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Soulsby et al.; NMR Spectroscopy in the Undergraduate Curriculum: First Year and Organic Chemistry Courses Volume 2
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
Preface
ThesecondvolumeofNMRSpectroscopyintheUndergraduateCurriculum
continues the work we started with the first volume in providing effective
approachesforusingnuclearmagneticresonancespectrometersaspowerfultools
for investigating a wide variety of phenomena at the undergraduate level. This
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0 volumefocusesonfirstyearandorganicchemistrycourses. Ourhopeisthatthe
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1.pr applications and strategies in this volume are helpful to those who are looking
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2 to transform their curriculum by integrating more NMR spectroscopy, to those
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16- who might not have considered NMR spectroscopy as a tool for solving certain
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k-2 types of problems, or for those seeking funding for a new or replacement NMR
1/b spectrometer. As with the previous volume, this volume includes contributions
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0 fromauthorswhohavepresentedatoneormoreofourNMRSpectroscopyinthe
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10. UndergraduateCurriculumsymposiathathavebeenheldannuallysince2009at
oi: theAmericanChemicalSociety(ACS)SpringNationalMeetings.
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6 | We are extremely grateful to everybody who worked tirelessly to bring this
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20 projecttofruition. Wethankourauthors,becausewithouttheircontributionsand
15, passion for sharing their innovative methods for integrating NMR spectroscopy
ber intotheundergraduatecurriculum,thisvolumewouldnotexist. Allofourauthors
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e thoughtfullyrespondedtoeditorialandpeer-reviewercomments,andforthatwe
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Se thank them. We also thank our many colleagues who acted as peer-reviewers
b): for this volume. They selflessly dedicated significant amounts of their valuable
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time to providing constructive criticism to all of our authors. Their work made
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at everybody’sworkstrongerasaresult. AtACSBooks,wethankBobHauserman,
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n TimMarney,ArleneFurman,AnneBrenner,andtheentirestaffwhosetechnical
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ati expertise, rapid responses to our many questions, and understanding when we
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bli made mistakes made this entire endeavor possible. Finally, we acknowledge
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Fisher who have kindly provided sponsorship for our NMR Spectroscopy in the
Undergraduate Curriculum symposium over the past seven years. (DS, LJA,
ASW).
DavidSoulsby
ChemistryDepartment,UniversityofRedlands
1200E.ColtonAve.
Redlands,California92373
United States
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Soulsby et al.; NMR Spectroscopy in the Undergraduate Curriculum: First Year and Organic Chemistry Courses Volume 2
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
LauraJ.Anna
ChemistryDepartment,MontgomeryCollege
51MannakeeStreet
Rockville,Maryland20850
United States
AntonS.Wallner
CollegeofArtsandSciences,BarryUniversity
11300NE2ndAve.
MiamiShores,Florida33161
United States
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Soulsby et al.; NMR Spectroscopy in the Undergraduate Curriculum: First Year and Organic Chemistry Courses Volume 2
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
Chapter 1
Introduction to NMR Spectroscopy in
the Undergraduate Curriculum
DavidSoulsby*,1andAntonS.Wallner*,2
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h 1ChemistryDepartment,UniversityofRedlands,1200E.ColtonAve.,
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6-1 2CollegeofArtsandSciences,BarryUniversity,11300NE2ndAve.,
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2 [email protected](A.S.Wallner).
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1 NMR spectroscopy is a powerful tool that is used in many
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Thepossibilityofthegenerationofasignalfromnucleiwithspinperturbed
by a magnetic field was first proposed in 1936 by Gorter (1–3). His attempts
to observe signals for 7Li (in LiF crystals) and 1H (in potassium alum) were
unsuccessful due to long relaxation times of the crystalline samples. In 1946,
Bloch, HansonandPackard(4)andPurcell, Torrey, andPound(5)observedthe
firstnuclearmagneticresonance(NMR)signalsinwaterandparaffinrespectively.
Fromthesebeginnings,NMRhasexpandedgreatlyoverthepast70years.
Early NMR technology used continuous wave methodology and permanent
ironmagnets. Theseinstrumentscouldeasilydetect1Hresonancesandprovided
useful structural information for a variety of compounds. In 1966, Ernst and
Andersen reported the use of a new Fourier Transform (FT) technique that
©2016AmericanChemicalSociety
Soulsby et al.; NMR Spectroscopy in the Undergraduate Curriculum: First Year and Organic Chemistry Courses Volume 2
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
improved sensitivity by a factor of ten or shortened the time for acquisition (for
the same sensitivity) by a factor of 100 compared to the conventional sweep
scan method (6). Around this same period, researchers were developing stable,
usefulsuperconductingmaterials(niobium-tinandniobium-titaniumalloys)that
could be used to create large magnetic fields at liquid helium, superconducting
temperatures. Thesefieldswereoften10timesgreaterthanthefieldachievedby
permanentironmagnets;theyproducedmagneticfieldswithgreaterhomogeneity,
andweresmallerindesign(7,8).
The use of both superconducting magnet materials and FT-NMR produced
a variety of new techniques and research projects in the area of NMR
during the next several decades. Multi-nuclear NMR (most notably 13C),
multi-dimensionalNMR,andnovelpulsesequencesintheseareasalldeveloped
1 during this period (see Volume 1 of this series for a review) (9). Additionally,
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6-1 commonplace during the 1970’s and 1980’s. This expanded the application
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bk- applications for non-invasive, non-destructive evaluation. Many of these
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6 | d knowledge for a well-trained scientist or clinician. Most notably, the American
1 Chemical Society (ACS) Committee on Professional Training lists NMR
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er and a necessary instrumentation experience for trained undergraduate students
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We manyyearstheNationalScienceFoundation(NSF)supportedtheacquisitionof
e ( bothpermanentandsuperconductingNMRinstrumentsthroughitsnowobsolete
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permanent magnet NMR instruments through these programs. Unfortunately,
the only current general program available is the highly competitive Major
Research Instrumentation (MRI) program which has a focus on research rather
thancurricularneeds. Issuesassociatedwithfundingandmaintenancecostshave
led to a resurgence in the use of cheaper, permanent magnet NMR instruments
forcurricularuse.
In 1995, Anasazi Instruments, Incorporated developed a method to upgrade
existingpermanentmagnetstoFTcapabilitiesatareasonablecost. Thisupgrade
combined with current software for data processing provides for high quality,
well-resolved spectra without the cost and maintenance of a superconducting
magnet. A variety of other companies have since entered the market of table
top NMR (Magritek, Nanalysis Corporation, Oxford, Process NMR Associates
and Thermo Scientific). These instruments combined with software packages
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Soulsby et al.; NMR Spectroscopy in the Undergraduate Curriculum: First Year and Organic Chemistry Courses Volume 2
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
including, MestReLab, ACORN, ACD Labs, Bruker TopSpin, Cambridge Soft
– ChemDraw, Science Soft NMRanalyst, Nucleomatica iNMR, and ModGraph
NMRPredict, allow for collection and analysis of high quality spectra for
classroom and research use. Also, database collections are growing where the
NMR and scientific community can post and store NMR spectra of compounds
they have collected in their labs. Most notably, ChemSpider is a dynamic,
growingrepositoryofNMRspectra(15).
Unlike most other instrumental methods, modern NMR spectroscopy
continuestoinnovateatafundamentallevel. ArangeofroutinetoadvancedNMR
experimentsareavailableonmanyNMRspectrometers,withnewpulsesequences
published frequently. These NMR experiments allow for the acquisition of data
that can reveal a range of connectivities. As part of this introductory chapter
1 and as a guide to both the novice and more advanced NMR user, we provide an
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6 | d spectrum is often one of the first spectra acquired (16). The 1D 1H NMR pulse
01 sequence is found on all modern NMR spectrometers, though there are some
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5, interestingvariationsthatwillbeintroducedlater. A1HNMRspectrumprovides
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We that signal overlap can occur, particularly in complex molecules or mixtures.
e ( Withlowmagneticfieldstrengthinstruments,analysiscanbefurthercomplicated
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blic (i.e., ΔJ≈Δυ or ΔJ>Δυ). First-order spectra, which are more straightforward to
u analyze, occur when ΔJ<<Δυ, and are more common at higher magnetic field
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strengths.
The 13C NMR experiment, which is nearly always run as a 1H-decoupled
experiment, provides a spectrum where each chemically non-equivalent carbon
atomappearsasasinglet(17,18). 13Cnucleicoveramuchlargerspectralwidth
(0-220 ppm), and the larger chemical shift scale means that signal overlap is
rare. Furthermore, by decoupling protons during acquisition, non-quaternary
carbonsignalsareenhancedbyupto200%duetothenuclearOverhausereffect
(NOE)(19). Muchlikethe1HNMRexperiment,chemicalshiftpositionprovides
information about functional groups, and signal height, can in some cases,
provide information about chemical shift equivalency or symmetry. However,
the NOE effect and the long relaxation delays of 13C atoms mean that these
spectra cannot be accurately quantitated. However, quantification is possible
using approaches that ‘gate’ the broadband decoupler (20) in combination with
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Soulsby et al.; NMR Spectroscopy in the Undergraduate Curriculum: First Year and Organic Chemistry Courses Volume 2
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.