Post on 04-Apr-2018
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Hardware y Software
Crio-Magneto superconductor
Sonda superconductora RMN
Consola de Radiofrecuencia
Computadora + Software RMN
+ Impresora/Plotter
Solucin RMN
Preparacin de la muestra
Presentacin de los datos
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CRIOMAGNETOS SUPERCONDUCTORES
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alambre superconductor
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SEGURIDAD CON LOS MAGNETOS DE RMN
Los magnetos de RMN siempre estn cargados!
Los magnetos de RMN pueden interferir con dispositivos
mdicos (p. ej. marcapasos, implantes metlicos)
Los magnetos de RMN y las consolas de RF pueden interferir
con dispositivos electrnicos y mecnicos y pueden daarlos
(telfonos celulares, buscadores, relojes, llaves de autos, etc.)
Los magnetos de RMN borrarn tarjetas de crdito,, tarjetas
de identificacin, discos de 31/2, discos duros, USBs (I-pods,
mp3).
Atraen objetos ferromagnticos de cualquier tamao p. ej.
clips, monedas, llaves, ploumas, tijeras, tornillos, sillasmetlicas, cilindros de gas, etc.) y el espectrmetro y la gente
pueden sufrir graves daos o lesiones, si se manejan sin
cuidado.
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Los magnetos de RMN contener criognicos (helio y nitrgeno
lquido)
Los criognicos pueden causar quemaduras graves si no semaneja adecuadamente (use proteccin para los ojos y guantes).
Crigenos se evaporan y pueden causar asfixia si no est bien
ventilado el laboratorio.
Cuando se apaga un imn se vaporizan hasta 100 litros de heliolquido en cuestin de minutos (2600 pies cbicos, 70,000 litros de
gas) y puede causar asfixia, incluso si el laboratorio est bien
ventilado. Si un imn se apaga, salga del laboratorio
inmediatamente. No entre en pnico, el gas helio se elevar hasta
el techo. Durante una recarga, la tubera se puede romper. Los tubos
congelados de plstico se rompen como un cristal!
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CONSOLA CON COMPUTADORADE RMN
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GENERADOR DE LA SEAL DERADIOFRECUENCIA
Desacoplador (
1
H):Amplificador
Generador de Frecuencia
Transmisor: Amplificador
Generador de Frecuencia
Frequency Generators and Signal Amplifiers are required for each RF channel.Our spectrometers have 2 channels, modern spectrometers can have up to 8 channels.
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SONDAS DE RMN
Slidos
Lquidos
Slidos
Lquidos
Magic angle
(54.7)
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MUESTRAS PARA RMN
Types of NMR sample holders
Sample preparation
Spectrum quality
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TIPOS DE PORTADORES DEMUESTRA PARA RMN
Solid State
Sample Rotors
Solution NMR
Sample TubeSpinners
NMR SampleTubes with Caps
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PREPARACIN DE LA MUESTRA PARA RMNTubes and Caps:
NMR tubes are a standard length (7 and 9 inch). When chipped (and reducedin length) they should not be reused as an unbalanced tube will not spin.
Always clean the tubes thoroughly after use.First use the solvent you were using to recover your previous sample,then rinse several times with acetone and finally dry the sample tube layingflat on a layer of kimwipes or placed upside-down on a kimwipe in a beakeror Erlenmeyer flask. Choose the container so the tubes stand vertically.Dont heat the tubes above 50 C, as the glass might warp.Always store unused, clean tubes uncapped and laying on a flat surface.
Tube caps are disposable and replacements can be easily obtained in bagsof 100 ($5) or 1000 ($40 at www.wilmad.com).
Degassing Samples:
NMR spectra recorded using degassed solvents usually benefit fromreduced half-height line-width and thus better S/N. (O2 gas is paramagnetic!)
There are several ways of degassing your sample: the best is the freeze-pump-thaw technique, placing the sample in a ultrasonic bath works moderately well, bubbling nitrogen through or over the sample less well.
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Quantity:
For proton NMR spectra of small organic compounds (up to MW=500)anything between 1 and 20 mg of sample will be fine.Concentrated solutions can be viscous and may result in broad signals.Very dilute samples could be masked by impurities and solvent peaks.
Carbon-13 is present at approximately 1.1 % natural abundance.It is intrinsically less sensitive than protons (approx. six thousand times).Please provide as much sample as possible, 50 - 100 mg (or more) is fine.
Preparing two samples - one dilute sample for proton NMR and oneconcentrated sample for carbon NMR is a useful, but unnecessary practice.
Solvent height (volume) should be uniform, 5 cm or 2 inches equal 0.5 ml.The ends of the sample distort the field homogeneity, shimming on eachsample corrects this effect and takes just a minute or so. However, vastlydifferent solvent heights (volumes) prevent complete correction andrequire many minutes shimming to achieve acceptable homogeneity.
Samples prepared with too much solvent waste both time and money, andprovide poorer S/N. However, If you have limited amounts of sample (lessthan 1 mg), using less solvent is permissible.Minimum height: 1 cm, however, this requires special positioning of thesample tube and very intensive shimming.
PREPARACIN DE LA MUESTRA PARA RMN
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Use clean + dry NMR tubes and caps
(tubes can be re-used, caps should not!)
0.5 ml deuterated solvent
(i.e. CDCl ,C D , acetone-d ,etc.)
substrate requirements for routine spectra:
10 mg for proton NMR
100 mg for carbon-13 NMR
min. filling height of tube: 2 inches (5 cm)
Cleaning of tubes:1. rinse with solvent you were using
2. rinse with acetone
3. dry in (vacuum-)oven at low temperature
3 6 6 6
5 mm
PREPARACIN DE LA MUESTRA PARA RMN
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Clean
clear
solution
Suspension
or opaque
solution
PrecipitateNot
enough
solvent
Two
phases
Concentration
gradient
GOOD! B a d S a m p l e s !
PREPARACIN DE LA MUESTRA PARA RMN
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Shimming
improves the
magnetic field
homogeneity
If the magnetic field is not uniform within the sample, molecules in
different positions will experience different field strengths.
This will produce broad, distorted, or additional signals.
PREPARACIN DE LA MUESTRA PARA RMN
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are the result of:
Homogeneity of magnetic fieldSample preparation
Choice of solvent
Data acquisition parameters
Processing procedures
Espectros correctos e
incorrectos en RMN
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ppm
ppm
Espectro correcto!!
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Integrales
Peakpicking
ppm scale ppm
ppm
Espectro incorrecto?
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20ppm
ppm
Espectro correcto!!
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Espectro incorrecto?
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Signal/Noise
ratio bad
No units specified for
axis and peak picking
Espectro incorrecto!!
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Espectro incorrecto?
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Tall signals
are cut off
Espectro incorrecto!!
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Espectro incorrecto?
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Signals too small
(only allowed when trying to
compare signal intensities between
different spectra)
Espectro incorrecto!!
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Espectro incorrecto?
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Broad signals Possible reasons:poor shimming
viscous sample
sample too concentrated
suspended particles in sample
excessive line broadening may
have been used during processing
Espectro incorrecto!!
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Espectro incorrecto?
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Signals are distorted(automatic phase correction
is often insufficient)
Excessive peak picking
(low p.p. threshold,
also due to improper phasing)
Espectro incorrecto!!
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Espectro incorrecto?
Bad spectrum ?
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Bad spectrum ?
Areas without signals should be excluded.
(If you want to print all your spectra with adefault range, i.e. 0-10 ppm, dont forget to
print detailed expansions.)
Espectro incorrecto?
Lab Assignments
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Lab Assignments
1. 2X2 hrs Comprehensive 1H NMR and Indirect 13C Observation X00 mg2. 3 hrs Pulse Width Calibration and B1 100 mg
3. 2X2 hrs Rare spin NMR concentrated (80-90%)4. 3 hrs Decoupling 1H from 13C and B2 100 mg5. 2 hrs Spin Echo and Spin/Spin Relaxation, T2 100 mg6. 2 hrs Spin/Lattice Relaxation, T1 100 mg7. 3 hrs Nuclear Overhauser Effect 25 mg
8. 2 hrs Polarization Transfer and DEPT 100 mg9. 3 hrs 13C CP/MAS in Solids (sample provided)10. 2 hrs HETCOR (1H/13C COSY) 100 mg
11. 2 hrs 1H COSY / NOESY (optional) 25 mg
Use your own samples, if possible. Familiarize yourselves with the procedures
for each experiment, before you come to the lab. Print the manuals.
http://www.chem.binghamton.edu/NMR
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In all assignments you are expected to report on the following information:
Signal-to-noise ratio
Chemical shifts and method of reference in relation to structure
J coupling (homo and heteronuclear) in relation to structure Peak intensity and area in relation to concentration and structure/dynamics/relaxation
Effect of B0 / lab magnetic field strength, Larmor frequency and gyromagnetic ratio
Effect of B0 inhomogeneity
Pulse width and tip angle
Magnitude of B1 and B2 fields / rf field strengths used
Effect of B1 and B2 inhomogeneity
Effects of O1 and O2 / frequency offsets
Effects of sample spinning and location of spinning sidebands
Method of decoupling if used as well as effectiveness
Solvent and temperature used
Pulse sequence and instrument control programming
All critical instrument or data processing parameters
Vector and spin diagrams, as needed. Note any experimental or instrumental anomalies
The spectrometer manual to be used in this course can be downloaded from:http://www.chem.binghamton.edu/staff/schulte/CHEM585f/Chem585f-Bruker.doc
http://www.chem.binghamton.edu/staff/schulte/CHEM585f/Chem585f-Bruker.dochttp://www.chem.binghamton.edu/staff/schulte/CHEM585f/Chem585f-Bruker.dochttp://www.chem.binghamton.edu/staff/schulte/CHEM585f/Chem585f-Bruker.dochttp://www.chem.binghamton.edu/staff/schulte/CHEM585f/Chem585f-Bruker.doc