Spectroscopy nuclear magnetic resonance The nmr spectra included
- Slides: 54
Spectroscopy nuclear magnetic resonance
The nmr spectra included in this presentation have been taken from the SDBS database with permission. National Institute of Advanced Industrial Science and Technology (http: //www. aist. go. jp/RIODB/SDBS/menu-e. html)
Nuclear Magnetic Resonance (nmr) -the nuclei of some atoms spin: 1 H, 13 C, 19 F, … -the nuclei of many atoms do not spin: 2 H, 12 C, 16 O, … -moving charged particles generate a magnetic field ( ) -when placed between the poles of a powerful magnet, spinning nuclei will align with or against the applied field creating an energy difference. Using a fixed radio frequency, the magnetic field is changed until the ΔE = EEM. When the energies match, the nuclei can change spin states (resonate) and give off a magnetic signal. ΔE
magnetic field = 14, 092 gauss for 1 H v = 60, 000 Hz (60 MHz) nmr spectrum intensity magnetic field 10 9 8 7 6 5 4 3 chemical shift (ppm) 2 1 0
1 H nuclei are shielded by the magnetic field produced by the surrounding electrons. The higher the electron density around the nucleus, the higher the magnetic field required to cause resonance. CH 3 Cl lower electron density resonate at lower applied field CHCCl 3 ? ? versus CH 4 higher electron density resonate at higher applied field
Information from 1 H-nmr spectra: 1. Number of signals: How many different types of hydrogens in the molecule. 2. Position of signals (chemical shift): What types of hydrogens. 3. Relative areas under signals (integration): How many hydrogens of each type. 4. Splitting pattern: How many neighboring hydrogens.
1. Number of signals: How many different types of hydrogens in the molecule. 2. Magnetically equivalent hydrogens resonate at the same applied field. 3. Magnetically equivalent hydrogens are also chemically equivalent. 4. # of signals? CH 4 CH 3
number of signals?
2. Position of signals (chemical shift): what types of hydrogens. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. primary secondary tertiary 1. 5 aromatic allyl 1. 7 benzyl 2. 2 -3 chlorides bromides iodides 2 -4 alcohols 0. 9 ppm 1. 3 6 -8. 5 3 -4 2. 5 -4 H-C-I 3. 4 -4 1 -5. 5 H-C-Cl H-C-Br Note: combinations may greatly influence chemical shifts. For example, the benzyl hydrogens in benzyl chloride are shifted to lower field by the chlorine and resonate at 4. 5 ppm. H-C-O H-O- (variable)
reference compound = tetramethylsilane (CH 3)4 Si @ 0. 0 ppm magnetic field remember: chemical shift convention: let most upfield signal = a, next most upfield = b, etc. … c b a tms
toluene b a
chemical shifts
3. Integration (relative areas under each signal): how many hydrogens of each type. 4. a b c 5. CH 3 CH 2 Br 6. 7. 8. a b a 9. CH 3 CHCH 3 10. Cl a 3 H a: b: c=3: 2: 2 b c 2 H 2 H a b 6 H 1 H a: b=6: 1
integration
c b a Integration: measure the height of each “step” in the integration and then calculate the lowest whole number ratio: a: b: c = 24 mm : 16 mm : 32 mm = 1. 5 : 1. 0 : 2. 0 3 H : 2 H : 4 H
If the formula is known ( C 8 H 9 OF ), add up all of the “steps” and divide by the number of hydrogens = (24 + 16 + 32 mm) / 9 H = 8. 0 mm / Hydrogen. a = 24 mm / 8. 0 mm/H 3 H; b = 16 mm/8. 0 mm/H 2 H; c = 32 mm/8. 0 mm/H 4 H.
4. Splitting pattern: how many neighboring hydrogens. 5. In general, n-equivalent neighboring hydrogens will split a 1 H signal into an ( n + 1 ) Pascal pattern. 6. “neighboring” – no more than three bonds away 7. n 8. 0 singlet 1 9. 1 doublet 2 10. 2 triplet 3 11. 3 quartet 4 n+1 Pascal pattern: 1 1 1 2 3 1
note: n must be equivalent neighboring hydrogens to give rise to a Pascal splitting pattern. If the neighbors are not equivalent, then you will see a complex pattern (aka complex multiplet). note: the alcohol hydrogen –OH usually does not split neighboring hydrogen signals nor is it split. Normally a singlet of integration 1 between 1 – 5. 5 ppm (variable).
splitting pattern?
Information from 1 H-nmr spectra: 1. Number of signals: How many different types of hydrogens in the molecule. 2. Position of signals (chemical shift): What types of hydrogens. 3. Relative areas under signals (integration): How many hydrogens of each type. 4. Splitting pattern: How many neighboring hydrogens.
cyclohexane a singlet 12 H
2, 3 -dimethyl-2 -butene a singlet 12 H
benzene a singlet 6 H
p-xylene a b a a singlet 6 H b singlet 4 H
tert-butyl bromide a singlet 9 H
ethyl bromide a b CH 3 CH 2 -Br a triplet 3 H b quartet 2 H
1 -bromopropane a b c CH 3 CH 2 -Br a b c triplet 3 H complex 2 H triplet 3 H
isopropyl chloride a b a CH 3 CHCH 3 Cl a doublet 6 H b septet 1 H
2 -bromobutane b d c a CH 3 CHCH 2 CH 3 Br a b c d triplet doublet complex 3 H 3 H 2 H 1 H
o-methylbenzyl chloride
ethanol a c b CH 3 CH 2 -OH a triplet 3 H b singlet 1 H c quartet 2 H
c ethylbenzene b a triplet 3 H b quartet 2 H c ~singlet 5 H a
p-diethylbenzene
m-diethylbenzene
o-diethylbenzene
2 -bromo-2 -methylbutane b CH 3 CCH 2 CH 3 a Br c a triplet 3 H b singlet 6 H c quartet 2 H b & c overlap
di-n-propylether a b c c b a CH 3 CH 2 -O-CH 2 CH 3 a triplet 6 H b complex 4 H c triplet 4 H
1 -propanol a b d c CH 3 CH 2 -OH a b c d triplet 3 H complex 2 H singlet 1 H triplet 2 H
C 11 H 16 a 9 H = 3 CH 3, no neighbors 9 H c 5 H = monosubstituted benzene b 2 H, no neighbors 5 H 2 H
C 4 H 8 Br 2 a = 6 H, two CH 3 with no neighbors (CH 3)2 C— b = CH 2, no neighbors & shifted downfield due to Br 2 H 6 H
C 7 H 8 O c = monosubst. benzene 5 H b = CH 2 c = OH 2 H 1 H
C 4 H 9 Br a doublet 1. 04 ppm b complex 1. 95 ppm c doublet 3. 33 ppm 6 H 1 H 2 H a = two equivalent CH 3’s with one neighboring H (b? ) c = CH 2 with one neighbor H (also b) a CH 3 CHCH 2 Br a b c a 6 H doublet b 1 H complex c 2 H doublet
C 10 H 13 Cl a singlet 1. 57 ppm 6 H b singlet 3. 07 ppm 2 H c singlet 7. 27 ppm 5 H a = two-equilalent CH 3’s with no neighbors c = monosubstituted benzene ring b = CH 2
13 C – nmr 13 C ~ 1. 1% of carbons 1) number of signals: how many different types of carbons 2) splitting: number of hydrogens on the carbon 3) chemical shift: hybridization of carbon sp, sp 2, sp 3 4) chemical shift: evironment
13 C-nmr 2 -bromobutane a c d b CH 3 CH 2 CHCH 3 Br
mri magnetic resonance imaging This image is copyrighted, and used by kind permission of Joseph Hornak for use in Chem-312. http: //www. cis. rit. edu/htbooks/mri/
- Application of nmr
- Spectroscopy
- Dept nmr spectroscopy
- Advantages of nmr spectroscopy
- P-diethylbenzene nmr
- Nmr spectroscopy diagram
- Nuclear spin quantum number
- "mirabile"
- Magnetic resonance timisoara
- Montchouk
- Effective magnetic moment formula
- Lesson 15 nuclear quest nuclear reactions
- Fisión nuclear vs fision nuclear
- Magnetic permeability of materials
- Magnetic moment and magnetic field relation
- Find flux
- Force on a charged particle
- Vibronic spectra
- Periodic table of spectra
- Electronic spectra of coordination compounds
- Missing order in diffraction
- Aim 6 letters
- Uv spectra of dienes
- Star spectra
- What is racah parameter
- Azza spectra
- Spectra tips
- Introduction to ftir
- Outline spectra
- Atomic emmision spectrum
- Line spectra
- Aromatic ir spectrum
- Spectra sp200
- Emission line spectra
- Correlation diagram in coordination chemistry
- Electronic spectra of polyatomic molecules
- Thomson higher education
- Spectra shropshire
- Ir spectra chart
- Supernova spectra
- Emission and absorption spectra grade 12
- C triple bond n ir spectra
- Mnova stacked spectra
- Uv spectra of dienes
- Wave frequencies
- Sp2 carbon ir spectrum
- Atomic emission spectra periodic table
- Microstate table for p2
- Aniline ir
- Introduction to atomic spectra
- What is the mulliken symbols for f spectroscopic term in
- Why are atomic emission spectra discontinuous
- Atomic emission spectra and the quantum mechanical model
- Vibrational spectra of metal carbonyls
- Microwave spectroscopy