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1H-NMR spectra interpretation
Examples , Tables and Problems
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Nuclear Magnetic Resonance
1H-nmr spectrum: Chemical Shift
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How 1H NMR spectrum for p-xylene will appear?
How many H type are their? This will inform us the number of signals in the spectra How many H atoms in each type? This will inform us the area of each signal What are the functional groups near each H type? This will inform us where the signal will appear (chemical shift d) How many H atoms are attached to the carbon atom s nearby each H type? This will inform us how the splitting pattern will appear for each signal
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How 1H NMR spectra for p-xylene will appear?
b a 6H at about 2.2 ppm singlet b 4H at about 7.0 ppm singlet
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How 1H NMR spectra for tert-butyl bromide will appear?
a singlet 9H at about 1.8ppm
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How 1H NMR spectra for ethyl bromide will appear?
a b CH3CH2-Br a triplet 3H b quartet 2H ethyl bromide
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Draw the chemical structure for the compound
Number of signals in the spectra will inform us the number of H type in the molecule Area of each signal will inform us the number of H atoms in each type Chemical shift d of the signal will inform us about closeness of H type to the functional group Splitting pattern for each signal will inform us how many H atoms surrounding each type
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Draw the chemical structure for the compound C3H7Br
a triplet H b complex 2H c triplet H c b a
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Draw the chemical structure for the compound C3H7Br
C3H7Br has IHD = 0 no unsaturation (no double bonds nor cycles), so it is chain molecule (straight or branched). From the given data, there are three signals (a, b and c) so there are three types of H atoms, each type will be at a unique carbon atom. It is obvious that there is no symmetry in the molecule, the formula has 7H atoms and they are distributed on three separate signals (3+2+2). We have CH3-, -CH2- and -CH2- c signal has the higher d value (more deshielded atoms), this mean that this H type of atoms are the nearest to the Br atom. We could use tables to check for this, so c signal should be like this -CH2-Br The splitting pattern shows that a signal is triplet, this mean that it has only 2H atoms surrounding it, so this side of the molecule will be CH3-CH2- because it has only one side to attach with. Now, the final touch, the like between the tow ends, it is the b hydrogens. This will form CH3-CH2-CH2-Br. This justify the splitting patterns for b and c. a b c c a a b c
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Draw the chemical structure for the compound C3H7Br
1-bromopropane a b c CH3CH2CH2-Br a triplet 3H b complex 2H c triplet H
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Try the same methodology for C3H7Cl spectra below
a doublet 6H b septet H b a Answer: isopropyl chloride
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Draw the chemical structure for the compound C4H9Br
a triplet H b doublet 3H c complex 2H d sextet H
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Draw the chemical structure for the compound C8H9Cl
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Draw the chemical structure for the compound C2H6O
a triplet 3H b singlet 1H c quartet 2H
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Draw the chemical structure for the compound C8H10
a triplet 3H b quartet 2H c ~singlet 5H
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Draw the chemical structure for the compound C6H14O
a triplet H b complex 4H c triplet H
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Draw the chemical structure for the compound C10H14
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Draw the chemical structure for the compound C5H11Br
a triplet 3H b singlet 6H c quartet 2H b & c overlap
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Draw the chemical structure for the compound C3H8O
a triplet 3H b complex 2H c singlet 1H d triplet 2H
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Draw the chemical structure for the compound C11H16
a 9H = 3CH3, no neighbors c 5H = monosubstituted benzene b 2H, no neighbors 9H 2H 5H
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Draw the chemical structure for the compound C4H8Br2
a = 6H, two CH3 with no neighbors (CH3)2C— b = CH2, no neighbors & shifted downfield due to Br 2H
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C7H8O c = monosubst. benzene b = CH2 c = OH 5H 2H 1H
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