2D-NMR-Athar-P-1 (1)

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    1

    2D-

    NUCLEAR MAGNETIC RESONANCESPECTROSCOPY

    Part-1

    Dr. M. Athar Abbasi

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    THE PRINCIPLE OF 2D-NMR SPECTROSCOPY

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    GENERAL SCHEME FOR 2D-NMR

    In 1D pulsed Fourier transform NMR the signal is recorded as a

    function of one time variable and then Fourier transformed to givea spectrum which is a function of one frequency variable.

    In 2D-NMR the signal is recorded as a function of two time

    variables, t1

     and t2

     , and the resulting data Fourier transformed

    twice to yield a spectrum which is a function of two frequency

    variables.

    The general scheme for two dimensional spectroscopy is

    In the first period, called the preparation time, the sample is  excited by one or more pulses. The resulting magnetization isallowed to evolve for the first time period, t1

     .

    Then another period follows, called the mixing time, which

    consists of a further pulse or pulses. After the mixing period thesignal is recorded as a function of the second time variable, t2.

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    This sequence of events is called a pulse sequence and the exact

     nature of the preparation and mixing periods determines theinformation found in the spectrum.

    It is important to realize that the signal is not recorded during the

    time t1

     , but only during the time t2

     at the end of the sequence. The

    data is recorded at regularly spaced intervals in both t1

     and t2

     .

    The two-dimensional signal is recorded in the following way. First,

    t1

     is set to zero, the pulse sequence is executed and the resulting

    free induction decay recorded. Then the nuclear spins are allowed

    to return to equilibrium. t1

     is then set to 1, the sampling interval

    in t1

     , the sequence is repeated and a free induction decay is

    recorded and stored separately from the first. Again the spins are

    allowed to equilibrate, t1

     is set to 2 1, the pulse sequence

    repeated and a free induction decay recorded and stored. Thewhole process is repeated again for t1

     = 3 1, 4 1 and so on until

    sufficient data is recorded, typically 50 to 500 increments of t1

     .

    Thus recording a two-dimensional data set involves repeating a

    pulse sequence for increasing values of t1

     and recording a free

    induction decay as a function of t2 for each value of t1.

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    TWO-DIMENSIONAL NMR PULSE SEQUENCE

    Fig. 2D J-Resolved NMR spectroscopy; the evolution time t1 is gradually

    increased while the detection time t2 is kept constant.

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    Fig. Basic pulse sequence for 2D acquisition

    2D Fourier transformThe FID is then Fourier transformed in both directions (fig. 2) to

    yield the spectrum. The spectrum is conventionally displayed as a

    contour diagram. The evolution frequency is labeled f 1 and the

    acquisition frequency is labeled f 2 and plotted from right to left.

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    PLOTTING 2D-NMR SPECTRUM

    Conventional NMR spectra (1D-

     spectra) are plots of intensity vs.

    frequency; in 2D-  spectroscopy intensity is plotted as a functionof two frequencies, usually called F1 

    and F2

     .

    There are various ways of representing such a spectrum on paper,

     but the one most usually used is to make a contour plot in which  the intensity of the peaks is represented by contour lines drawn  at

    suitable intervals, in the same way as a topographical map.

    The position of each peak is specified by two frequency co-

     ordinates corresponding to F1  and F

    2

     .

    2D-NMR spectra are always arranged so that

    the F2

     

    co-ordinates of the peaks correspond

    to those found in the normal 1D-

     spectrum,

    and this relation is often emphasized byplotting the 1D-

     spect. alongside the F2

     axis.

    The figure shows a schematic COSY

    spectrum of a hypothetical moleculecontaining just two protons, A and X, which

    are coupled together.

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    The one-dimensional spectrum is plotted alongside the F2

     axis,

    and consists of the familiar pair of doublets centred

     on the

    chemical shifts of A and X, δA and δX

     respectively.

    In the COSY spectrum, the F1

     co-ordinates of the peaks in the two-

     dimensional spectrum also correspond to those found in the  normal one-dimensional spectrum and to emphasize this point theone dimensional spectrum has been plotted alongside the F1 axis.

    It is immediately clear that this COSY spectrum has some

    symmetry about the diagonal F1

     = F2

     which has been indicated

    with a dashed line.

    In a 1D-

     spectrum scalar couplings give rise to multiplets

     in the

    spectrum. In 2D-

     spectra the idea of a multiplet

     has to be

    expanded somewhat so that in such spectra a multiplet

     consists

    of an array of individual peaks often giving the impression of a

     square or rectangular outline.

    The appearance in a COSY spectrum of a cross-peak multiplet

     F1

     =

    δA, F2 = δX  indicates that the two protons at shifts δA and δX  havea scalar coupling between them.

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    ADVANCED NMR TECHNIQUES

    ONE DIMENSIONAL NMR TECHNIQUES

    DEPT  [Distortionless  Enhancement (of NMR Signals) byPolarization Transfer]A procedure which enhances the intensities of 13C signals and

    also provides information on the number of attached protons.

    Quaternary carbons are not observed. The 135o

     pulse results inpositive signals for CH and CH3 

    groups and negative signals for

    CH2

     groups. The 90o

     pulse results in positive signals for CH

    groups and null signals for CH2

     and CH3

     groups. The 45o

     pulse

    results in positive signals for CH, CH2

     and CH3

     groups.

    INEPT

     (Insensitive Nuclei Enhanced by Polarization Transfer)

    A precursor to DEPT that gives similar results, although often not

    as well.

    NOE

     (Nuclear Overhauser 

     Enhancement)

    Irradiation at specific frequencies before signal aquisition

     enhances the intensities of nearby nuclei. Nearby nuclei inducerelaxation, which leads to signal enhancement, through dipole-  dipole interactions. The effect usually diminishes as a function  

    of

    1/r6.

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    TWO DIMENSIONAL NMR TECHNIQUES

    NOESY

     (Nuclear Overhauser 

     Enhancement Spectroscopy)

    The 2D version of the NOE experiment yields a display of all

    atoms that are close in space. The diagonal and the projection on

    each axis are the one-dimensional spectrum. The off-diagonal

    peaks indicate Overhauser 

     Enhancements between pairs of 

     protons.

    ROESY

     (Rotating Frame Overhauser 

     Enhancement Spectroscopy)

    Advanced form of NOESY ideal for large molecules.

    COSY

     (Correlated Spectroscopy)

    A 2D experiment that yields a display of all coupled protons. The

    diagonal and the projection on each axis are the one-dimensional

    spectrum. The off-diagonal peaks indicate the presence of 

     coupling between pairs of protons.

    COLOC

     (Correlated Spectroscopy for Long-Range Couplings)

    Experiment correlating the 13C spectrum on one axis and 1H

    spectrum on the other. Cross peaks indicate long-range C-Hconnectivity.

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    SECSY

     (Spin Echo Spectroscopy)

    Technique that yields the same information as the COSY

    procedure, but with a different display format.

    EXTASY

     (Exchange Inter action Spectroscopy)

    Useful procedure for determining sites that undergo chemical

    exchange.

    J-Resolved 2D NMR

    A 2D technique that results in the normal spectrum projected on

    one axis and coupling projected on to the other axis.

    HETCOR

     (Heteronuclear 

     Shift Cor relation)

    Experiment correlates the 13C spectrum on one axis and 1H

    spectrum on the other. Cross peaks indicate C-H connectivity.

    HMBC

     (Heteronuclear 

     Multiple Bond Correlation)

    Advanced inverse detected experiment correlating the 13C

    spectrum on one axis and 1H spectrum on the other. Cross peaks

    indicate long-range C-H connectivity.

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    HMQC

     (Heteronuclear 

     Multiple Quantum Coherence)

    Advanced inverse detected version of HETCOR. Experiment

    correlates the 13C spectrum on one axis and 1H spectrum on the

    other. Cross peaks indicate C-H connectivity.

    HOHAHA

     (Homonuclear 

     Hartmann Hahn)

    Experiment that takes COSY a step further by correlating protons

     with small coupling constants as occurs with long range coupling.Identifies spin sets, similar to TOCSY.

    INADEQUATE

     (Incredible Natural Abundance Double Quantum

    Transfer Experiment)

    Procedure used to directly obtain carbon-carbon connectivities

     and, ultimately, the carbon skeleton of a molecule.

    INSIPID

     (Inadequate Sensitivity Improvement by Proton Indirect

    Detection)

    A reverse detection INADEQUATE experiment that greatly reduces

    the aquisition

     time.

    TOCSY

     (Total Correlation Spectroscopy)

    Experiment that takes COSY a step further by correlating protons  with small coupling constants as occurs with long range coupling.Identifies spin sets, similar to HOHAHA.

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    STRUCTURE ELUCIDATION

    1H-NMR.

    Information about protons.

    Integration shows number of protons.

    Splitting shows how many protons onadjacent carbons, and chemical shift

    shows shielding.

    H3C

    CH

    H3C

    CH2

    OH

    0.92, d

    0.92, d 3.39, d

    2.59, s (variable)1.77, m

    (9 peakes)

    0.92, d

    1.77, m

    2.59, s

    (variable)

    3.39, d

    Decoupled 13C-spectrum.

    No splitting. Chemical shift for

    identification. Integration not valid

    unless data collected under specialconditions.

    H3C

    CH

    H3C

    CH2

    OH18.80

    18.80

    30.80

    69.60 ISOBUTANOL

    Integration

    18.8030.8069.60

    77.0(CDCl3

     

    )

    Solvent (CDCl3

     

    ). 77.0 ppm.Identified by chemical shift

    and splitting. Deuterium has

    spin quantum number 1 (3

    spin states). Splits carbon to

    three equal peaks.

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    ATP. Attached Proton Test.Used to determine the number of

    protons attached to each carbon.

    Carbons with an even number of

    protons (C and CH2

     ) go one direction.Carbons with an odd number of

    protons (CH and CH3

     

    ) go the other. In

    this spectrum, even protons go up and

    odd protons go down.

    DEPT 45. Distortionless

     Enhancement

    by Polarization Transfer.

    This experiment with a 45 degree

    decoupler 

     pulse gives a spectrum where

    all carbons with attached protons areobserved. Quaternary carbons (with no

    protons) are not observed. The

    experiment is used in conjunction with

    the DEPT 90 and DEPT 135

    experiments to identify number ofprotons attached to each carbon.

    18.80CH3

    30.80

    CH

    69.60

    CH277.0

    (CDCl3

     

    )

    This peak is up so it is for

    a carbon with an even

    number (0) of proton. 18.80

    30.80

    69.60

    These peaks are for carbons with

    attached protons.

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    DEPT 135.This experiment with a 135 degree

    decoupler 

     pulse gives a spectrum

    where CH and CH3

     

    carbons are up, CH2carbons are down, quaternary carbons

    are not observed. The experiment isused in conjunction with the DEPT 45

    and DEPT 90 experiments to identify

    number of protons attached to each

    carbon.

    DEPT 90.This experiment with a 90 degree

    decoupler 

     pulse gives a spectrum

    where CH carbons are observed. C,

    CH2

     and CH3

     carbons are not

    observed. The experiment is used in

    conjunction with the DEPT 45 and

    DEPT 135 experiments to identify

    number of protons attached to each

    carbon.

    69.60

    CH2

     

    . A small peak is observed, but it is

    much smaller in this spectrum. Shows that

    this carbon is not a CH. Since it is

    observed in the DEPT 45 it is also not a

    quaternary carbon. The DEPT 135

     distinguishes between remaining choices.

    30.80CH3

     

    . A small peak is observed, but it is

    much smaller in this spectrum. Shows

    that this carbon is not a CH. Since it is

    observed in the DEPT 45 it is also not a

    quaternary carbon. The DEPT 135

    distinguishes between remaining choices.

    CH. This peak is

    observed at about

    the same intensity

    as in the DEPT

    45, this show

     

    s

    that it is a CH

    carbon.

    18.80

    18.80

    30.80

    69.60

    CH2

     

    . This peak is down

    so it is a CH2

     

    carbon.

    CH. Since this peak is up it must be a CH3

     

    or

    CH, since it was present in the DEPT 90, it isa CH carbon.

    CH3

     

    . This peak is up, but is not observed in

    the DEPT 90 so it must be a CH3

     

    carbon.

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    COSY. Correlation Spectroscopy.

    This experiment shows proton-proton

    correlation (which protons are coupled

    to which). Coupled protons are typically

    on adjacent carbons.

    HETCOR. Heteronuclear 

     Correlation

    Spectroscopy.

    This experiment shows how protons

    and carbons are coupled. Since

    carbons are most strongly coupled toattached protons, this experiment

    shows which protons are attached to

    which carbons. This is useful for

    assigning peaks in one spectrum if it isidentified in the other.

    CH2

     

    CH cross peaks.

    This peak shows that

    the CH2

     

    protons are

    coupled to the CH

    proton.

    3.39 1.77

    0.92

    CH3

     

    CH cross peaks. This peak

    shows that the CH3

     

    protons are

    coupled to the CH proton.

    0.92

    1.773.39

    69.60

    30.80

    18.80

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    PAMOIC ACID

    CH2

    OH

    O

    OH

    OH

    OH

    O

    12

    345

    6

    7   8 9

    10

    HH

    H

    H

    H

    7.9, d

    J = 7.9 Hz

    7.2, t

    J = 7.9 Hz

    7.4, t

    J = 7.9 Hz

    8.1, d

    J = 7.9 Hz 4.8, br s

    8.5, s

    1'2'

    3'4'5'6'

    7'8'

      9'

    10'

    11

    12

    12'

    Integration*

    8.5, s

    1H-NMR.

    * Integration is not helpful since the molecule has two

    similar ring systems, all the protons have an integration of 2.

    Proton 1. No splitting. Integration 2. Identified by chemical shift (ring

    proton) and splitting (only other proton with no splitting is the CH2

     

    ).

    8.1,

    d

    Proton 5. 8.5 ppm

     shift. No splitting. Integration 2. Identified as a ring proton by chemical shift. Doublet splitting is

    consistent with Proton 5 or 8. NOE experiment is required to distinguish between position 5 and 8 (See NOESY data).

    Proton 8. 7.9 ppm

     shift. Doublet. Integration 2. Identified as a ring proton by chemical shift. Doublet splitting is

    consistent with Proton 8 or 5. NOE experiment is required to distinguish between position 8 and 5 (See NOESY data).

    7.9,

    d

    Proton 6. 7.4 ppm

     shift. Triplet. Integration 2. Identified as a ring proton by chemical shift. Triplet splitting is consistent

    with Proton 6 or 7. NOE experiment is required to distinguish between position 6 and 7 (See NOESY data for

    experimental results identifying this proton.

    7.4, t

    Proton 7. 7.2 ppm

     shift. Triplet. Integration 2. Identified as a ring proton by chemical shift. Triplet splitting is consistent

    with Proton 6 or 7. NOE experiment is required to distinguish between position 6 and 7 (See NOESY data).

    7.2, t

    CH2

     

    protons. 4.8 ppm

     shift. No splitting. Integration 2. Identified by chemical shift (not a ring proton) and splitting

    (only other proton with no splitting is on the ring).

    4.8, br 

     s

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    Decoupled carbon spectrum.

    CH2

    OH

    O

    OH

    OH

    OH

    O

    12

    3456

    7   8 9

    10

    173.0

    114.6

    131.9

    153.8

    121.0136.6123.8

    123.72

    129.3

    1'2'3'

    4'

    9'10'

    5'6'

    7'8'

    130.6127.2

    20.4

    173.0 ppm. Carboxylic acid carbon. Based on chemical shift. Not observed in DEPT-45spectrum so consistent with quaternary carbon.

    153.8 ppm. Carbon 3. Not observed in DEPT-45 spectrum so must be quaternary carbon.

    Chemical Shift is consistent with an aromatic carbon with -OH attached.

    136.6 ppm. Carbon 10. Not observed in DEPT-45 spectrum so must be quaternarycarbon. Assignment is consistent with predicted chemical shift. Chemical shift is not

    conclusive (difficult to distinguish between C-9 and C-10). Verified assignment would

    require additional experiments (COLOC to show coupling to CH2

     

    proton would be useful).

    131.9 ppm. Carbon #1. Observed in all DEPT spectra so must be a CH carbon. Hetcor 

     shows coupling to proton #1.

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    130.6 ppm. Carbon #8. Observed in all DEPT spectra so must be a CH carbon. Hetcor 

     shows coupling to proton #8.129.3 ppm. Carbon #6. Observed in all DEPT spectra so must be a CH carbon. Hetcor 

     shows coupling to proton #6.127.2 ppm. Carbon 9. Not observed in DEPT-45 spectrum so must be quaternary carbon.

     Assignment is consistent with predicted chemical shift. Chemical shift is not conclusive

    (difficult to distinguish between C-9 and C-10.) Verified assignment would require

    additional experiments (COLOC to show coupling to adjacent carbons would be useful, but

    complicated by aromatic ring.)

    123.8 ppm. Two peaks are resolved. Peak at 123.80 is Carbon # 5. Peak at 123.72 is

    Carbon #7. Both are observed in all DEPT spectra so must be a CH

     carbon. Both are

    identified from coupling in Hetcor.

    121.0 ppm. Carbon #4. Not observed in DEPT-45 spectrum so must be quaternary carbon.

     Assignment is consistent with predicted chemical shift. Chemical shift is not conclusive

    (difficult to distinguish between C-4 and C-2.) Verified assignment would require additional

    experiments (COLOC to show coupling to CH2

     

    proton would be useful).

    114.6 ppm. Carbon #2. Not observed in DEPT-45 spectrum so must be quaternary carbon. Assignment is consistent with chemical shift for aromatic carbon

     with carboxylic acid.

    Chemical shift is not conclusive (difficult to distinguish between C-4 and C-2.) Verified

    assignment would require additional experiments (COLOC to show coupling to proton #1

    would be useful).

    20.4 ppm. CH2

     

    Carbon. Only C-

     with chemical shift in this region. Observed in DEPT-45,

    Not observed in DEPT-90, and inverted phase in DEPT-135 so must be a CH2 carbon.

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    DEPT 45. Distortionless

     Enhancement

    by Polarization Transfer.This experiment with a 45 degree

    decoupler 

     pulse gives a spectrum where

    all carbons with attached protons are

    observed. Quaternary carbons (with noprotons) are not observed. The

    experiment is used in conjunction with the

    DEPT 90 and DEPT 135 experiments to

    identify number of protons attached to

    each carbon.

    131.9 ppm. Carbon #1. Observed in all

    DEPT spectra so must be a CH carbon.

    Hetcor 

     shows coupling to proton #1.

    130.6 ppm. Carbon #8. Observed in allDEPT spectra so must be a CH carbon.

    Hetcor 

     shows coupling to proton #8.

    129.3 ppm. Carbon #6. Observed in all

    DEPT spectra so must be a CH carbon.Hetcor 

     shows coupling to proton #6.

    129.3 ppm. Carbon #6. Observed in all

    DEPT spectra so must be a CH carbon.

    Hetcor 

     shows coupling to proton #6.

    123.8 ppm. Two peaks are resolved.

    Peak at 123.80 is Carbon # 5. Peak at

    123.72 is Carbon #7. Both are observed

    in all DEPT spectra so must be a CH

    carbon. Both are identified from coupling

    in Hetcor.

    20.4 ppm. CH2

     

    Carbon. Only carbon with

    chemical shift in this region. Observed in

    DEPT-45, Not observed in DEPT-90, andinverted phase in DEPT-135 so must be

    a CH2 carbon.

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    DEPT 90.

    This experiment with a 90 degree decoupler pulse gives a spectrum where CH carbons

    are observed. C, CH2

     

    and CH3

     

    carbons are

    not observed. The experiment is used in

    conjunction with the DEPT 45 and DEPT135 experiments to identify number of

    protons attached to each carbon.

    131.9 ppm. Carbon #1. Observed in all

    DEPT spectra so must be a CH carbon.

    Hetcor 

     shows coupling to proton #1.

    130.6 ppm. Carbon #8. Observed in all

    DEPT spectra so must be a CH carbon.

    Hetcor 

     shows coupling to proton #8.

    129.3 ppm. Carbon #6. Observed in all

    DEPT spectra so must be a CH carbon.

    Hetcor 

     shows coupling to proton #6.

    123.8 ppm. Two peaks are resolved.

    Peak at 123.80 is Carbon # 5. Peak at

    123.72 is Carbon #7. Both are observed

    in all DEPT spectra so must be a CHcarbon. Both are identified from coupling

    in Hetcor.

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    HETCOR. Heteronuclear 

     Correlation

    Spectroscopy.

    This experiment shows how protons and

    carbons are coupled. Since carbons are

    most strongly coupled to attached protons,

    this experiment shows which protons areattached to which carbons. This is useful

    for assigning peaks in one spectrum if it is

    identified in the other.

    (See this region

    expanded

    on next slide)

    4.81 ppm

     H-11 (CH2

     ), 20.4 ppm

     C-11. H-11 peak is identified as CH2

     by chemical shift.

    C-11 is identified as CH2 by DEPT experiment.

    8.50 ppm

     H-1, 131.9 ppm

     C-13. H-1

    peak is a singlet, the only other singlet is

    identified as CH2

     

    , so must be H at

    position 1. C-13 is identified bycorrelation to proton in position 1 in

    HETCOR. In addition, DEPT experiment

    identifies this carbon as having a single

    proton which correlates with correct

    assignment.

    8.14 ppm

     H-1, 123.72 ppm

     C-13. H-1

    peak is identified by splitting (doublet) as

    position 5 or 8, NOESY correlation to

    CH2

     protons at 4.8 ppm

     identifies thispeak (8.14 ppm) as position 5. C-13 is

    identified by correlation to proton at

    position 5 in HETCOR (further expansion

    of HETCOR spectrum clearly

    distinguishes between C-13 peaks at123.7 and 123.8 ppm). In addition, DEPT

    experiments identify this carbon is

    attached to one proton. Consistent with

    assignment.

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    7.9 ppm

     H-1, 130.6 ppm

     C-13. H-1 peak

    is identified by splitting (doublet) as

    position 5 or 8, NOESY correlation to

    position 1 at 8.5 ppm

     identifies this peak(7.9 ppm) as position 8. C-13 is identified

    by correlation to proton at position 8 in

    HETCOR. In addition, DEPT experiments

    identify this carbon is attached to one

    proton. Consistent with assignment.

    7.24 ppm

     H-1, 123.81 ppm

     C-13.

     H-1

    peak is identified by splitting (triplet) as

    position 6 or 7; selective homonuclear 

    decoupling at 7.9 ppm

     causes this peakto collapse to a doublet; since peak at 7.9

    is assigned position 8 by NOESY, this

    peak (7.24 ppm) is identified as position

    7. C-13 is identified by correlation to

    proton at position 8 in HETCOR (furtherexpansion of HETCOR spectrum clearly

    distinguishes between C-13 peaks at

    123.7 and 123.8 ppm). In addition, DEPT

    experiments identify this carbon is

    attached to one proton. Consistent withassignment.

    7.4 ppm

     H-1, 129.3 ppm

     C-13. H-1 peak is

    identified by splitting (triplet) as position 6 or 7;

    Selective Homonuclear 

     decoupling at 8.1 ppm

     causes this peak to collapse to a doublet,since peak at 8.1 is assigned as position 5 byNOESY, this peak (7.4 ppm) is identified asposition 6 (Same information would be

    available from a COSY spectrum). C-13 is

    identified by correlation to proton at position 6

    in HETCOR. In addition, DEPT experiments

    identify this carbon is attached to one proton.Consistent with assignment.

    (Expanded region)

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    COSY Spectrum.

    C. This COSY Cross peak shows the coupling between peaks at 7.2 and 7.4 ppm. This

    is consistent with the coupling between the two triplets for protons 6 and 7.

    A. This COSY Cross peak shows the coupling between peaks at 8.1 and 7.4 ppm. This

    shows the connection between protons 5 and 6 OR between 7 and 8.

     It is not possible to

    distinguish which pair from the COSY spectrum.

    B. This COSY Cross peak shows the coupling between peaks at 7.2 and 7.9 ppm. This

    shows the connection between protons 5 and 6 OR between 7 and 8.

     It is not possible to

    distinguish which pair from the cosy

     spectrum.

     A B

    C

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    NOESY Spectrum.

    A. This NOE cross peak shows the NOE between peaks at 8.5 and 7.9

     ppm. Since the

    peak at 8.5 is a singlet and has a chemical shift consistent with a ring proton, it has been

    assigned proton 1. This peak does not appear in the COSY spectrum, so it must be

    caused by NOE. The NOE peak identifies the peak at 7.9 as proton

     8.

     A

    B CD

    E

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    SYRINGALDEHYDE

    H3CO

    CO

    H

    H3CO

    HO1

    3

    5

    1'

    2'

    3'

    Pale yellowish needles

    Melting point: 113-114o

    Boiling point: 192-193o

    UV λmax

     

    nm (logε) (MeOH):

    303 (4.01), 229.8 (4.15),

    225.8 (4.14), 214.8 (4.20),

    198.4 (3.92) nm 200 nm 250 300 350 400 450

    IRν

    max

     (CHCl3

     ):3282 (OH),

    2923, 2850.5

    (C-H, aldehyde),

    1671 (C=O, ald.),

    1606-1462 (C=C,Ar),1330 (overt. aldehyde

    C-H, bend.),

    1252, 1207 (C-O-C),

    1141, 1109 (C-O)831, 727 cm-1

    4000 3500 3000 2500 2000 1500 1000 500

    Wavenumber 

     cm-1

       T  r  a  n  s  m   i   t   t  a  n  c  e   [   %   ]

    IR Spectrum

    UV spectrum

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    182

    40 60 80 100 120 140 160 180

    166

    153

    139

    123

    m/z

    183

    51.9

    11193.1

    78

    65.1

    10

    20

    30

    40

    50

    60

    70

    80

    90

    0

    %age

    EI-MS

    HR-MS

    EI-MS m/z (rel. int. %):

    182 [M]+

     (100), 153 [M-HCO]

    +

     (10.2),

    123 [M –

     (MeO

     + CO]+

     (6.7)

    HR-MS:

     The molecular formula was

    deduced as C9

     

    H10

     

    O4

     

    through HR-MS,

    showing a [M]+

     ion peak at m/z

    182.04329, (Calcd. for 182.04192), and

    indicating 5 degrees of unsaturation.

    Lit.

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    1H-NMR.The 1H-NMR spectrum displayed a

    singlet at δ 9.80, which is characteristic

    for an aldehyde

     group while a two-

     proton singlet at δ  7.13  revealed the

    presence of a symmetrically substituted

    aromatic ring. Similarly, a six-proton

    singlet at δ 3.89 was assignable to

     two

    magnetically equivalent methoxyl

     groups in the molecule.

    1H-NMR

     (CDCl3

     

    ) (300 MHz) (δ

     ppm):

    9.80 (1H, s, H-1'), 7.13 (2H, s, H-2, H-6), 3.89 (6H, s, OMe-2', OMe-3')

    H3CO

    C

    O

    H

    H3CO

    HO1

    3

    5

    1'

    2'

    3'

    H

    H

    9.80 s

    7.13 s

    7.13 s

    3.89 s

    3.89 s

    9.80, s

    7.13, s

    3.89, s

    Note:

     Some extra peaks show that purity is

    not good. It may be mixture of two isomers.

    0.010.0 1.02.03.04.05.06.07.08.09.0

    ppm

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