Two- Dimensional NMR OR

2-D NMR

Mussawir Ali MirzaRoll No. 16

University of Punjab

OBJECTIVES

1) 1-D NMR Principle Sequence Scheme Name Proposed

2) 2-D NMR Principle Sequence Scheme Name proposed shapes of Signal Why 2D NMR Types

1-D NMR• Simple FT-NMR Technique

• 1-D NMR spectroscopy is simple technique In which we provide 90 degree pulse to sample which is placed in uniform magnetic field. As a result we get a FID signal (raw form). To get meaningful data we apply Fourier Transform program on FID to get desire signal.

• Data in form of frequency vs intensity is plotted along x-axis and y-axis respectively

1-D NMR

Sequence Scheme

If we divide the 1-D NMR into a general periods , we get two steps•Preparation•DetectionPreparation : (do something with nuclei)What we can do ??? •Simply we provide a 90 degree pulseDetection: ( detect the signal)•Simply we measure the signal

1D NMR

Pulse Sequence Scheme

Spectrum (EtOH)

Why Named 1-D NMR ??

• We call it 1-D NMR , not because of graph. Graph is actually in 2-d.

• Since one of the time domain is changing into frequency dimension, That’s why we call it 1D NMR,

Time dimension changing into frequency dimension

2-D NMR

• The first two-dimensional experiment was proposed by Jean Jenner.

• 2D NMR is a set of nuclear magnetic resonance spectroscopy (NMR) methods which give data plotted in a space defined by two frequency axes rather than one.

• 2D NMR spectra provide more information about a

molecule than one-dimensional NMR spectra.

Principle

• 2D NMR is Nuclear magnetic resonance spectroscopy in which we provide a 90 degree pulse to our sample which is placed in uniform magnetic field then we wait for (0ms-5ms) depending upon the experiment type then again we provide again 90 degree pulse and this time we measure signal as FID.

• As a result we get Two FID signals which are plotted with respect to time domain.

• To get a meaningful data , we apply Fourier transform program on FIDs to get frequency in terms of ppm.

1. Primary 2D matrix consists a series of FIDs.

2. A set of 1D NMR spectra is obtained by Fourier transformation with respect to t2

3. The signals of each transformation may differ in amplitude and phase. A second Fourier transformation with respect to t1 yields the final 2D matrix with frequency axes F1 and F2

1. 2. 3.

2D NMR

2D NMR Spectrum

PreparationPreparation:: 90 degree pulse excite nuclei in sample.

Evolution Evolution (t1): let them nuclei precess freely.

MixingMixing: again 90 degree r.f. pulses are applied and create transverse magnetizationDetectionDetection (t2): observable transverse magnetization is recorded.

It is usually labeled with t2

Four periods in 2D experiment

2D NMR

Pulse Sequence

How 2D Spectrum is Recorded

How Data is Proceeded

Shapes of Signal

Signal Shapes

Signal Shapes

Double absorption Line

Why 2D NMR

• As 1D NMR spectrum of Macromolecules is quite complex.

• So make this complex spectrum easy, we use 2D NMR.

Types of 2D NMR

• Homonuclear Experiment : In this experiment we provide two frequency to same nuclei in sample. i.e. H-H Correlation spectroscopy (COSY) Actually in it we basically see homonuclear connectivity between same nuclei.

• Heteronuclear Experiment : In this experiment wo provides two frequency to different nuclei in the sample i.e. H-C Heteronuclear Correlation (HETCOR).

H-H COSY Spectrum

H-H COSY Spectrum

HETCOR Spectrum

Thank you !!!!!