2) Part of the 'H NMR spectrum for a dipeptide recorded in D₂O is shown below. The signal for the CH 3 group is not shown. (i) Explain what has happened to the H-atoms attached to the N atoms. (ii) Interpret the spectrum Note the signals for HA and HA are subject to a second order effect. D₂N Ha `N H^H^' L-Ala-Gly 40 Hz H 0.1 ppm

2) Part of the 'H NMR spectrum for a dipeptide recorded in D₂O is shown below. The signal for the CH 3 group is not shown. (i) Explain what has happened to the H-atoms attached to the N atoms. (ii) Interpret the spectrum Note the signals for HA and HA are subject to a second order effect. D₂N Ha `N H^H^' L-Ala-Gly 40 Hz H 0.1 ppm

Organic Chemistry

9th Edition

ISBN:9781305080485

Author:John E. McMurry

Publisher:John E. McMurry

Chapter24: Amines And Heterocycles

Section24.9: Heterocyclic Amines

Problem 21P

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1) The zwitterionic form of leucine has a structure H3C CH 3 H NH₂+ H H H (i) Draw out the structure at pH 1 (ii) Draw out the structure at pH 12 (iii) -COO- Predict which direction the signal for the H on on the α C will move in the ¹H NMR on going from low to high pH. (iv) Explain why this change in chemical shift occurs.
The 1H NMR for a dipeptide recorded in D20 is shown below. (i) Explain what has happened to the H- atoms attached to the N atoms. (ii) Explain the spectra. Note the signals for HA and HA'are subject to a second order effect. H^H* 40 Hz 0.1 ppm 'N- DN Ha L-Ala-Gly (iii) predict which direction the signal for the H on the alpha-C will move in the 1H NMR on going from low to high ph and explain why this leads to a change in chemical shift.
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Show the 1H NMR spectrum for arginine
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