Question

Pre-Lab Questions 1. What are some common solvents used in NMR sample preparation? 2. Are all molecules able to be analyzed using proton NMR? Explain. 3. Compare NMR radiation to X-ray radiation in terms of energy, wavelength, and frequency 4. What do the terms upfield and downfield indicate on an NMR spectrum? 5. You overheard a classmate state that they did not want to run a sample in an NMR because the radiation would destroy their sample by 'breaking bonds'. Does your classmate have a valid point? Explain.

Answer 1

Solution:-

1. Common solvents such as  chloroform-D, acetone-D6, benzene-D6, deuterium oxide (D₂O), DMSO-D6, ethanol-D6, and methanol-D4. etc.

2. Not all nuclei are accessible by the NMR experiment.

The electron(s) surrounding the proton in covalent compounds and ions. Since electrons are charged particles, they move in response to the external magnetic field (B_o) so as to generate a secondary field that opposes the much stronger applied field. This secondary field shields the nucleus from the applied field, so external magnetic field must be increased in order to achieve resonance (absorption of rf energy). External magnetic field B_o must be increased to compensate for the induced shielding field.Those compounds that give resonance signals at the higher field side such as CH₄, HCl, HBr and HI have proton nuclei that are more shielded than those on the lower field (left) side such as H atom ,H₂SO4,CHCl₃

3.

NMR Radiation	X-Ray Radiation
A magnetic field, NMR active nuclei (such as 1H or 13C) absorb electromagnetic radiation at a frequency characteristic of the isotope.	X-rays are a form of electromagnetic radiation similar to radio waves, microwaves, visible light and gamma rays. X-ray photons are highly energetic and have enough energy to break up molecules and hence damage living cells.
The energy transfer takes place at a wavelength that corresponds to radio frequencies and when the spin returns to its base level, energy is emitted at the same frequency.	X - rays is a form of electromagnetic radiation. Most X - rays have a wavelength ranging from 0.01 to 10 nm .
Usually given as a frequency in units of MHz (106 Hz), ranging from 20 to 900 Mz, depending on the magnetic field strength and the specific nucleus being studied.	X-rays are electromagnetic waves with wavelengths in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz

4.

When looking downfield of an NMR spectrum, you are looking at the peaks that are on the left side of the spectrum in which the ppm is increasing. When looking upfield, you are looking at the peaks that are on the right side of the spectrum in which ppm is decreasing.