Question

2. In NMR spectroscopy the different types of hydrogen atoms in a molecule A. absorb at slightly different radio frequencies. B. produce signals observed at different chemical shifts. c. produce signals measured relative to that of TMS. D. all of these.

Answer 1

The answer is all of the above i.e., option D.

Explanation:

In NMR we exite the nuclei sample into nuclear magnetic resonance with the help of radio waves to produce NMR signals. These NMR signals are detected with sensitive radio receivers. The resonance frequency of an atom in a molecule is changed by the intramolecular magnetic field surrounding it. With different environment they give signals at different chemical shift. And in NMR we use TMS as standard solution with refer to this different proton give different absorption peak at different frequency. Because of its high volatility, TMS can easily be evaporated, which is convenient for recovery of samples analyzed by NMR spectroscopy. Because all twelve hydrogen atoms in a tetramethylsilane molecule are equivalent, its 1H NMR spectrum consists of a singlet. Tetramethylsilane became the established internal reference compound for 1H NMR because it has a strong, sharp resonance line from its 12 protons, with a chemical shift at low resonance frequency relative to almost all other 1H resonances. Thus, addition of TMS usually does not interfere with other resonances.

Thus we can say that option D is correct.