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Spectroscopy

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Question 9

Tetramethylsilane (TMS) is used as the universal internal reference standard for calibrating chemical shifts in both 1H^1\text{H}1H and 13C^{13}\text{C}13C NMR spectroscopy. Which statement correctly describes a property of TMS and explains why it is suitable for this purpose?

It has a high boiling point of over 150 ∘C150\ ^\circ\text{C}150 ∘C, which prevents the loss of the reference standard by evaporation during long, multi-hour spectral acquisitions.

Its 12 protons and 4 carbon atoms are highly shielded, producing a single, intense peak that appears upfield of almost all organic signals, defined as δ=0 ppm\delta = 0\text{ ppm}δ=0 ppm.

It is highly hydrophilic and miscible with aqueous solvents like D2O\text{D}_2\text{O}D2​O, ensuring a homogeneous mixture when analyzing highly polar biomolecules.

It acts as a weak nucleophile, forming temporary coordinate bonds with the analyte molecules to stabilize their chemical environments during resonance.

Spectroscopy Questions

  1. A Level
  2. /Chemistry
  3. /Spectroscopy