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}D2O, 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.
28 exam-style questions on OCR A A Level Chemistry Spectroscopy. Each one has a worked solution and a mark scheme showing where the marks go.