Tetramethylsilane (TMS) is used as the standard reference compound 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 that makes it suitable for this purpose?
The silicon atom is highly electronegative, which deshields the methyl protons and positions the reference peak downfield of most organic signals.
It has a high boiling point of over 150 ∘C150\text{ }^\circ\text{C}150 ∘C, preventing loss of the reference standard by evaporation during analysis.
It contains twelve equivalent protons and four equivalent carbon atoms, providing a single, intense calibration peak in both 1H^1\text{H}1H and 13C^{13}\text{C}13C NMR spectra.
It is chemically reactive, allowing it to bond reversibly with the analyte to ensure uniform calibration throughout the solution.
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.