Practice question

Tetramethylsilane is ideal reference because its twelve protons are magnetically equivalent, producing intense sharp singlet due to strong shielding by electropositive silicon and methyl electron donation. Chemically inert, volatile, and soluble in organic solvents, TMS does not interact with analytes and evaporates easily. Resonance is defined as zero ppm, anchoring chemical shift scale. In aqueous biomolecular NMR, water-soluble analogs like DSS or TSP are used, but principle remains same. Referencing allows reproducible assignment of protein side chains and metabolite peaks across different spectrometers and laboratories.