Tritium nuclear magnetic resonance spectroscopy. Part 11. Further consideration of referencing, isotope effects and coupling constants: Preparation of [ 3 H]tetramethylsilane

Small discrepancies between 3 H and 1 H chemical shifts in organic compounds led to the finding that the ratio of Larmor frequencies ω T /ω H depends on the carbon‐hydrogen bond hybridisation. The ‘best’ ratio for ghost referencing of 3 H NMR spectra was then determined from measurements on purified partially tritiated TMS as 1.066639738±2 × 10 −9 . Some 3 H isotope effects on chemical shifts are listed and the 3 H isotope effect on the methylene geminal coupling constant in benzyl methyl sulphoxide is measured. Use of 2 H in the measurement of 2 J (HH) coupling constants has inherent disadvantages, overcome by use of 3 H substitution.