In problems 4.28 to 4.51, refer to Table 4.3 for isotopic abundances where needed.

Account for the fact that the ²⁹Si NMR spectrum of a mixture of SiCl₄ and SiBr₄ that has been standing for 40 h contains five singlets which include those assigned to SiCl₄ (δ –19 ppm) and SiBr₄ (δ – 90 ppm).

Table 4.3

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Nucleus ΤΗ ²H Li 11B 13C 170 19 F 23 Na 2 Al 29 Si 31 p 7 Se 103 Rh 117. Sn 119 Sn 19 Xe 183 W 195 pt 199 Hg Natural abundance/% >99.9 0.015 92.41 80.1 1.07 0.04 100 100 100 4.69 100 7.63 100 7.68 8.59 26.40 14.31 33.78 16.87 miele v + mk nh -k -le -le-le - -ki -k -k -IN Frequency of observation / MHz (referred to ¹H at 100 MHz) 100 15.35 38.9 32.1 25.1 13.5 94.0 26.45 26.1 19.9 40.5 19.1 3.2 35.6 37.3 27.7 4.2 21.5 17.9 Chemical shift reference (8 0 ppm)* SiMe SiMe4 LICI (1 M in H₂O) F3B-OEt2 SiMe H₂O CFC13 NaCl (1 M in H₂O) [Al(OH₂)]³+ SiMc4 H3PO4 (85%, aq) SeMe₂ Rh (metal) SnMc4 SnMe4 XeOF4 Na₂WO4 (in D₂O) Na₂ [PtCl6] HgMe₂