Example Questions Flashcards
EXAMPLE: NMR Revision
NOTE: There are many more NMR active nuclei in this molecule i.e. the phenyl groups have 13C and 1H NMR
Why don’t we observe coupling to these nuclei?
REMEMBER: 13C is only 1% abundant so only 1 in 100 molecules has:
* Also note that the magnitude of the coupling falls off rapidly with distance (number of bonds)
* Closest phenyl hydrogen = 3 bonds away so any coupling is so much smaller than the 1-bond coupling to the terminal P–H bond – not observed
EXAMPLE: NMR Revision
Explain the Observed 19F NMR spectrum IF5 (iodine pentafluoride)
- Iodine is not spin active, therefore splitting and multiplicity must only be due to 19F nuclei
- Both binomial distributions
EXAMPLE: NMR Revision
Consider the 31P{1H} NMR Spectrum of Pt(PCy)3 [Cy = cyclohexyl]
* Typically given information : 31P: I = 1⁄2, 100 % abundant; 195Pt: I = 1⁄2, 33.8 % abundant
31P NMR
how many environments for 31P?
- 1 x phosphorus environment = 1 signal other spin active nuclei?
1 x platinum (195Pt spin active)
- therefore if apply 2nI + 1 :
= (2 x 1 x 1⁄2) + 1 = 2 (doublet)
EXAMPLE: NMR Revision
Predict the 1H NMR Spectrum of Sn(CH3)4
Typically given information : 117Sn: I = 1⁄2, 7.68 % abundant; 119Sn: I = 1⁄2, 8.59 % abundant
EXAMPLE: Inorganic NMR
How many energy levels will nuclei with I = 3/2 split in to?
What would the 11B NMR Spectrum of BH4 look like?
* Typically given information : 11B: I = 3/2, 80.4 % abundant; 1H: I = 1⁄2, 99.9 % abundant
EXAMPLE: Boranes
What would the 11B NMR Spectrum of LBH3 look like and how would it compare to [L2BH2] [BH4]?
* Typically given information : 11B: I = 3/2, 80.4 % abundant; 1H: I = 1⁄2, 99.9 % abundant;
EXAMPLE: Boranes
What structure would [B6H6]2- be?
EXAMPLE: Boranes
What structure would B5H9 be?
EXAMPLE: Boranes
What structure would B4H10 be?
EXAMPLE: Boranes
Can you predict the structure of B10H14?
EXAMPLE: G14
Silylene + H2O →
EXAMPLE: G14
Silylene + H2O →
EXAMPLE: G14
Stable Germanone + H2 →
