Answer to Question #122557 in Inorganic Chemistry for Mariah

Question

(a) In what ways are 31P NMR spectroscopic techniques similar and different to 1H/13C
variants?
(b) What do you understand to be the benefit of isotopic enrichment in NMR?

Answer 1

a) The $31$ Phosphorus NMR experiment is much less sensitive than proton  but more sensitive than Carbon. $31$ Phosphorus is a medium sensitivity nucleus that yields sharp lines and has a wide chemical shift range. It is usually acquired with decoupling which means that spin-spin couplings are seldom observed. This greatly simplifies the spectrum and makes it less crowded. Where there are one-bond $31$ P-H couplings present then the decoupling power needs to be at lest twice that needed for $13$ C because of the large coupling constant.

b) Nuclear magnetic resonance spectroscopy (NMR) is a powerful tool which takes advantage of the magnetic properties of certain nuclei. The basic principle behind NMR is that some nuclei exist in specific nuclear spin states when exposed to an external magnetic field. NMR observes transitions between these spin states that are specific to particular nuclei as well as that nuclei's chemical environment. The concept however, applies to nuclei whose spin$1$ ,is not equal to , so the nuclei $1=0$ are invisible to the NMR spectroscopy. NMR is widely used to identify molecular structures , monitor reactions , study metabolism in cells , in biochemistry, medicine , physics and almost every branch of science.