ABC26IN0161 · Inorganic Spectroscopy
Subject: Inorganic Chemistry · Chapter: Inorganic Spectroscopy · Topic: Inorganic Spectroscopy – General · Exam: CSIR-NET DEC 2012 · Marks: 2 · Difficulty: Medium
Find out the number of lines in the ${}^{31}\mathrm{P}$ NMR signal for diagram 
(a)3
(b)6
(c)18
(d)90
Answer
Answer (as printed): D
Explanation
Four $\mathrm{{}^1H}$ are equivalent. Two nitrogen are equivalent. Two fluorine are equivalent. One 2H is separate.
\[ \text{Multiplicity} = \left(2\times4\times\tfrac12+1\right)\left(2\times2\times\tfrac12+1\right)\left(2\times2\times\tfrac12+1\right)\left(2\times1\times\tfrac12+1\right) = 5\times3\times3\times2 = 90 \]
($4\,{}^{1}\mathrm{H}$, $2\,{}^{15}\mathrm{N}$, $2\,\mathrm{F}$, $1\,\mathrm{H}$)