thus as t1 is varied the intensity of the 13c signal

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Unformatted text preview: nal will vary, depending on and JCH Now, we’ll look at the more complicated case: 6 H CHEM / BCMB 4190/6190/8189 Introductory NMR Lecture 16 -1- CHEM 4190/6190 Two-Dimensional Correlated NMR Spectroscopy 1. Two-Dimensional Heteronuclear (C,H)-Correlated NMR Spectroscopy (HETCOR or C,H-COSY): HETCOR: HETeronuclear CORrelation C,H-COSY: Correlated SpectroscopY (Observed nuclei is first) A) Pulse sequence and vector diagram -2- Lets consider a two-spin AX system with A= 1H and X = 13C ( 13CHCl3) During t1: • • ν( MH{Cα} ) = νH - 1/2*JCH; ν( MH{Cβ} ) = νH + 1/2*JCH νH = Larmor frequency in the absence of coupling (Here νH > frequency of the rotating frame) • Ignore effect of relaxation and field inhomogeneity • ϕα = 2π (νH - 1/2*JCH) t1; ϕβ = 2π (νH + 1/2*JCH) t1 Θ = ϕα - ϕβ = 2πJCH* t1 After the second 1H 90˚x' pulse: • 1H magnetization is transferred to the x'-z plane • The z-magnetization components are proportional to the population differences: N1 and N3 for MH{Cα} N2 and N4 for MH{Cβ} • In Figure 9-10 the populations of N1 and N3 are partially inverted and the population difference between N2 and N4 is modified: • In general, the population differences depend on t1, νH,...
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