Broadband-decoupled NMR

Figure 2.4. CH multiplicities of a-pinene (1) [hexadeuterioacetone, 25 C, 50 MHz], (a) h broadband decoupled NMR spectrum (b) DEPT subspectrum of CH (c) DEPT subspectrum of all C atoms which are bonded to H (CH and CH3 positive, CH2 negative) (d) an expansion of a section of (c). Signals from two quaternary C atoms, three CH units, two CH2 units and three CH3 units can be seen...

Broadband-decoupled NMR, 451 Bromine, reaction with aldehydes, 846-848... 

Figure 1.11. NMR analysis of the keto-enol tautomerism of 2,4-pentanedione [CDCI3, 50% v/v, 25 °C, 60 MHz for H, 20 MHz for C]. (a) H NMR spectrum with integrals [result keto enol = 13 87] (b) H broadband decoupled NMR spectrum (c) C NMR spectrum obtained by inverse gated H decoupling with integrals [result keto enol = 15 85 ( 1)]...

The high-resolution molecular mass of the compound gives the molecular formula which corresponds to eight double bond equivalents. The H broadband decoupled NMR spectrum shows a keto carbonyl group (185.2), two carboxy functions (176.4 and 170.4) and four further signals in the sp chemical shift range (146.8,... 

High-resolution molecular mass analysis provides the molecular formula CnH2iO of acanthifolin, which corresponds to seven double bond equivalents. The proton broadband decoupled NMR spectrum (Fig. 6a) displays all 17 carbon atoms of the molecule, including a carboxy group (5c = 170.5) and four additional C atoms in the sp range of chemical shifts (5c = 145.8, 138.1, 119.8 and 116.2), indicating two CC double bonds. Only three of all seven double bonds of the molecule are detected by NMR. To conclude, acanthifolin incorporates a tetracyclic ring system... 

Two compounds, A and B, have the same molecular formula, CeHa. Both A and B react with two molar equivalents of hydrogen in the presence of platinum to yield cyclohexane. Compound A shows three signals in its broadband decoupled NMR spectrum. Compound B shows only two NMR signals. 

K. Zangger, H. Sterk, Homonuclear broadband-decoupled NMR spectra, J. Magn. Reson. 124 (1997) 486. 

The sample prepared is not particularly pure, so instead of the 30 signals expected, 33 signals are observed in the H broadband decoupled NMR spectrum. Only by pooling information from the DEPT experiment and from the CH COSY plot can a reliable analysis be obtained, as shown in Table 51.1. Here the AB systems of the geminal CH2 protons are assigned. 

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