The nuclear magnetic resonance NMR spectrum

The nuclear magnetic resonance (NMR) spectrum of chrom-3-ene (1) has been measured13 and the sign of coupling constants between protons on the hetero ring obtained from a study of double quantum transitions.13 An inter-ring coupling (J4 8) has been detected.14-16 In... 

A striking feature in the nuclear magnetic resonance (NMR) spectrum of compound 17 was the complexity of the... 

The nuclear magnetic resonance (NMR) spectrum (Fig. 2) was obtained by preparing a saturated solution of meperidine hydrochloride, U.S.P. (Wyeth Lot No. F-665901) in deutero chloroform containing tetramethylsilane as internal reference. The only exchangeable proton is the hydrogen associated with HC1. The NMR proton spectral assignments are given in Table II. 

The spectral data seems to support the suggestion that B has two carbon-carbon double bonds. The carbon-carbon triple bond would resonate at about 2.5 to 3.0 parts per million. The lowest absorbance in the nuclear magnetic resonance (nmr) spectrum of structure B is 3.84 parts per million. The carbon-carbon double bond would resonate at about 5.5 to 6.5 parts per million. There is an absorbance at 6.55 in the nmr spectrum of B. This corresponds to the two carbon-carbon double bonds absorbance. Hence, structure B has two carbon-carbon double bonds. The reason why a... 

Here, these alkaloids will be described in this chapter as alkaloids based on a porphine skeleton. Their biosynthesis is completely different from that of prodigiosin described in the chapter on alkaloids derived from proline (Chapter 5). Total synthesis of chlorophyll a was achieved [2,3], and the assignment of all resonances in the nuclear magnetic resonance (NMR) spectrum of chlorophyll b has been accomplished [4]. Also the biosynthesis and chemistry of the chlorophylls have been reviewed [5—8]. 

The nuclear magnetic resonance (NMR) spectrum may provide information on the types of fundamental groups present in a molecule and the stereochemical relationships between neighbouring groups. The resonance of H, C, and nuclei in a magnetic field have all found considerable use in phosphorus chemistry, and this has been aided considerably by the advent of Fourier transform techniques [65,73,79,84]. 

The donor number (D.N.) and acceptor number (A.N.) are important parameters describing the polarity of a solvent in terms of ifs solvahon energy for ions. For example, in Equahon 9.1, fhe D.N. is fhe enfhalpy change of solvent D in 1,2-dichloroethane (-AH kcal/mol). The A.N. is the chemical shift in the nuclear magnetic resonance (NMR) spectrum of EfgPO in fhe solvenf D. It is assumed that the D.N. of hexane is 0 and 100 for EfgPO SbCls in 1,2-dichloroethane. The D.N. reflects the nucleophilic property of a solvenf (basicify), and fhe A.N. reflects the electrophilic property of a solvenf (acidify). 

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