Zur praxis von 13CMR-linienintensitätsmessungen

Carbon-13 nuclear magnetic resonance substituent-induced shieldings and conformational equilibriums in cyclohexanes

“…Under proton noise decoupling conditions, differential nuclear Overhauser effects will give rise to deviations of signal areas mainly if, in the case of nonquaternary carbon atoms, the distance between carbon and directly bonded hydrogen does not remain constant.46 That these differences usually are negligible, if one compares exchanging stereoisomeric carbon atoms, is shown by the consistency of signal area ratios in to-pomers7b and in epimeric mixtures. 47 Here we find the accuracy of quantitative 13C spectroscopy surpassing that of 1H NMR methods. Small but consistent signal area deviations are found only for carbon atoms Ca, which alternatively bear equatorial or axial substituents.7b'44a>47 Our observation of larger Ca peaks, in most cases by 5%, in le and related compounds supports the interesting suggestion of elongated equatorial as compared to axial C-H bonds in cyclohexanes.…”

Nuclear magnetic resonance spectroscopy

“…group as a function of the dielectric constant of the solvent (817), lithioisobutyrophenone and its complexes with lithium chloride and bromide (818), alicyclic methyl esters (819) , oligo(oxy-2,2-dimethylethylenecarbonyl) compounds (820) , alkyl substituted furans (821), benzofurans (822), 2-substituted furans, thiophenes, and tellurophenes (823), methyl-substituted 1,3-oxothianes (824), 2-amino-4phenylbenzothiazoles (825), barbiturates (826), coumarin and its methyl derivatives (827), and 5-alkyl-5-(l-methylbutyl)barbituric acids (828) have been described. The NMR determination of electronic densities in quinoxalines and quinolines (829), and symmetrical naphthyridines (830), additivity effects on the H-H coupling constants of disubstituted pyridines (831), 13C-F coupling constants of fluoropyridines (832), medium effects on the 19F NMR of fluoropyridines (833), 13C NMR line intensity measurements for quinoline and other compounds (834), cis and trans isomers of 2-chloroand 2-phenyl-5-methyl-1,3,2-oxathiaphospholane (835), sodium (p-methoxyphenyl)methylphosphinodithioate dihydrate (836), thioand di-thiooxamides (837), derivatives of dithiocarbazic acids (838), quaternary ammonium salts (839), TV-substituted methylamines (840), 2-, 3-, and 4-substituted TV-methylpyridinium salts (841), n-alkyl ammonium salts (842), simple quaternary salts of 1 -methylpyrazole (843), complexes of nitrophenols with dialkylamines (844), nitrotoluidines (845), acyclic aliphatic amines (846), 5-substituted 10,11dihydrobenz[b,f]azepines (847), polytertiary amine chelated alkali metal compounds (848), acrylic amines (849), primary amines (850), pyrrole (851), pyrrole derivatives (852) and tetrapyrroles (853), 8-hydroxyquinoline (854) and its derivatives (855), protonation of L-cysteine (856), protected amino acids (857), determination of glutethimide (858), diazoalkanes (859), substituted pyrazoles (860), 1,4-oxathiane derivatives (861), l-alkyl-2(lH)-pyridinone derivatives (862), purine derivatives…”

Synthesis and reactions of an open‐chain bis‐reissert salt analog

“…A %nmr of 4 indicated separate signals for the carbons C-2, C-4 and C-5 (the C-3 signals were quite broadened) with almost equal signal areas thus representing a 1:l meso-dl mixture [14]. Treatment of 5 with sodium carbonateldeuterium oxide gave the deuteroanalog 4c as a meso-dl mixture (1:l) as ascertained by the signal areas of C-2, C-4 and C-5 carbons in the Y -n m r [14]. All of these data are in agreement with the structure 5a as representing the major tautomeric form of 5.…”