Nuclear magnetic resonance alkyl chains

In order to explain the spectroscopic properties, particularly nuclear magnetic resonance, of the complexes (CO)5Mn CH2 CH2 CHR Mn(CO)5 (R = H or Me), King (55) postulated an interaction between the hydrogen atoms of the alkyl chain and the manganese atoms. In the... 

Stronger chemical evidence for the presence of a dithiolene in molybdopterin was obtained when the mild alkylation reagent iodoacetamide effectively trapped the dithiolene (65). This reaction yielded a derivative whose characterization by FAB mass spectrometry and nuclear magnetic resonance (NMR) was consistent with the structure shown in Fig. 5. The method appeared to leave the side chain intact and preserved the pterin oxidation state. From this experiment the view persisted that molybdopterin is a disubstituted dithiolene bearing a reduced pterin and a short chain terminated with a phosphate. 

As indicated in Section 11,4 (p. 64), direct treatment of alkyl halides with sodium cobalt tetracarbonyl, carbon monoxide, and methanol at elevated temperatures and pressures yields esters. Surprisingly, application of this reaction at 60° (using methanol instead of ether) to methyl tri-0-acetyl-2-deoxy-2-iodo-/3-D-glucopyranoside gave, almost exclusively, the elimination product (88) (in deacetylated form) and a compound presumed to be (on the basis of nuclear magnetic resonance evidence only) the branched-chain ester (87) in less than 0.5 % yield. It is thought that, in the presence of methanol, the sodium cobalt tetracarbonyl dissociates to yield sodium methoxide, and that this causes deacetylation of the substrate. 

Bidentates of di(alkylsalicoyl) (DAS) and ethylenediaminetetraacetic acid, with different alkyl chain lengths in the DAS were prepared and conjugated with polyethylene glycol. The materials were structurally characterised using nuclear magnetic resonance spectroscopy and were submitted for evaluation as oral drug delivery systems in vitro and in vivo. 14 refs. 

T is therefore attributed to the melting of the paraffinic phase composed of alkyl side chains. The slight contraction of the intersheet distance observed for this transition is consistent with a small deviation of the C-C torsion angles from the -trans conformation. Therefore, the phase appearing above T is regarded as a structure with the side chains in a conformation not very different from that present at low temperatures. Solid-state nuclear magnetic resonance (NMR)... 

Partially or completely deuterated alkyl chains are prepared mainly for experiments such as neutron scattering or nuclear magnetic resonance (NMR). The transition temperatures are usually the same as or very similar to those of the analogous alkyl compounds [121] however, exceptionally, there can be differences of about 10 K [96]. 

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