Studies of Configuration

The studies of configuration showed that telomers were formed predominantly as E-form. The data of relative kinetics show that the partial chain transfer constants for telomer radicals are close to one and do not change virtually as the length of the radical chain grows. 

Determinations of projected atom positions are much more difficult for atoms in the Interior of the particle if the atoms are not conveniently aligned in straight rows in the direction of the incident electron beam. For the immediate future only the most favorable cases will be studied but with the application of anticipated Improvements of resolution to the l.sX level or better and the means for more accurate and automated measurement of the necessary Instrumental parameters, the detailed study of configurations of atoms in small particles should become generally feasible. 

When ambiguity exists, the study of model solutes of known configuration becomes particularly important before a solvation model for the particular solute type can be assigned. Lactones, for example, possess two oxygen atoms whose relative basicity is not immediately apparent. A study of configurationally known examples (33) indicated the primary basic site to be the carbonyl oxygen. The lactone model, illustrated by solvates 11 for an a-substituted butyrolactone... 

Q. Mao, G. Sun, S. Wang, et al. Gomparative studies of configurations and preparation methods for direct methanol fuel cell electrodes. Electrochimica Acta 52... 

Configurationally stable is a term which has meaning only when it is associated with a temperature and a timescale. The three methods allow us to define three timescales on which configurational inversion may take place. Firstly, the NMR timescale, which is dependent on peak separation, but typically is sensitive to rates of the order of 100-10 s-1.8 The temperature limits on dynamic NMR experiments mean that studies of configurational stability on the NMR timescale are applicable only to compounds which racemise with within seconds at room temperature. 

Epimerhation of hydroxyl groups. Epimerization of hydroxyl groups is often effected by S 2 displacement of the tosylates of the alcohol with tetraethylammonium acetate (1, 1136-11.37 2. 397) or with tetra-n-butylammonium acetate (3, 277). In connection with a study of configuration and biological activity in the prostaglandins, Corey and Terashima examined the reaction of the tosylatc of the model (-t)-hydroxy-laclone (1) with 5.0 eq. of tetra-n-butylammonium acetate in acetone at 25" for 2 hr. 

Studies of Configuration.— The separation of diastereomeric bisphosphonium salts was monitored by n.m.r. N.m.r. was also able to detect <3% of a minor isomer of the diphosphine palladium complex (26). Mercury-199 n.m.r. spectra showed extra splitting due to bound diastereomeric phosphorus groups. The threo- and erythro- forms of the phosphine (27) gave well separated signals (8p—17 and —27). Diastereomeric anisochronocity of various -aminophos-phonates (28) has also been reported. ... 

The study of configurational stability is of prime importance since, for example, it allows us to know the timescale during which a reaction must occur in order for the configuration of a chiral reactant to be maintained. Taking, for example, the coordination compound [Cr° C204)3]K3 (2.10) K3, obtained as an enantiomer with a negative sense of rotation ([a] p = —1800 (c = 0.02, the value of the rotation diminishes... 

Two groups report n.m.r. studies of configurational rearrangements of cis-and rranj-[Ti (LL)2X2]. " When LL=2,4-dimethylpentane-2,4-diolate or... 

Because the cross peaks in NOESY spectra arise from spatial interactions, this type of spectroscopy is particnlarly well suited to the study of configurations and conformations of molecules. The example of acetanilide demonstrates the capabilities of the NOESY experiment. The structural formula is shown, with the proton NMR chemical shifts of the relevant protons indicated. 

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