Isomer Co

Neomethymycin (12, R = H, R = OH), an isomer co-produced with methymycin, is the product of hydroxylation at C-12 rather than C-10 of the lactone (34,35). The corresponding aglycone, neomethynoHde (13, R = H, R = OH), was isolated with methynolide from broths of S. vene elae (36). The stereochemistry of 12(R)- for neomethynoHde was estabHshed by total synthesis (37). YC-17 (12, R = R = H), also found in broths of S. vene elae is a possible precursor of methymycin and neomethymycin. The hydroxyl groups at C-12 and C-10 are probably added as late steps in the biosynthesis (38). 

Reiter et al. (87T2497) could also differentiate between oxo-TPs and [4,3-a] isomers. (CO in TPs absorbs at 10-20 cm-1 higher wave numbers.) However, the influence of other substituents is more remarkable and consequently the IR spectra cannot be used in general for elucidation of the structure of the four isomeric types. 

When M0O2- coordinates to a metal ion, as in [Co(NH3)5Mo04]Cl or [Co(NH3)4Mo04]N03, the IR and Raman spectra of the M0O4- grouping are perturbed.22 An instructive example considers the coordination isomers [Co(NH3)5C1]Mo04 and [Co(NH3)sMo04]C1.22... 

The ionization isomers [Co NHj)5Br]S04 and [CofNHj SOJBr dissolve in water to yield different ions and thus react differently to various reagents ... 

The synthesis of cobalt meso-diphenyl corrolates has also been reported [31]. The synthetic procedure involves the acidic condensation of 3,4-dimethyl-2-(a-hydroxybenzyl)pyrrole-5-carboxylic acid with 3,3, 4,4 -tetramethyl dipyrro-methane, followed by reaction with cobalt salts. The reaction afforded a mixture of two isomers Co(5,15-OMDPC)PPh3 and Co(5,10-OMDPC)PPh3. The formation of this latter isomer has been explained by the high tendency of self condensation of the starting pyrrole under the reaction conditions, 2-(a-hydroxybenzyl)meso-phenyl dipyrromethane can be formed. This species would afford the Co(5,10-OMDPC)PPh3 by further condensation with the dipyrromethane unit present in excess in the reaction mixture. 

Co(ONSSNO)jI (two isomers) CoS 224-5 CoO 189-190 CoN 194-6 Brown isomer (NSSN planar) green (two forms NSSN bent, planar) 5... 

This arises when the counterion in a complex salt is a proligand and can, in principle, displace a ligand which can then become the counterion. An example is provided by the ionization isomers [Co(NH3)5SOJBr and [Co(NH3)5Br](S04). 

The reason for this difference is not yet obvious, nor is it clear whether this is a general phenomenon. In fact, an opposite trend was reported for the styrene-trimethylamine system [27], In any case, the difference in ionization efficiency may become another tool for studying gas-phase systems. In cases where several R-isomers co-exist in the jet, some differences were recorded in their photophysical behavior. The change in the rate of R E isomerization was found to depend on the internal energy in a different way. However, the differences were in general small. 

Other Nitrogen Donors. The trigonal-bipyramidal [Ru(CO)2(NNPh)(PPh3)2]PF6 has been prepared from Ru(CO)3(PPh3)2 and PhN two isomers co-exist in solution. Addition of halide ions give rise to an octahedral complex with a doubly bent RuN2Ph moiety. ... 

Partial Resolution of Optical Isomers. Co(admh)(acac)2 was resolved partially on a previously described 230 x 3.9 cm o.d. column of D-(+)-lactose (10). In two separate chromatograms, 130 mg of sample dissolved in 1.5 ml of benzene was placed on the column and eluted with l.-l benzene-hexane. The entire eluted solution was collected in two parts. The first fractions from each chromatogram were combined and evaporated to dryness. The enantiomer in excess was then concentrated by extracting the residue with 1 ml of hexane. 

In some cases a nucleus may exist for some time in one or more excited states and it is differentiated on this basis. Such nuclei that necessarily have the same atomic number and mass number are called isomers. "Co and Co are isomers the " Co nuclide exists in a high energy (excited) state and decays spontaneously by emission of a y-ray with a half-life of 10.5 min to the lowest aiergy, ground state, designated by Co. 

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