R-Co compounds

In the case of hard magnetic materials it is usually tried to increase B, to the same value as 4irAfs. This is however only possible if a strongly anisotropic material is either present in single crystal form or if at least all magnetic easy axes of all crystallites are magnetically aligned parallel. This latter condition is fulfilled in many R-Co compounds. 

Fig. 4. Dependencies of d In 7) /d In V on Tq calculated for R-Fe and R-Co compounds by using eq. (29) (dot-dashed curve), eq. (44) (solid curve), and eq. (45) (dashed curve). Experimental values are shown as solid circles for R-Co and as open circles for R-Fe (Inoue and Shimizu 1984).

From the band model point of view one can expect an essential variation of Oq under pressure in ferromagnets where 3d subbands of opposite spin directions are not full (Buschow et al. 1977). Such a situation is realized in R-Fe compounds where large values of 9 In o /dP are observed experimentally for YgFe23, YFe3, YFe2 and CeFe2 with exclusion of Y2Fei7 (see table 8). On the contrary in R-Co compounds the 3d band of one spin direction is full and this should correspond to the small variation of Oq. Unfortunately, experimental data on 9 In Oo/9P in R-Co compounds are not available. 

A peculiar behaviour is shown by the CaCuj type R-Co compounds. As one proceeds through the rare earth series from La to Lu the stoichiometry changes from 1 5 to approximately 1 6. All these CaCu5 type compounds decompose at low temperatures into R2Co,7 and R2C07 (Buschow, 1974 den Breeder and Buschow, 1980). 

Ester groups in R —CO—OR compounds are named (1) by the prefix alkoxycarbonyl- or aryloxycarbonyl- for —CO—OR when the radical R contains a substituent with priority for citation as principal group or (2) by the prefix acyloxy- for R —CO—O— when the radical R contains a substituent with priority for citation as principal group. Examples are... 

Phthaleins. Dyes of this class are usually considered to be triaryhnethane derivatives. Phenolphthalein [77-09-8] (23, R = CO) and phenol red [143-74-8] (23, R = SO2) are used extensively as indicators in colorimetric and titrimetric determinations (see Hydrogen-ION activity). These compounds are prepared by the condensation of phenol with phthaUc anhydride or i9-sulfoben2oic anhydride, respectively, in the presence of a dehydrating agent. 

In recent years the number of relatively simple sulfonyl molecules for which geometry has been determined in the vapor phase has increased considerably. The additional data are listed in Table 3. At this point there are a total of 40 geometries for sulfonyl compounds that have been determined in the vapour phase all of them are indicated in the r sin a versus r cos plot in Figure 19. While this number corresponds to a much larger sample of data than that considered previously, unfortunately the accuracy and the experimental sources are much more variable than for the smaller sample therefore, no rigorous conclusions should be drawn on the basis of these data. It is remarkable, however, that the mean O O nonbonded distance of the 40 geometries is the same, 2.484 A, as in the smaller... 

Kelvin scale A fundamental scale of temperature on which the triple point of water lies at 273.16 K and the lowest attainable temperature is at 0. The unit on the Kelvin scale is the kelvin, K. ketone An organic compound containing a carbonyl group between two carbon atoms, having the form R—CO R. Example CH3—CO—CH2CH , butanone. kilogram (kg) The SI unit of mass. See also Appendix IB. 

When applied to ketones, this is called Norrish Type / cleavage or often just Type I cleavage. In a secondary process, the acyl radical R —CO can then lose CO to give R radicals. Another example of a category 1 process is cleavage of CI2 to give two Cl atoms. Other bonds that are easily cleaved by photolysis are the 0—0 bonds of peroxy compounds and the C—N bonds of aliphatic azo compounds R—N=N—R. The latter is an important source of radicals R , since the other product is the very stable N2. 

Oxo-2,5-cyclohexadienylidene [83] was generated in solid argon at 9 K by irradiation of diazo compound [84] with visible light (A>495 nm) (Sander et al., 1988 Bucher and Sander, 1992 Bucher et al., 1992). The IR, UV, and esr spectra of [83] were in accord with a structure having a triplet state with one delocalized electron. In the IR spectrum of the carbene [83] the r (CO) mode was found at 1496 cm which indicates a bond order of the C—O bond considerably less than 2. The low-temperature reaction of carbene [83] with CO generated the keto-ketene [85]. Irradiation (A = 543 10 nm) of [83] led to its transformation into a very labile species, presumed to be [86], which rearranged back to [83] not only under UV or... 

Although polymers in-service are required to be resistant toward hydrolysis and solar degradation, for polymer deformulation purposes hydrolysis is an asset. Highly crystalline materials such as compounded polyamides are difficult to extract. For such materials hydrolysis or other forms of chemolysis render additives accessible for analysis. Polymers, which may profitably be depolymerised into their monomers by hydrolysis include PET, PBT, PC, PU, PES, POM, PA and others. Hydrolysis occurs when moisture causes chain scissions to occur within the molecule. In polyesters, chain scissions take place at the ester linkages (R-CO-O-R ), which causes a reduction in molecular weight as well as in mechanical properties. Polyesters show their susceptibility to hydrolysis with dramatic shifts in molecular weight distribution. Apart from access to the additives fraction, hydrolysis also facilitates molecular characterisation of the polymer. In this context, it is noticed that condensation polymers (polyesters, -amides, -ethers, -carbonates, -urethanes) have also been studied much... 

Dioxygen and its ions can bind in mononuclear and dinuclear structures in a number of ways,962 as illustrated in Scheme 1. The typical reaction of dioxygen with Co compounds involves a number of these binding forms, outlined in Scheme 2. Mononuclear Co111—peroxo complexes are relatively rare, but yellow trigonal bipyramidal complexes [Co(02)L2]+ (L = chelating phosphines dppe or dppp) have been characterized structurally where the 022 is bonded to the Co in the side-on r]2 form (Co—O 1.858(7) 1.881(4) A), with O—O stretching frequencies ( 870 cm-1) consistent with Coin-peroxo speciation.963... 

The rate constants for the 02 reaction do not vary significantly with different ligands (X = F, Cl, Br). The reaction of trans-[ r(CO)(CH3CN)(PPh3)2]1 with 102 is slightly slower than for the halide analogues.621 The peroxo compounds do not react with alkenes. 

Experiments show that substances with the formula R—CO— CHOH—R react with /3-dicarbonyl compounds to give furan derivatives having the following general formula. It is noteworthy that this reaction... 

We have delineated viable coordinated ligand reactions and their attendant intermediates for the stoichiometric conversion of CO ligands selectively to the C2 organics ethane, ethylene, methyl (or ethyl) acetate, and acetaldehyde. We now outline results from three lines of research (1) T -Alkoxymethyl iron complexes CpFe(C0)2CH20R (2) are available by reducing coordinated CO on CpFe(C0)3+ (1) [Cp = r -CsHs]. Compounds 2 then form t -alkoxyacetyl complexes via migratory-insertion (i,e. CO... 

The results of ion-pairing separation of this compound according to the method of Conboy et al. [36] with MS detection in the ESI—LC— MS(+) mode was not promising. Even at a concentration of 50 mg L 1 of this esterquat in the standard solution, the S/N ratio was poor [39]. The base peak was the ion at m/z 428, representative of the fragment ions (R(CO)OCH2CH2)-N (CH3)(CH2CH2OH)2 with R = C17H33. 

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