Isosteric quality

Replacement of the carbamate group with isosteric functionalities such as an IV-methyl carbamate, urea, or amide group clearly confirmed the favorable qualities of the carbamate group [57], While the introduction of a urea group, as in case of iV-9-(tert-butylcarbamoyl)-9-desoxy-9-aminoquinine selector, instead of carbamate functionality turned out to be virtually equivalent in terms of enantiorecognition capabilities [57,58], the enantiomer separation potential was severely lost on iV-methylation of the carbamate group, like in 0-9-(N-me hy -N-tert-butylcarbamoyl)quinine [32,58], or its replacement by an amide, such as in case of Af-9-(pivaloyl)-9-desoxy-9-aminoquinine selector [57,58], For example, enantioselectivities dropped for DNB-alanine from 8.1 for the carbamate-type CSP, over 6.6 for thein-ea-type CSP, to 1.7 for the amide-type CSP, and 1.3 for the A -methyl... 

The isosteres obtained for foe sorption of these hydrocarbons were linear and all of a similar quality to foose presmted in Figure 2 for ethane sorbed in silicalite-I. 

The isosteres obtained using the isostaic systems for the sorption of CH4,1 and CO2 and their binary matures in silicalite-1 have been folly reported in previous publications [1,12]. These isosteres are linear and of a quality similar to foose shown in Fig 2. However, it has recently been realised, especially when N2 is involved but also for CH4, in the temperature range 0-70 C... 

---