Polarity carbamates

The hydrogenation of C02 in the presence of amines to give dialkylformamides has been carried out directly in an IL/scC02 system. In this case, the ionic liquid was shown to play a dual role [74]. It is an effective solvent for the ruthenium phosphine catalyst and at the same time allows a distinct phase distribution of the polar carbamate intermediates and the less polar products formed during the conversion of C02. As a result, the selectivity of the reaction can be increased over conditions where scC02 is used as the sole reaction medium. 

Scheme 8.10 Formation of switchable polarity carbamate solvent.

The effects of various solid supports on the extraction recovery for a set of polar carbamates have been studied, and the results are shown in Table 10.3. It is apparent that the extraction efficiency is lower by using C-18/OH... 

Table 103. Comparison of Recoveries for Polar Carbamates with Different Extraction Sorbents...

The interaction energy difference between the enantiomers was clearly reeog-nized only when the enantiomers were generated in a chiral groove of 6f and 6p. This result indicates that the polar carbamate groups of these phenylcarbamate derivatives may be the most important chiral recognition site for polar racemates. 

The highly polar carbamate pesticides cannot always be analysed by GC-MS (Figures 3.95-3.97). The low thermal stability leads to decomposition even in the injector. Substances with definite aromatic character, however, form stable intense molecular ions. 

As far as the cellulose triphenylcarbamate (CTPC) or amylose triphenylcar-bamate (ATPC) is considered, the important sites are the polar carbamate groups. CTPC exhibits a left-handed threefold helix and glucose residues are regularly... 

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