Awesome Chemistry Experiments For 33100-27-5

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In an article, published in an article, once mentioned the application of 33100-27-5, Name is 1,4,7,10,13-Pentaoxacyclopentadecane,molecular formula is C10H20O5, is a conventional compound. this article was the specific content is as follows.Application In Synthesis of 1,4,7,10,13-Pentaoxacyclopentadecane

Steric and stereoelectronic effects in aza crown ether complexes

Stability constants and enthalpy changes determined by calorimetric titrations and supported by selected NMR titrations are reported for the complexation of sodium and potassium cations with 18 different crown ethers containing nitrogen atoms with different number, location and substitution pattern. The data, measured in methanol mostly with potassium salts, are compared to literature data; they show striking differences between all-oxygen analogs and the macrocycles with NH groups. In contrast, affinities with aza crown ethers bearing alkyl groups at the nitrogen as well as with the cryptand [2.2.2] come closer to the complexation free energies predicted from the number and electron donating capacity of the ligand heteroatoms. This is rationalised on the basis of molecular mechanics calculations, showing that a NH-containing crown predominates in conformations with axial N lone pairs, due to their repulsive electrostatic interactions with the ring oxygen atoms. Replacement of the hydrogen by alkyl groups forces the lone pairs to an equatorial position, thus enabling better complex formation, as borne out by experiment. In line with these arguments the IgK differences are with some exceptions more due to DeltaH than to TDeltaS differences. The calorimetric data show linear isoequilibrium correlations between TDeltaS and DeltaH, with slopes between those observed with other crown ether and cryptand complexes. Preliminary investigations of some synthetic macrocyclic amide precursors yield appreciable complexation only, if the two carbonyl oxygens can come in close contact with the guest cation. Computer aided molecular modelling shows that this is possible in a small 15C5-derivative, in which the polyethylenglycol cycle only serves as ring template without binding contributions from the ether oxygen atoms.

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Reference£º
Chiral Catalysts,
Chiral catalysts – SlideShare