Electric Literature of 33100-27-5. Let¡¯s face it, organic chemistry can seem difficult to learn. Especially from a beginner¡¯s point of view. Like 33100-27-5, Name is 1,4,7,10,13-Pentaoxacyclopentadecane. In a document type is Article, introducing its new discovery.
Cavity-size-dependent dissociation of crown ether/ammonium ion complexes in the gas phase
Ion complexes of crown ethers and amine substrates were generated by liquid secondary ion mass spectrometry (LSIMS). The ammonium ions were produced from the precursors: ammonium chloride, methylammonium and hydrazinium hydrochlorides, methylhydrazine sulfate, and tosylhydrazine. The effective hydrogen bonds between the ammonium ions and multi-oxygen receptors are the predominant binding interactions in the complex formation. Results of collision-induced dissociation (CID) of the ion complexes at 7 and 0.4 keV show two strikingly different types of fragmentation pathways. At the lower collision energy, the dominant dissociation pathways involve decomplexation in conjunction with losses of ethylene oxide units from the resulting protonated ether molecules, which are the fragmentation processes previously observed for dissociation of protonated crown ethers. In addition, metastable ions corresponding to decomplexation of neutral amines from the polyether/ammonium ion complexes by intramolecular proton transfer are also observed. Higher collision energy activation and dissociation of the ion complexes proceed by intramolecular ring-opening reactions which result in odd-electron, acyclic product ion structures. These ring-opening reactions are significantly favored over the simple eliminations of ethylene oxide units as the cavity sizes of the crown ethers increase and the strengths of hydrogen-bonding interactions increase. Hydrazinium and methylhydrazinium ion complexes dissociate via macrocyclic ring-opening pathways that result in the loss of hydroxymethylene radical. This ring-opening reaction is the dominant dissociation pathway when the host cavity is large enough to encapsulate the hydrazinium ion, such as for 18-crown-6 and 21-crown-7. In contrast, ion complexes of crown ethers with tosylhydrazines dissociate by covalent bond cleavage of the nitrogen-sulfur bond of the guest substrate. These results suggest that the association energy for the multiple hydrogen-bonding interactions of the crown ether/ammonium ion complex is on the same order of the covalent macrocyclic or nitrogen-sulfur bonds.
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Chiral Catalysts,
Chiral catalysts – SlideShare