Complexation studies of crown ethers with alkali metal cations in methanol

Simple item page
dc.contributor.authorKeng Yoon, Yeong
dc.date.accessioned2014-11-14T07:50:59Z
dc.date.available2014-11-14T07:50:59Z
dc.date.issued2004
dc.descriptionMasteren_US
dc.description.abstractThe alkylation reaction between dibenzo-15-crown-5 (DB15C5) and t-butyl alcohol in trifluoroacetic acid yielded 2,3,8,9-(4’,4”-di-tert-butyl)-dibenzo-1,4,7,10,13- pentaoxacyclopentadeca-2,8-diene (t2-DB15C5). The f2-DB18C6 (mixture of 4’,4”-diformyl benzo18-crown-6 and 4’,5”-di-formyl benzo18-crown-6) was synthesized from dibenzo-18-crown-6 (DB18C6) via a facile formylation process employing hexamethylenetetramine and trifluoroacetic acid. Both compounds were obtained in good yield ( 80% for t2-DB15C5 and 55-65% for f2-DB18C6). The structures were identified using elemental analysis, IR, MS, 1H NMR and 13C NMR spectroscopy. The complexation of DB15C5 with alkali metal cations as well as Sm3+, Nd3+ and Pr3+ in methanol were investigated using 1H NMR spectroscopy and UV spectroscopy. A 1:1 stoichiometry complex was observed with Li+ and Na+ as well as Sm3+, Nd3+ and Pr3+ while K+ gave 2:1 (sandwich) complex. Both 1:1 and 2:1 (sandwich) complexes were observed Cs+. The type of complex formed by DB15C5-Rb+ depends on the ratio of host to guest used. At 1:1 host to guest ratio used, DB15C5-Rb+ showed a mixture of 1:1 and 2:1 sandwich complexes. Nevertheless, when we have excess of host DB15C5-Rb+ form 2:1 sandwich complex. The complexation of t2-DB15C5 with alkali metal cations was also carried out in methanol. A 1:1 stoichiometry complex was observed with Li+ and Na+ while K+, Rb+ and Cs+ all gave 2:1 (sandwich) complex. For 1:1 stoichiometry complexes, the t-butyl substituent groups on the benzene ring of t2-DB15C5 increase the stability of the complex by one fold compared to DB15C5. The association constants for 1:1 stoichiometry complexes were found in the order of Li+  Na+ for DB15C5 and t2- DB15C5. The complexation of DB18C6 and f2-DB18C6 with alkali metal cations were carried out in the methanol-chloroform (8:2 v/v). DB18C6 gave 1:1 stoichiometry complexes with Li+, Na+ and K+ while Cs+ gave both 1:1 and 2:1 (sandwich) complexes. The type of complex formed by DB15C5-Rb+ depends on the ratio of host to guest used. DB18C6- Rb+ gave 1:1 complex when we have excess guest. However, when we have excess host, the majority of complex formed was 2:1 sandwich complex. The association constants for 1:1 stoichiometry complexes were found in the order of Na+  K+  Li+ for DB18C6. For f2-DB18C6, besides the ether oxygens, the carbonyl oxygens were also involved in the complexation with alkali metal cations.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/501
dc.language.isoenen_US
dc.subjectChemical scienceen_US
dc.subjectCrown ethersen_US
dc.subjectMethanolen_US
dc.titleComplexation studies of crown ethers with alkali metal cations in methanolen_US
dc.typeThesisen_US
Files
License bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
license.txt
Size:
1.71 KB
Format:
Item-specific license agreed upon to submission
Description:
Download
Collections
Pusat Pengajian Sains Kajihayat - Tesis