Effects of Li+ and K+ ions on the rate of intramolecular general base-catalysed methanolysis of ionized phenyl salicylate in the absence and presence of cationic micelles in mixed H2O-CH3CN solvents

✍ Scribed by M. Niyaz Khan; Zainudin Arifin

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 483 KB
• Volume: 9
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199605)9:5<301::aid-poc784>3.0.co;2-7

✦ Synopsis

Pseudo first-order rate constants (kohl) for methanolysis of ionized phenyl salicylate (PS-) show a decrease of 3-5-fold with increase in CH,CN content from 2 to 60 or 70% (v/v) in mixed aqueous solvents containing 0.01 mol dm-3 LiOH and a constant content of CH30H. At 0.01 moldm-' KOH, the rate constants, kobal, reveal a decrease of 15-20% and an increase of 70-130% with increase in the CH,CN content from 2 to 30% (v/v) and from 30 to 60 or 70% (v/v) respectively. The values of AH$ and ASS are not significantly affected by the presence of 2,30 and 70% (v/v), CHJN in mixed aqueous solvents containing 10% (v/v) CH30H and 0.01 mol dm-' KOH. The presence of 0.01 mol dm-' LiOH causes the increases in AH$ and AS$ of 3.82 kcal mot-' and 10.3 cal K-' mol-', respectively, with increase in CH,CN content from 2 to 60% (v/v) in mixed aqueous solvents containing 20% (v/v) CH30H. An increase in the total concentration of cetyltrimethylammonium bromide ([CTABr],) from 0.0 to 0.01 moldm-' decreases kohl by 3.6-and 4.0-fold in the presence of 0-01 m ~l d m -~ Li' and K ' ion, respectively, in mixed aqueous solvents containing 2% (v/v) CH3CN and 10% (v/v) CH,OH. ' [LiOH] =0.01 moldm-'. * [KOH] = 0.01 mol dm-'. 'Calculated from equation (2) using cmc values obtained by iterative technique as described in the text. sValues in parentheses were obtained using Broxton er al.'s technique."' hObtained from equation (2) using cmc values determined by Broxton er d ' s techniq~e.'~' moldm-'. [CH,OH] = 10% (v/v), [CH'CN] = 2% (v/v), [H,O] = 88% (v/v), 35 "C Error limits are standard deviations.