Amidines. Part 31. pK_avalues of N¹,N¹-dialkyl-N²-phenylformamidines in water–ethanol solutions

Effects of mixed CH3CN(SINGLEBOND)H2O solvents on rate of intramolecular general base-catalyzed cleavage of ionized phenyl salicylate in the presence of 3-aminopropan-1-ol, 1,2-diaminoethane, and glycine

“…The values of several cationic amines are larger by pK a several pK units in pure CH 3 CN solvent compared to those in pure water solvent [22]. Similarly, values pK a of several amidines in mixed aqueous-ethanol show that at 95.6%, at 80% at pK w/w Ͼ pK w/w Ͻ pK a a a 50% at 30%, w/w, ethanol [23]. w/w Ͻ pK a I would like to thank the University of Malaya for financial support through F Vote (F408/96) and A. George for assisting in the determination of of cationic amine.…”

Effects of CH3OH-H2O and CH3OH solvents on rate of reaction of phthalimide with piperidine

“…The mixed aqueous-organic solvents (both protic and aprotic organic cosolvents) should have little effect on the ionization constants (K a ) of isoelectric ionization reactions (i.e., reactions of the type: BH ϩ L B ϩ H ϩ ). Similarly, pK a values of several amidines in mixed aqueous-ethanol showed that pK a at 95.6% w/w Ͼ pK a at 80% w/w Ͻ pK a at 50% w/w Ͻ pK a at 30% w/w ethanol [68]. The effects of mixed aqueous-organic solvents on pK a of conjugate acids of several amines have been reported where the increase in the contents of organic cosolvents increases the K a to the certain range (ϳ50 -80% v/v) of the contents of organic cosolvents [14,22,65,66].…”

Basicity of some aliphatic amines in mixed H2O?CH3CN solvents

“…Values of [3]. The values for N 1 ,N 1dimethyl-N 2 -phenylformadines showed a minimum at 50% w/w ethanol in water -ethanol binary solvents [4]. The values of pK a ms for phenol, obtained within the acetonitrile content range 2 -50% v/v, fit to an empirical equation, Eq.…”

“…The pK a 's of conjugate acids of pyridine and 1,1,3,3-tetramethylguanidine derivatives have been determined in pure acetonitrile and water solvents [3]. The ionization constants of conjugate acids of three series of amidine derivatives have been determined in mixed ethanol -water solvents and these determined pK a correlated with Hammett substituent constants () [4]. The pK a values of several primary, secondary, and tertiary amines have been measured in aqueous ethanol with an aim to use these pK a values in discussing the kinetic data on nucleophilic substitution or addition -elimination reactions involving these amines and solvents [5 -7].…”