J. CHEM. RESEARCH (S), 1999 107
Experimental
Barium 2-hydroxypropyl 4-nitrophenyl phosphate (HPNPP)7 and
pyridinium bis(4-nitrophenyl) phosphate10 were prepared according
to the literature procedures.
Rate measurement.ÐTo a distilled organic solvent containing an
appropriate amount of Cu(NO3)2 Á6H2O or Zn(NO3)2 Á6H2O was
2
added 15 ꢁl of a stock solution of HPNPP [1.0Â 10 M in MeCN
2
(2% H2O) containing 18-crown-6 (1.0Â 10 M)]. For fast reactions
1
(kobs>ca. 10
s
1), the rates were followed by the stopped
¯ow method. Released 4-nitrophenol was followed with a JASCO
Ubest -560 spectrophotometer and Otsuka Electronics RA-401.
Formation of 4-nitrophenol was con®rmed by TLC analysis.
Received, 27th May 1998; Accepted, 19th October 1998
Paper E/8/03986K
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Fig. 2 The dependence of kobs on the content of H2O in MeCN.
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Rate accelerations of phosphate ester hydrolysis due
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