eng Ansari Education and Research Society Journal of Ultra Scientist of Physical Sciences August 2008 20 2 397 404 jusps-B 1318 article S. Prabha 1 V. Singh Sahni 2 School of Studies in Chemistry, Jiwaji University Gwalior (INDIA) Prof. Chemistry Govt. K.R.G., PG Autonomous College, Gwalior (INDIA) <p style="text-align: justify;">The diester as its monochloridate (C-N-P-linkage) is functionally modified, by the introduction of a p-methoxy substituent in the aryl matrix. The hydrolysis proceeds in the pH region 1.24-10.00 in 20% acetic acid (v/v) at 40^oC. First order rate constants have been estimated in the entire range of study using Allen&#39;s modified method of colorimetric measurement. Initial increase in rates is followed by a gradual decrease till a minimum appears at an uncommon pH value, where the percentage of the monoanion is however the maximum. The presence of the neutral form is also decided by knowing their fractions from the pK value at the above pH. Thus neutral form is however, not simple but is rather present as the zwitter ionic form. This is shown by the effect of solvent studies where lowering in rates occurs in spite of an increase in the polarity of the solvent. This is because the zwitterion if present, will form a transition state with the dispersion of charge present, as demanded by the decrease in rates by solvent effect study. The monoanion form, however is expected to form a polar transition state and this is strengthened by a changeover to a solvent of higher polarity leading to higher rates. Arrhenius parameters however require an unstable transition state for the bimolecular hydrolysis to proceed.</p> https://ultraphysicalsciences.org/paper/1318/ hydrolysis substituent on the stability phosphoradiamidic