PROXIMATE CHARGE CATALYSIS.
Item
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Title
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PROXIMATE CHARGE CATALYSIS.
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Identifier
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AAI8319752
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identifier
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8319752
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Creator
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CINCOTTA, JOSEPH JOHN.
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Contributor
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Paul Haberfield
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Date
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1983
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Organic
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Abstract
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The aminolysis rate constants have been determined for the esters p-nitrophenyl-(gamma)-trimethylammonium butyrate fluoborate(IV) and p-nitrophenyl hexanoate(VI), with the amines tetra-n-butylammonium taurinate, TBAT(V), and benzylamine in both 95.3 mole % dioxane-water (D-W) and water at 25(DEGREES)C. Second order hydrolysis rate constants (solv. H(,2)O) were also determined for each ester in the presence of hydroxide ion.;The aminolysis reactions which involved at least one uncharged reactant followed second order kinetics (rate = k{lcub}ester{rcub}{lcub}amine{rcub}) in D-W. The reaction of charged ester (IV) with TBAT(V) in D-W was found to obey the following two term rate law: rate = k(,1){lcub}RIP{rcub} + k(,2){lcub}RIP{rcub}{lcub}TBAT{rcub}. Pre-equilibrium formation of a reacting ion pair (RIP) between IV and V, is proposed to occur prior to the formation of the tetrahedral intermediate. The value of this ion pair equilibrium constant was determined to be 1.4. The rate determining breakdown of the tetrahedral intermediate was observed to occur by either of two pathways. One pathway (k(,1)) involved direct breakdown of the intermediate to its corresponding amide and p-nitrophenol, while the other pathway (k(,2)) involved proton transfer from the intermediate to a second molecule of amine prior to its breakdown (this accounts for dependence of k(,2) on the TBAT concentration). The individual rate constants k(,1) and k(,2) for this special case were found to be 1.880 ((+OR-) 0.20) x 10('-2) sec('-1) and 41.15 (+OR-) 0.75 liter mole('-1)sec('-1) respectively. The catalytic influence, of pre-equilibrium complex formation between the charged reactant molecules (via electrostatic attraction) in D-W has been estimated to be > 10('2).;In Part II of this work, the equilibrium expression associated with the proton transfer from p-nitrophenol to TBAT(V) in 95. ('(TURN))3 mole % dioxane-water was found to consist of two distinct equilibria (K and K(,d)). The initial equilibrium (K) involved proton transfer to the amine, and formation of a small ion aggregate. The subsequent equilibrium (K(,d)) involved the dissociation of this ion aggregate into p-nitrophenoxide-tetra-n-butylammonium ion pair and taurine (zwitterion). The equilibrium constants for K and K(,d) were evaluated and found to be 3.5727 (+OR-) 0.0746 liter mole('-1) and 1.7304 ((+OR-) 0.168) x 10('-7) mole liter('-1) respectively.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Chemistry
