| Summary: | 碩士 === 元智工學院 === 化學工程學系 === 85 === Organophosphazenes can be used as pressuried working fluids,
flame retardants and lubricant. Phase-transfer catalysis (PTC)
is considered a useful tool insynthesizing organic chemicals
from two immiscrible reaction. In the study ,phase-transfer
catalysis was carried out for the substitution reaction of
hexachlorocyclotriphosphazene ((NPCl2)3) and phenol in a
mulitphase system tosynthesize the partial (phenoxy)
chlorocyclotriphosphazene. The consumption of reactant and the
production of products is observed and studied during thecourse
of the reaction. There are three main topics which need to be
understood in studying the phase-transfer catalytic reaction,
including (i) the reactionrate in the organic phase, (ii)the
mass-transfer steps between the organic andaqueous phase , (iii)
the partition equilibrium of the catalysts between thetwo phase.
So the kinetics, mass-transfer effect and effect of
concentrationin each phase are discussed. Several rigid
conclusions were obtained:(1) Thereaction rate was dramatically
increasing by adding a small quantity ofphase-transfer catalyst.
The products of the partial (phenoxy) chlorocyclotriphosphazene
was separated by pressured column chromatograph and cooling
crystallization. On the basis of 31P NMR spectra ,the reaction
type belonging to a transion-nongeminal path. According to the
experimental data , the electronic effect and the steric effect
were empolyed to explain the reaction of an SN2 type of
mechanism. (2) Changing the initial concentration
ofhexachlorocyclotriphosphazene affected the value of pseudo-
first-orderreaction-rate constant. Hence, the reaction system
was controlled by both chemical-kinetics and mass-transfer
effects. The mass transfer of the catalyst between two phases
was investigated by a psedo-steady-state LLPTC model. Also, the
intrinsic reaction-rate constants of the series substitution and
the overall mass transfer coefficient of the catalyst from
organic phase to aqueous phase were determined by a combined
model. In addition, the corresponding energies,enthalpies and
entropies of activtion of the series substritution werealso
estimated.(3) Base on the experimental result, the relationship
between the functions of NaOH in a PTC reaction such as (i)
salting out the intermediateproduct of catalyst QY to the
organic phase and (ii)reducing the solvation between the
catalyst and water to improve the reactivity of active catalyst
in the organic phase,and the mass-transfer capability of the
catalyst between bothphases was clarified. (4) In order to
overcome the separating problem of the catalyst from the final
product ,the catalyst was immobilized on a polymer support,i.e.,
triphase catalyst .The polymer support is a copolymer of styrene
andchloromethylstyrene , using divinylbenzene as a crosslinking
agent. The masstransfer limitation influences the triphase
reaction rate. The particle diffusion and intrinsic reactivity
limit the displacement reaction in the organic phase. The film
diffusion of the aqueous phase limits in the ion-exchange step.
(5)In the present study, the NMR chemical shifts and
coupingconstant of cyclotriphosphazenes have been analyzed. I
found that chemical shift of cyclotriphosphazenes can be
calculated and predicted from partial chemical shift of
cyclotriphosphazenes.The coupling constant of
cyclotriphosphazenes are not regular than chemical shift.
Therefore, coupling constant difficult to be analysized in
synthesizing cyclotriphosphazenecompound.
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