1 |
The Effect Of Potassium Hydroxide On The Polymerization Of Trichlorophenol, Pyrrole And Thiophene By Microwave InitiationUnsal Gungor, Elif Mufide 01 June 2008 (has links) (PDF)
The synthesis of black conducting polymer (CP) and/or crosslinked polymers
(CLP) and/or radical ion polymer (RIP) and/or white polymers (WP) and/or
orange polymer (OP) were achieved by using KOH with TCP, pyrrole and
thiophene via microwave energy in a very short time interval.
Polymerizations were carried out by constant microwave energy with different
time intervals varying from 1 to 25 min / or at constant time intervals with
variation of microwave energy from 90 to 900 watt / or varying the water content
from 0, 0.5 to 5 ml at constant time intervals and microwave energy, or at
constant time interval, water content, microwave energy with variation of
amount of KOH 0.03 mol to 6x10-4 mol. The effects of heating time, microwave
energy, water content and amount of KOH on the percent conversion and the
polymer synthesis were also investigated.White, orange polymers and radical ion polymers were characterized by FTIR
(Fourier Transform Infrared), 1H-NMR (Proton Nuclear Magnetic Resonance),
13C-NMR (Carbon-13 Nuclear Magnetic Resonance), TGA/ FTIR (Thermal
Gravimetric Analysis / Fourier Transform Infrared), DSC (Differential Scanning
Calorimeter), SEM (Scanning Electron Microscope), ESR (Electron Spin
Resonance), GPC (Gel Permeation Chromatography), UV-Vis (UV-Visible
Spectroscopy) and Light Scattering. Conducting and crosslinked polymers were
characterized by FTIR, TGA/ FTIR, DSC, SEM, ESR, XRD (Powder Diffraction
X-Ray) and conductivity.
|
2 |
Microwave Initiated Polymerization Of Trihalophenyleneoxide And AnilineLevent, Fulya 01 February 2011 (has links) (PDF)
The aim of the study is to synthesize poly(dibromophenyleneoxide) and polyaniline separately applying different microwave energies (90-900 watt), water amounts (1-5 ml) and time intervals (2-10 min) and investigate the effects of these parameters on the percent conversion of the polymers. The synthesis of poly(dibromophenyleneoxide) (P), radical ion polymer (RIP) and crosslinked polymer (CLP) were achieved by using tribromophenol (TBP) and Ca(OH)2 via microwave energy in a very short time interval.
P and RIP were characterized by ATR-FTIR, 1H-NMR, 13C-NMR, TGA-FTIR, ESR, GPC, UV-VIS, DLS and SEM. Crosslinked polymers were characterized by ATR-FTIR and TGA-FTIR and polyaniline was characterized by ATR-FTIR.
|
3 |
Microwave-assisted Simultaneous Novel Synthesis Of Poly(dibromophenylene Oxide)s, Poly(diiodophenylene Oxide)s (p), Conducting(cp) And/or Crosslinked (clp) And/or Radical Ion Polymers (rip)Celik, Guler (bayrakli) 01 March 2007 (has links) (PDF)
Microwave-assisted novel synthesis of poly(dibromophenylene oxide) or poly(diiodophenylene oxide) (P), conducting polymer (CP) and/or crosslinked polymer (CLP) and/or radical ion polymer (RIP) were achieved simultaneously from lithium, sodium or potassium 2,4,6-bromophenolate or sodium 2,4,6-iodophenolate in a very short time interval.
Polymerizations were carried out by constant microwave energy with different time intervals varying from 1 to 20 min / or at constant time intervals with variation of microwave energy from 70 to 900 watt / or varying the water content from 0.5 to 5 ml at constant time intervals and microwave energy. Poly(dihalophenylene oxide) and radical ion polymers were characterized by FTIR (Fourier Transform Infrared), 1H-NMR (Proton Nuclear Magnetic Resonance), 13C-NMR (Carbon-13 Nuclear Magnetic Resonance), TGA/ FTIR (Thermal Gravimetric Analysis / Fourier Transform Infrared), DSC (Differential Scanning Calorimeter), SEM (Scanning Electron Microscope), ESR (Electron Spin Resonance), GPC (Gel Permeation Chromatography), UV-Vis (UV-Visible Spectroscopy), Light Scattering and Elemental Analysis. Conducting and crosslinked polymers were characterized by FTIR, TGA/ FTIR, DSC, SEM, ESR, XRD (Powder Diffraction X-Ray) and Elemental Analysis.
The effects of heating time, microwave energy and water content on the percent conversion and the polymer synthesis were also investigated.
|
4 |
Mechanisms of the Intriguing Rearrangements of Activated Organic SpeciesHarman, David Grant, harmandg@hotmail.com January 2003 (has links)
The β-acyloxyalkyl radical rearrangement has been known since 1967 but its
mechanism is still not fully understood, despite considerable investigation. Since the
migration of a β-trifluoroacetoxy group generally proceeds more rapidly and with more varied regiochemistry than its less electronegative counterparts, this reaction was studied
in the hope of understanding more about the subtleties of the mechanism of the β- acyloxyalkyl radical rearrangement. The mechanism of the catalysed rearrangement of Nalkoxy-
2(1H)-pyridinethiones was also explored because preliminary studies indicated that the transition state (TS) for this process was isoelectronic with TSs postulated for the β-acyloxyalkyl radical and other novel rearrangements.
¶
A kinetic study of the rearrangement of the 2-methyl-2-trifluoroacetoxy-1-heptyl
radical in solvents of different polarity was undertaken using a radical clock method. Arrhenius equations for the rearrangement in each solvent were: hexane, log10[kr (s-1)] =
11.8±0.3 – (48.9±0.7)/ θ; benzene, log10[kr (s-1)] = 12.0±0.2 – (43.7±0.8)/ θ; and
propionitrile, log10[kr (s-1)] = 11.9±0.2 – (42.0±0.3)/ θ. Rate constants at 75˚C were:
hexane, kr = 2.9 × 104; benzene, kr = 2.8 × 105; and propionitrile, kr = 4.0 × 105 s-1.
The equilibrium constant for the reversible rearrangement at 80°C in benzene was 15.1 <K < 52.9.
¶
A regiochemical study with oxygen-labelled radicals revealed that trifluoroacetoxy
group migration occurs with 66-83% label transposition (3,2 shift). The proportion of
3,2 shift is decreased by polar solvent, high temperature and low concentration of the
reducing agent. Results of labelling experiments were consistent with cooperative 1,2
and 3,2 shifts, the former having Ea 9.5 kJmol-1 higher than the latter in benzene
solution.
¶
An esr study of nine β-oxygenated radicals revealed that the temperaturedependent
equilibrium conformation is controlled by a balance between steric and
stereoelectronic effects. The influence of the latter is increased by electron-attracting β-
substituents. Barriers to C α–C β rotation in β-oxyethyl radicals are approximately the same as for the propyl radical. Consequently, there is no significant through-space
interaction between the β-substituent and the unpaired electron.
¶
Experimental results were consistent with a mechanism involving a combination
of polarized 1,2 and 3,2 concerted shifts. The results may also be rationalised by the
intermediacy of a contact ion pair, as well as combinations of the three options.
¶
The rearrangement of N-alkoxy-2(1H)-pyridinethiones is catalysed by oxidants,
Lewis acids and protic acids. Pseudo first order kinetics are observed and there are
moderate solvent effects. The migration of a 1,1-dideuteroallyl group occurs almost
exclusively in a 1,4 sense. Migration of an enantiomerically enriched 1-phenylethyl
group proceeds with predominant retention of configuration in chloroform, but with
virtual racemisation in acetonitrile. Migrating groups do not become diffusively free
during the rearrangement. Substituents which stablise positive charge at C1 migrate more
rapidly. The bulk of evidence indicates that a catalyst activates the pyridinethione for
rearrangement by promoting aromatisation. Mass-spectrometric analysis of an isolated
intermediate and kinetic results are consistent with an intermolecular mechanism.
|
Page generated in 0.0688 seconds