T. Balakrishnan

Synthesis And Utility Of α,α'-bis (Triethyl Ammonium Methylene Chloride) β-Phenyl Ethene in Hydroxide Ion Initiated Reactions—A New Multi-Site Phase Transfer Catalyst

Abstract A three step synthesis of novel ‘multi-site’ water soluble phase transfer catalyst viz., α,α′-bis(triethyl ammonium methylene chloride) β-phenyl ethene and its utility in various organic biphase reactions are described.

Phase-transfer-catalyzed Darzen's condensation of chloroacetonitrile with cyclohexanone using aqueous sodium hydroxide and a new phase transfer catalyst

Abstract The kinetics of Darzens condensation of chloroacetonitrile with cyclohexanone has been studied under phase transfer catalytic conditions using aqueous sodium hydroxide as the base and 2-benzylidine- N , N , N , N ′, N ′, N ′-hexaethylpropane-1,3-diammonium dichloride as a new “multi-site” phase transfer catalyst (MPTC). The reactions were carried out at room temperature (29°C) under pseudo-first order conditions by keeping aqueous sodium hydroxide and cyclohexanone in excess and was monitored by GC. The effect of various experimental parameters on the rate of the reaction has been studied, and based on the results obtained, a suitable mechanism is proposed.

Phase-Transfer Catalysis: Free-Radical Polymerization of Methyl Methacrylate using K2S2O8-Quaternary Ammonium Salt Catalyst System. A Kinetic Study

Abstract The kinetics of phase-transfer-agent-assisted free-radical polymerization of methyl methacrylate using K2S2O8 as the water-soluble initiator and triethylbenzylammonium chloride (TEBA) as the phase-transfer catalyst (PTC) was investigated in toluene-water biphase media at 60°C. The effect of varying [MMA], [K2S2O8], [TEBA], [H+], the ionic strength of the medium, and the temperature on the rate of polymerization (R p) was studied. R p was found to be proportional to [MMA]2, [K2S2O8]1, and [TEBA]0.5. Based on the kinetic results, a mechanism involving initiation of polymerization by phase-transferred S2O8 2- and termination by Q+ (quaternary ammonium ion) is proposed.

Preparation and study of some copolyesters

Abstract Terephthalate unsaturated copolyesters with ethylene glycol and 2-butene-1,4-diol, with ethylene glycol and 2-butyne-1,4-diol, with ethylene glycol and diethylene glycol, and with 2-butyne-1,4-diol were synthesized by trans-esterification reactions. Proton nuclear magnetic resonance spectroscopy was used to elucidate the structures of the copolyesters. The intrinsic viscosities of the copolyesters were measured in o-chlorophenol at 30°C. The number-average molecular weights of these copolyesters were determined by using a vapor pressure osmometer. The thermal behaviors of the copolyesters were studied by differential thermal analysis and are discussed in terms of structural differences.

Preparation and characterization of poly(ethylene/tetramethylene terephthalate) copolyesters

Abstract Random copolyesters were prepared from dimethyl terephthalate (DMT), ethylene glycol (EG) and butane 1,4-diol (BD) by melt-polycondensation techniques, using varying amounts of EG and BD. Compositions have been established by 1H n.m.r. spectroscopy. Intrinsic viscosity and number average molecular weight ( M n ) were measured. Thermal properties have been studied by differential thermal analysis. Melting and crystallization temperatures and thermodynamic parameters are discussed in terms of structural differences, particularly the effect of composition and chain flexibility. The degree of crystallinity from differential thermal analysis, i.r. and wide angle X-ray scattering (WAXS) are discussed.

Polymer-supported reagents. II. Kinetics of esterification of acrylic acid with n-butanol using polymer supported titanium tetrachloride as catalyst

Crosslinked poly(4-vinylpyridine-co-styrene) was prepared and functionalized with titanium tetrachloride to afford the corresponding poly(4-vinylpyridine-co-styrene)-titanium tetrachloride complex. This insoluble functionalized polymer-supported catalyst shows good catalytic activity for esterification reactions. In this article, the kinetics of esterification of acrylic acid with n-butanol is reported. The rate of formation of product depends on many experimental parameters, viz., stirring speed, concentration of acrylic acid, catalyst amount, temperature, percent active site, percent crosslinking, and mesh size of the polymer catalyst. The reaction rates were found to increase with increase in the stirring speed, concentration of acrylic acid, catalyst amount, and temperature, and decreases with increasing percentage crosslinking and mesh size of the polymer beads.

Alternating copolymerization of 2-methyl-2-oxazoline with α-chloro- and α-bromoacrylic acids: 3. Synthesis, characterization and kinetics

Abstract New 1:1 alternating copolymers of 2-methyl-2-oxazoline with (i) α-chloroacrylic acid and (ii) α-bromoacrylic acid were synthesized and characterized by i.r., n.m.r. and the products of alkaline hydrolysis. The copolymerization occurred at a temperature of 60°C without any added catalyst or initiator. The copolymerization kinetics were studied and the order with respect to each monomer was found to be unity. A scheme for the copolymerization involving a zwitterion intermediate is proposed.

Preparation and study of terephthalate copolyester of ethylene glycol and butane-1,4-diol

SummaryRandom terephthalate copolyesters of ethylene glycol and butane-1,4-diol of various compositions were prepared by trans-esterification of poly(ethylene terephthalate) (PET) with butane-1,4-diol (BD). Proton nuclear magnetic resonance spectroscopy (NMR) was used to elucidate the structure and compositions of copolyesters. The thermal behaviour of the copolyesters were investigated by differential thermal analysis (DTA). Intrinsic viscosities were measured in orthochlorophenol at 30°C.

A modified method for the synthesis and characterization of a novel surface-enriched (with active site) polymer-supported phase transfer catalyst using vinyltoluene as a functionality and its catalytic efficiency in dichlorocarbene addition to olefines: A kinetic study

A modified method with respect to an earlier conventional procedure was successfully attempted and we now report the new procedure for the synthesis of surface-grafting technique by the delayed addition of inexpensive vinyltoluene (VT) functionality to the partially polymerized supporting monomers viz., styrene (St) and divinylbenzene (DVB) via suspension polymerization. The resulting copolymer beads containing surface-enriched with methyl group were converted into a catalyst by chlorination followed by a quaternization process. Two groups (I and II) of SE-PSPTC beads were prepared by fixing the crosslinking amount (DVB) as 2% and 6%, respectively, 25% of VT as a common active site functionality and the rest of the contribution was styrene. Each group contains six different catalysts based on the concentration of active sites on the surface which in turn depends upon the partial polymerization time (PPT) of St/DVB i.e., 0, 3, 6, 9, 12, and 15 hrs. These two different groups and 6 different catalysts categories in each were prepared with the objective to learn the influence of higher/lower crosslinking in the process of surface-grafting of poly(VT) on poly(St/DVB) and to determine the optimized partial polymerization time to bring the maximum active site on the surface. The level of enrichment of an active site of all the catalysts were determined through [chloride], FT-IR, SEM, EDAX, and ESCA analyses. The gradual increase of [chloride], C-N peak intensity from FT-IR, rough surface/nodules concentration from SEM, % of surface chloride from EDAX, decreasing/increase trend of surface carbon/surface chloride in ESCA analyses starting with 0 VT to 15 VT irrespective groups, confirms the gradual increase of active site on the surface beads based on the PPT. The results of [chloride], spectral analyses and the rate constants of all the catalysts in dichlorocarbene addition to various olefines ensure that 9 VT-SE-PSPTC was the best catalyst beads in both the groups due to its two-fold enhancement rather than the conventional catalyst (0 VT) of both groups although we had added the same amount of VT in both preparations.

PHASE TRANSFER CATALYZED FREE RADICAL POLYMERIZATION: KINETICS OF POLYMERIZATION OF ALKYL METHACRYLATES USING POTASSIUM PEROXOMONOSULPHATE/TETRABUTYL PHOSPHONIUM CHLORIDE CATALYST SYSTEM

The kinetics of phase transfer catalyzed free radical polymerization of alkyl methacrylates (MMA and EMA) using potassium peroxomonosulphate (water-soluble initiator) coupled with phase transfer catalyst viz., tetrabutylphosphonium chloride (TBPC) have been investigated in ethylacetate-water biphase system at 50 ± 0.1°C. The rate of polymerization increased with an increase in the quaternary salt concentration, but showed a tendency to level off at a higher concentration. An increase in peroxomonosulphate concentration also increased the rate of polymerization (Rp). The order with respect to monomer was found to be in unity. A square root order was observed for both peroxomonosulphate and phase transfer catalyst. A suitable kinetic scheme has been proposed to account for the experimental data and its significance is discussed.