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Polymer-Bound Dialkylaminopyridine Catalysts
Published in John R. Kosak, Thomas A. Johnson, Catalysis of Organic Reactions, 2020
James G. Keay, Eric F. V. Scriven
The superior catalytic abilities of 4-dialkylaminopyridines as acylation catalysts were first demonstrated over 20 years ago [1,2]. Since that time 4-dimethylaminopyridine (DMAP) has emerged as the preferred catalyst for a variety of synthetic transformations under mild conditions, particularly acylations, alkylations, silylations, esterifications, polymerizations, and rearrangements [3]. Its use has been particularly beneficial in the acylation of sterically hindered alcohols where only low conversions are possible under normal conditions [2]. Rate increases of 104 were observed in the benzoylation of 3-chloroaniline for DMAP versus pyridine [4].
Polymeric Matrix Systems for Drug Delivery
Published in Raj K. Keservani, Anil K. Sharma, Rajesh K. Kesharwani, Drug Delivery Approaches and Nanosystems, 2017
Ilić-Stojanović Snežana, Ljubiša Nikolić, Nikolić Vesna, Dušica Ilić, Ivan S. Ristić, Ana Tačić
For the application as drug carrier, poly(lactide) should be defined molecular weight. Thus, catalyst, which can reduce the polymer chain length, and small molecular weight compounds, that can significantly change the properties of PLA, are used in poly(lactide) synthesis (Ristić et al., 2013b). Pyridine, in the form of 4-(dimethylamino) pyridine (DMAP), is used as a catalyst for the regulation of poly(D,L-lactide) chains lengths. The high molecular weight poly(lactide) depolymerize with primary alcohols at 38°C in the solution and at 185°C in the mass. Poly(lactide) with desired molecular weight can be obtained by transesterification.
The influence of the ring system with mono/diester and imine links, and terminal unsaturated carbon chains on mesomorphism and their quantum-mechanical study
Published in Liquid Crystals, 2023
The purities of all chemicals including 4-hydroxybenzoic acid, the appropriate n-alkyl bromides, potassium hydroxide, methyl alcohol, hydrochloric acid, 4-hydroxybenzaldehyde, potassium hydroxide, dry acetone, dry ethyl acetate, malonic acid, dry pyridine, pipyridine, 4-amino benzoic acid, dry ethyl alcohol, glacial acetic acid, N,N′-dicyclohexylcarbodiimide (DCC), 4-dimethylaminopyridine (DMAP), dry tetrahydrofuran (THF), chromium trioxide, sulphuric acid and 4-allyl-2-methoxyphenol were above 99% assay and used as received. Solvents were purified by distillation and then dried using molecular sieves. Infrared absorption spectra were recorded on a Shimadzu IR-408 infrared spectrophotometer using potassium bromide pellets (KBr). 1H-NMR spectra were recorded on a Bruker Avance Neospectrometer (400 MHz) with tetramethyl silane [Si(CH3)4] as an internal reference and deuterated chloroform (CDCl3) as a solvent. The chemical shifts of the proton signals were recorded and quoted as δ (ppm). Mesophase transition temperatures were recorded using a polarising optical microscope (POM) equipped with a heating stage. Mesophase transition temperatures and the associated enthalpy and entropy changes were determined using a differential scanning calorimeter (Shimadzu DSC-60 plus system), at a scanning rate of 10°C min−1 and the transition enthalpies are recorded in kJ∙mol−1 throughout the paper.
Effect of terminal metamers and homologous with imine and ester groups on mesomorphism and their DFT study
Published in Liquid Crystals, 2022
Akshay Vyas, Rohit R. Koshti, H. N. Patel
4-Hydroxybenzaldehyde, appropriate n-alkyl halide, potassium carbonate, dry acetone, ethyl acetate, 4-hydroxybenzoic acid, glacial acetic acid, 1-methoxypropan-2-ol, 2-ethoxyethan-1-ol, 2-butoxyethan-1-ol, concentrated sulphuric acid, sodium hydrogen carbonate, N, N′-Dicyclohexylcarbodiimide (DCC), 4-Dimethylaminopyridine (DMAP), tetrahydrofuran (THF), methyl alcohol and ethyl alcohol were used as received except the solvents, all solvents were dried using the appropriate method before their usage. Ultraviolet radiation absorption spectra of prepared compounds were recorded on PerkinElmer UV/Vis Spectrometer Lambda 35 system using ethyl alcohol as a solvent. The structure of the compounds was determined by means of Proton Magnetic Resonance spectra on Brucker Avance Neo Spectrophotometer (400 MHz) with Tetra Methyl Silane (TMS) as an internal reference standard, the solution of the compounds was prepared in deuterated chloroform (CDCl3), and the chemical shift was estimated in ppm. Infrared absorption spectra were recorded on Shimadzu IR-408 infrared spectrophotometer using potassium bromide pallets. Differential scanning calorimetry data were carried out on Shimadzu DSC-60 plus system, calibrated with indium before the analysis. The scanning rate of the enthalpy measurement was 10°C∙min−1.
New Schiff’s base cinnamates/benzoates liquid crystals with lateral methyl substitutes: characterisation, mesomorphic behaviour and DFT calculation
Published in Liquid Crystals, 2022
Rohit R. Koshti, Akshay Vyas, Kaushik A. Patel, Hardik S. Patel, Madhur B. Patel, H. N. Patel
2-methylaniline, Nitric acid, Sulphuric acid, concentrated hydrochloric acid, 4-Hydroxybenzaldehyde, the appropriate n-alkyl halides, anhydrous potassium carbonate, dry acetone, ethyl acetate, Dry Pyridine, Pipyridine, Malonic acid, 4-hydroxybenzoic acid, Potassium hydroxide, Ethyl alcohol, glacial acetic acid, N,N′-Dicyclohexylcarbodiimide (DCC), 4-Dimethylaminopyridine (DMAP) and tetrahydrofuran (THF) were used as received. Distillation and drying of the solvent were done before using them. Infrared (IR) spectra were collected on Shimadzu IR-408 spectrophotometer using potassium bromide (KBr) pellets. Proton nuclear magnetic resonance (1H-NMR) spectra were obtained on a Bruker Avance Neospectrometer (400 MHz) using tetramethyl silane (TMS) as an internal reference. The chemical shifts are quoted as δ (ppm) downfield from the internal reference; Deuterated chloroform (CDCl3) was used as a solvent for all the compounds. The phase assignments and transition temperatures were determined by thermal polarising optical microscopy by means of polarising microscope (Leitz Laborlux 12 POL) equipped with a heating stage. Differential scanning calorimeter (DSC) Shimadzu DSC-60 plus system with a heating rate of 10°C min−1 was used to determine the enthalpies of transitions and reported in kJ.mol−1. The instrument was calibrated with pure indium as a standard.