DIELECTRIC RELAXATION STUDIES OF 1:1 COMPLEXES OF ALKYL METHACRYLATE WITH PHENOLS DERIVATIVES

ABSTRACT Dielectric absorption studies of H-bonded complexes of methyl methacrylate (MMA) and butyl methacrylate (BMA) with p-cresol, p-chlorophenol, 2,4-dichlorophenol and p-bromophenol have been studied at microwave frequency 9.37 GHz in dilute solution of carbon tetrachloride at 308K. Different dielectric parameters like dielectric constant ε′ and dielectric loss ε″ at microwave frequency, static dielectric constant ε o and dielectric constant ε ∞ at optical frequency have been determined. The validity of the single frequency equation of Higasi et al. for multiple relaxation time

Immunomodulatory role of Keratin 76 in oral and gastric cancer

Keratin 76 (Krt76) is an epithelial differentiation marker that is downregulated in oral squamous cell carcinomas, correlating with poor prognosis. Here the authors show that genetic ablation of Krt76 in a mouse model results in increased susceptibility to carcinogenesis via enhanced accumulation of Tregs

Wounding induces dedifferentiation of epidermal Gata6+ cells and acquisition of stem cell properties

Item does not contain fulltex

Dielectric relaxation studies of alkyl acrylates with phenol derivatives in carbon tetrachloride using microwave absorption techniques

54-59The dielectric relaxation of alkyl acrylates (methyl acrylate, ethyl acrylate and butyl acrylate) with phenol derivatives (p-cresol, p-chlorophenol, 2,4-dichlorophenol and p-bromophenol) has been measured at microwave frequency 9.37 GHz in dilute solution of carbon tetrachloride at 308K. Different dielectric parameters like dielectric constant Ɛ‛ and dielectric loss Ɛ‛‛ at microwave frequency, static dielectric constant Ɛ₀ and dielectric constant Ɛ∞ at optical frequency have been determined. The relaxation time and activation energy have been determined using the measured dielectric data. The results show a linear dependence of relaxation time on alkyl chain length of acrylic esters and acidity of phenol derivatives. Comparative study of free energy of activation for the dielectric relaxation and viscous flow suggests that the process of viscous flow involves greater interference by neighbours than does dielectric relaxation, as the latter takes place by rotation only whereas the viscous flow involves both rotational and translational motion. The validity of the single frequency equation of Higasi et al. Bull Chem Soc Japan, 44(1971)988. For multiple relaxation time τ₁ is found to be function of the hydrogen bonding strength of phenolic hydrogen whereas the group rotation relaxation time τ₂ is a function of the steric interaction of proton donor. The relaxation time is maximum at 50:50 mol% ratio

FTIR study of hydrogen bonding interactions between alkyl esters and hexanol, p-cresol in carbon tetrachloride

12-19The effect of hydroxyl group in hexanol and p-cresol on the carbonyl vibration of representative compounds belonging to methyl methacrylate, ethyl methacrylate and butyl methacrylate in carbon tetrachloride has been studied by FTIR spectroscopic method. The integrated intensities and change in dipole moments for O-H and C=O bonds were calculated. Utilizing Nash method, the formation constant and free energy of the 1:1 complexes have been calculated. The formation constant and free energy change values vary with chain length of acrylic esters, which suggests that the strengths of the intermolecular hydrogen bonds (O–H…O=C) are dependent on chain length of acrylic esters. The strength of the intermolecular C=O: HO bonds is shown to be dependent on the basicity of the C=O group of alkyl esters and the acidity of the proton donor

Spatial constraints govern competition of mutant clones in human epidermis

Deep sequencing technologies allow for the investigation of clonal evolution in human cancers. Here the authors, combining sequencing data from human skin with mathematical modelling and simulations, suggest that the spatial context of a mutation with respect to other mutant clones may lead to differential clonal evolution

Dielectric relaxation and dipole moment studies of hydrogen bonded complexes for enanthamide and valeramide with halogenated phenols using J-band microwave frequency

Dielectric investigations of hydrogen bonded complexes of Enanthamide and Valeramide with 4-bromophenol, 4-chlorophenol, 4-iodophenol and 4-fluorophenol in benzene were done at 303K, using a J-band (7.22GHz) microwave bench and dielectric relaxation setup. The permittivity of amides with halogenated phenol binary mixtures was measured in the microwave frequency range at temperatures ranging from 298K to 323K. At microwave frequencies; dielectric relaxation of ternary mixes of polar liquids in nonpolar fluids has been explored. Such investigations give useful information about the intermolecular and intramolecular interactions of solutes and solvent molecules. The dipole meter had a measurement frequency of 2MHz. The different parameters of dielectric, relaxation time ( τ _0 ) and the dipole moment ( μ ) has been evaluated using the single-frequency concentration Higasi approach. The fact that the relaxation time and molar free energy activation of the 1:1 molar ratio are greater than those of other higher molar ratios (i.e. 3:1, 2:1, 1:2, 1:3) confirms the presence of a 1:1 complex structure between the studied systems, as well as a complex formation between the free hydroxyl group of phenols and the carbonyl group of amides. The dielectric relaxation energy parameters (ΔF ε , ΔH ε and ΔS ε ) of amides with halogenated phenols in benzene have been computed and compared with the related viscosity parameters. A comparison of these two sets of characteristics reveals that dielectric relaxation, like viscous flow, may be thought of as rate process