Dielectric absorption of a few aromatic amines in a polystyrene matrix

1981 ◽  
Vol 59 (2) ◽  
pp. 232-237 ◽  
Author(s):  
S. P. Tay ◽  
S. Walker
Keyword(s):  
Aromatic Amines ◽  
Amino Group ◽  
Torsional Barrier ◽  
Dielectric Absorption ◽  
Enthalpy Of Activation ◽  
Polystyrene Matrix ◽  
Absorption Studies ◽  
Intramolecular Process ◽  
Nitrogen Bond

Dielectric absorption studies in the ranges 77–373 K and 102–107 Hz have been made on aniline, poly(4-aminostyrene), p-toluidine, 4-chloroaniline, 1-aminopyrene, and 4-aminobiphenyl in a polystyrene matrix. An intramolecular process has been observed in poly(4-aminostyrene) and 1-aminopyrene with enthalpies of activation of 25 and 26 kJ mol−1 respectively. The enthalpy of activation of the intramolecular process is of the same order as that found for the torsional barrier in aniline and 4-fluoroaniline. The most likely candidate for the intramolecular process appears to be rotation of the amino group about the carbon–nitrogen bond.

Acetyl group relaxation in four aromatic ketones

1977 ◽  
Vol 55 (4) ◽  
pp. 583-587 ◽  
Author(s):  
C. K. McLellan ◽  
S. Walker
Keyword(s):  
Energy Barrier ◽  
Benzene Solution ◽  
Far Infrared ◽  
Aromatic Ketones ◽  
Dielectric Absorption ◽  
Nmr Data ◽  
Polystyrene Matrix ◽  
Absorption Studies ◽  
Acetyl Group ◽  
Experimental Errors

Dielectric absorption studies have been made of group relaxation of acetophenone, 1,4-diacetylbenzene,4-acetylbiphenyl, and 2-acetylfluorene in a polystyrene matrix, and two rigid molecules have also been examined. For acetyl group relaxation in acetophenone, ΔHE = 29.6 ± 0.6 kJ mol−1 and ΔSE = 26 ± 3 JK−1 mol−1 (95% confidence intervals). The energy barrier for acetyl group relaxation is of the same order as that obtained from nmr data. Our results for acetophenone differ appreciably from the values reported for the gaseous phase by the far-infrared approach and from those by the dielectric absorption of aromatic ketones in benzene solution. The enthalpies of activation for acetyl group relaxation in 1,4-diacetylbenzene, 4-acetylbiphenyl, and 2-acetylfluorene are 29, 30, and 32 kJ mol−1, respectively, which values are identical within their experimental errors. These three substances have also been examined as pure solids, yielding enthalpies of activation for acetyl group relaxation of a similar magnitude.

Molecular and group relaxation studies in parasubstituted benzenes in various media

1979 ◽  
Vol 57 (21) ◽  
pp. 2843-2847 ◽  
Author(s):  
J. Crossley ◽  
J. P. Shukla ◽  
S. P. Tay ◽  
M. S. Walker ◽  
S. Walker
Keyword(s):  
Group Process ◽  
Activation Enthalpy ◽  
Small Contribution ◽  
Molecular Processes ◽  
Dielectric Absorption ◽  
Polystyrene Matrix ◽  
Absorption Studies ◽  
The Matrix ◽  
Intramolecular Motion ◽  
Relaxation Studies

Dielectric absorption studies have been made on molecules of the type [Formula: see text][Formula: see text] where X—Y is —OCH3, —COCH3, —CH2Cl, and —CH2CN. The molecules have been dissolved in (a) a polystyrene matrix and (b) in the viscous liquid o-terphenyl. For 1,4-dimethoxybenzene the group process dominates in both media, and estimates have been made of the activation enthalpy for group relaxation. For 1,4-dimethoxybenzene in benzene, decalin, Nujol, and o-terphenyl solutions, however, there appears to be a small contribution from the molecular process. No such contribution was detected in the matrix studies on this solute molecule. For 1,4-diacetylbenzene, 1,4-bis(chloromethyl)benzene, and 1,4-bis(cyanomethyl)benzene in o-terphenyl solution it again seems that the group and molecular processes overlap. However, in polystyrene the enthalpies of activation which emerge are characteristic of the group relaxation process as determined by the nmr approach. Altogether, the work illustrates that o-terphenyl may be a useful solvent in helping to decide whether a solute has contributions from an intramolecular motion.

Activation energy for methoxy group relaxation

1978 ◽  
Vol 56 (13) ◽  
pp. 1800-1803 ◽  
Author(s):  
M. A. Mazid ◽  
J. P. Shukla ◽  
S. Walker
Keyword(s):  
Activation Energy ◽  
Aromatic Ring ◽  
Energy Barrier ◽  
Methoxy Group ◽  
Steric Effects ◽  
Molecular Process ◽  
Dielectric Absorption ◽  
Polystyrene Matrix ◽  
Absorption Studies ◽  
Methoxy Groups

Dielectric absorption studies hove been made on seven compounds which hove methoxy groups attached to an aromatic ring and on some related rigid molecules. The solutes hove been dispersed in a polystyrene matrix. In some cases, the absorptions due to the group and the molecular process have been separated completely, and this has permitted the estimation of more accurate Eyring enthalpies of activation for methoxy group relaxation. These values hove been compared with those in the literature and, on the whole, it would seem likely that the energy barrier to group relaxation is small and of the order of 10 kJ mol−1 for cases where there is no mutual conjugation or steric effects.

Dielectric Studies. Part XXXI. Analysis of the Dielectric Data of Phenol and its Polymerized Forms

1971 ◽  
Vol 49 (7) ◽  
pp. 1106-1114 ◽  
Author(s):  
M. D. Magee ◽  
S. Walker
Keyword(s):  
Dipole Moment ◽  
Relaxation Time ◽  
Mole Fraction ◽  
The State ◽  
Distribution Parameter ◽  
Dielectric Studies ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Dielectric Data ◽  
Intramolecular Process

The dielectric absorption and dispersions of several solutions of phenol in p-xylene have been measured at four microwave frequencies and at 2 MHz at a temperature of 25 °C. The data have been analyzed in terms of a mean relaxation time, a distribution parameter, and an apparent dipole moment which are useful empirical parameters for assessing the state of aggregation of the phenol molecules. The relaxation time at the lowest practicable concentration (0.02 mole fraction) is long for a molecule expected to relax predominantly by an intramolecular process. This and the behavior of the relaxation time and apparent dipole moment with increasing concentration are considered in terms of a model based on progressive association into an extended series of multimers, the trimer having a zero (or low) dipole moment and higher multimers becoming increasingly flexible.

Dielectric studies. Part XXIII. Relaxation data and apparent dipole moments of aniline and some disubstituted aromatic amines

1969 ◽  
Vol 47 (4) ◽  
pp. 681-686 ◽  
Author(s):  
S. W. Tucker ◽  
S. Walker
Keyword(s):  
Aromatic Amines ◽  
Dipole Moments ◽  
Frequency Dispersion ◽  
Dielectric Studies ◽  
Relaxation Data ◽  
Time Model ◽  
Electric Dipole Moments ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Dielectric Results

Dielectric studies have been carried out at microwave frequencies on dilute solutions of aniline, p-chloro-, p-bromo-, and m-chloro-anilines, and o-, m-, and p-toluidines at 25 °C in cyclohexane and p-xylene. The static dielectric constant has also been measured at 2 MHz. In addition o- and m-toluidines have been measured at 50 °C and p-toluidine at 15, 35, and 50 °C.The dielectric results, particularly those at 70.01 GHz, establish that there is more than one relaxation process present and the data have been analyzed on a two relaxation time model, the longer of which τ1, is identified as molecular relaxation. The cause of the lower electric dipole moments found from this method as opposed to the non-dielectric absorption methods is discussed. It follows that there is either an additional higher frequency dispersion or (and) a high atomic polarization for aniline and o-, m-, and p-toluidines. Work at still higher frequencies is required to study this further and to establish more precise values of τ2.

scholarly journals IMMUNOLOGIC PRODUCTION OF ANTIANGIOTENSIN

1960 ◽  
Vol 111 (3) ◽  
pp. 419-427 ◽  
Author(s):  
Sharad D. Deodhar
Keyword(s):  
Biological Activity ◽  
Angiotensin Ii ◽  
Aromatic Amines ◽  
Free Amino ◽  
Parent Compound ◽  
The Other ◽  
Amino Group ◽  
Angiotensin I ◽  
Absolute Requirement ◽  
Specific Activities

Angiotensin II was coupled with bovine γ-globulin (BGG) through the following series of reactions. See PDF for Structure By determinations of the aromatic amine and tyrosine contents of p-aminobenzoylangiotensin II, the number of p-aminobenzoyl residues introduced per molecule of angiotensin II was calculated. Absorption spectra (between 250 and 500 mµ) of BGG complexes of p-aminobenzoylangiotensin II and six different para substituted aromatic amines were compared. Specific activities (dog units/millimicromole) of the different intermediate products were determined. Presence of a terminal, free amino group does not appear to be an absolute requirement for the biological activity of angiotensin II, since substitution of a p-aminobenzoyl radical in this group yields a product with 40 to 50 per cent of the activity of the parent compound. Angiotensin I, on the other hand, is completely inactivated under identical circumstances. Possible implication of this finding has been discussed.

scholarly journals Mechanisms and products of azo coupling in histochemical protease procedures based on primary aromatic amines as unspecific moieties.

1990 ◽  
Vol 38 (9) ◽  
pp. 1295-1300 ◽  
Author(s):  
H G Frank
Keyword(s):  
Azo Dyes ◽  
Aromatic Amines ◽  
Elevated Temperatures ◽  
Test Tube ◽  
Aromatic Nucleus ◽  
Diazonium Salts ◽  
Amino Group ◽  
Tissue Sections ◽  
Primary Aromatic Amines ◽  
Methylated Amines

It is presumed that the azo dyes generated by histochemical protease reactions are formed by substitution of a reactive aromatic carbon. They are referred to as dyes of the C-azo series. To confirm this assumption, the absorption spectra between 330 and 630 nm of azo dyes resulting from coupling between various aromatic amines of the aniline and naphthylamine series and the diazonium salts Fast Blue B and Fast Garnet GBC were studied in test tube experiments. Some of the amines were blocked by methylation to prevent coupling either at the amino group (N-methylated) or at the aromatic nucleus (C-methylated). Coupling was performed in buffered aqueous solutions of the diazonium salts. For analysis the azo dyes were dissolved in dimethylformamide. For acid rearrangement these solutions were acidified and incubated at elevated temperatures. After detection of dipeptidyl peptidase IV in tissue sections using Gly-Pro-4-methoxy-2-naphthylamine as substrate, the resulting dye was extracted and compared with the test tube compounds. All aromatic amines yielded azo dyes. Dyes extracted from sections and those test tube compounds derived from unmethylated or C-methylated amines showed almost identical spectral maxima, whereas dyes formed by N-methylated amines yielded different spectra. Acid rearrangement did not influence the spectral maxima of the N-methylated amine-derived dyes. Dyes resulting from C-methylated amines were destroyed. The results indicate that under histochemical conditions diazonium salts react primarily with the liberated free amino group but not with the aromatic nucleus of the unspecific moiety. Therefore, it is proposed that the formula of the final reaction product in naphthylamine-based protease histochemistry should be given as an N-azo dye, e.g., as a triazene.

Meisenheimer complex formation between 4,6-dinitrobenzofurazan 1-oxide and primary, secondary and tertiary aromatic amines

1984 ◽  
Vol 37 (5) ◽  
pp. 985 ◽  
Author(s):  
RW Read ◽  
RJ Spear ◽  
WP Norris
Keyword(s):  
Complex Formation ◽  
Aromatic Amine ◽  
Aromatic Amines ◽  
Carbonate Solution ◽  
Complexation Reaction ◽  
Amino Group ◽  
Aromatic Carbon ◽  
Potassium Hydrogen Carbonate ◽  
Hydrogen Carbonate ◽  
Potassium Hydrogen

The uncatalysed formation of stable 1 : 1 Meisenheimer complexes between primary, secondary and tertiary aromatic amines and 4,6-dinitrobenzofurazan 1-oxide has been investigated. The thermodynamic product is derived from reaction through the aromatic carbon para or, if this position is substituted, ortho to the amino group of the aromatic amine. The complexes are stable to acid but react in aqueous potassium hydrogen carbonate solution or with aliphatic or aromatic amines to give crystalline salts of the complexes. In the presence of 1,4-diazabicyclo[2.2.2]octane, aniline reacts with 4,6-dinitrobenzofurazan 1-oxide to give an unstable nitrogen-bonded complex which is slowly converted into the carbon-bonded complex. The scope of the complexation reaction has been investigated and some of the mechanistic implications of the results are discussed.

Radical C‒N Borylation of Aromatic Amines Enabled by a Pyrylium Reagent

2019 ◽  
Author(s):  
Yuanhong Ma ◽  
Yue Pang ◽  
jan niski ◽  
Markus Leutzsch ◽  
Josep Cornella
Keyword(s):  
Aromatic Amines ◽  
Driving Force ◽  
Bond Cleavage ◽  
Radical Reaction ◽  
Radical Formation ◽  
Planar Structure ◽  
Amino Group ◽  
Aryl Radical ◽  
Electronic Environment

Herein, we report a radical borylation of aromatic amines through a homolytic C(sp2)‒N bond cleavage. This method capitalizes on a simple and mild activation via a pyrylium reagent (ScPyry-OTf) thus priming the amino group for reactivity. The combination of terpyridine and a diboron reagent triggers a radical reaction which cleaves the C(sp2)‒N bond and forges a new C(sp2)‒B bond. The unique non-planar structure of the pyridinium intermediate, provides the necessary driving force for the aryl radical formation. The method permits borylation of a wide variety of aromatic amines indistinctively of the electronic environment.<br>

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