Reversal of substituent effect on C=O stretching vibrations in hydantoin derivatives: Part II

1024-102

Reversal of substituent effect on electronic absorption spectra of <i>N</i>-(4-substituted phenyl)-benzamides in different solvents

206-210Absorption spectra of eleven N-(4-substituted phenyl)-benzamides have been recorded in ten solvents in the range 200-400 nm. The substituents at the phenyl nucleus are as follows: N (CH3)2, OCH3, CH3, H, Cl, Br, F, CN, CF3, COCH3 and NO2. The effects of substituents on the absorption spectra of investigated compounds are interpreted by correlation of absorption frequencies with simple and extended Hammett equation. When the electron-releasing substituents are attached to the nitrogen atom substituent effects are transmitted through the amide bond by the usual mechanism. However, the effect of electron withdrawing substituents appears to be quite opposite. The effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of linear solvation energy relationships using a general equation of the form v =vo + sπ* + bβ + aα, where π* is a measure of the solvent polarity, β is the scale of the solvent hydrogen bond acceptor basicities and α is the scale of the solvent hydrogen bond donor acidities. The results obtained for N-(4-substituted phenyl)benzamides are compared with the results for N-(4-substituted phenyl)-2-phenylacetamides under the same experimental conditions

A linear solvation energy relationship study for the reactivity of 2-substituted cyclohex-1-enecarboxylic and 2-substituted benzoic acids with diazodiphenylmethane in aprotic and protic solvents

The rate constants for the reaction of 2-substituted cyclohex-1-enylcarboxylic acids and the corresponding 2-substituted benzoic acids with diazodiphenyl methane were determined in various aprotic solvents at 30 ºC. In order to explain the kinetic results through solvent effects, the second order rate constants of the reaction of the examined acids were correlated using the Kamlet–Taft solvatechromic equation. The correlations of the kinetic data were carried out by means of multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and transition state. The signs of the equation coefficients support the proposed reaction mechanism. The quantitative relationship between the molecular structure and the chemical reactivity is discussed, as well as the effect of geometry on the reactivity of the examined molecules

Synthesis of azo pyridone dyes

Over 50% of all colorants which are used nowdays are azo dyes and pigments, and among them arylazo pyridone dyes (and pigments) have became of interest in last several decades due to the high molar extinction coefficient, and the medium to high light and wet fastness properties. They find application generally as disperse dyes. The importance of disperse dyes increased in the 1970s and 1980s due to the use of polyester and nylon as the main synthetic fibers. Also, disperse dyes were used rapidly since 1970 in inks for the heat-transfer printing of polyester. The main synthetic route for the preparation of azo dyes is coupling reaction between an aromatic diazo compound and a coupling component. Of all dyes manufactured, about 60% are produced by this reaction. Arylazo pyridone dyes can be prepared from pyridone moiety as a coupling component, where substituent can be on nitrogen, and diazonim salts which can be derived from different substituted anilines or other heterocyclic derivatives. In addition, arylazo dyes containing pyridone ring can be prepared from arylazo diketones or arylazo ketoesters (obtained by coupling β-diketones or β-ketoesters with diazonim salts) by condensation with cyanoacetamide. Disazo dyes can be prepared by tetrazotizing a dianiline and coupling it with a pyridone or by diazotizing aniline and coupling it with a dipyridone. Trisazo dyes can be also prepared by diazotizing of aniline and coupling it with a tripyridone or by hexazotizing a trianiline and coupling it with a pyridone. The main goal of this paper is to give a brief review on the synthesis of arylazo pyridone dyes due to the lack of such reviews. In addition, some properties of arylazo pyridone dyes as light fastness and azo-hydrazon tautomerism are disccused

Effect of substituents on the 1H-NMR chemical shifts of 3-methylene-2-substituted-1,4-pentadienes

The principle of linear free energy relationships was applied to the 1H chemical shifts of the b-vinyl proton atoms of 3-methylene-2-substituted-1,4-pentadienes. The correlations of the proton chemical shifts with Swain and Lupton substituent parameters provide a mutually consistent picture of the electronic effects in these compounds. The overall pattern of proton chemical shifts can be largely accounted for by a model of substituent effects based on field, resonance and p polarization effects. Owing to the particular geometric arrangement of the vinyl group in 3-methylene-2-substituted-1,4-pentadienes, the b-vinyl protons HB and HC have different sensitivities to polar and resonance effects. The different sensitivities of the 1H chemical shifts to resonance effects reveals some effects not predicted by the model outlined above. Evidence is presented that demonstrates that both the 1H and 13C chemical shifts for these compounds reflect their ground-state charge densities

Synthesis and investigation of solvent effects on the ultraviolet absorption spectra of 5-substituted-4-methyl-3-cyano-6-hydroxy-2-pyridones

A number of 5-substituted-4-methyl-3-cyano-6-hydroxy-2-pyridones from cyanoacetamide and the corresponding alkyl ethyl acetoacetates were synthesized according to modified literature procedures. The alkyl ethyl acetoacetates were obtained by the reaction of C-alkylation of ethyl acetoacetate. An investigation of the reaction conditions for the synthesis of 4-methyl-3-cyano-6-hydroxy-2-pyridone from cyanoacetamide and ethyl acetoacetate in eight different solvents was also performed. The ultraviolet absorption spectra of synthesized pyridones were measured in nine different solvents in the range 200400 nm. The effects of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of linear solvation energy relationships using a general equation of the form n = n0 + sp* + aa + bb, where p* is a measure of the solvent polarity, a is the scale of the solvent hydrogen bond donor acidities and b is the scale of the solvent hydrogen bond acceptor basicities

Investigation of the interfacial bonding in composite propellants. 1,3,5-Trisubstituted isocyanurates as universal bonding agents

A series of 1,3,5-trisubstituted isocyanurates (substituents: CH2CH2OH, CH2CH=CH2 and CH2CH2COOH) was synthesized according to a modified literature procedure. Experimental investigations included modification of the synthetic procedure in terms of the starting materials, solvents, temperature, isolation techniques, as well as purification and identification of the products. All the synthesized isocyanurates were identified by their melting point and FTIR, 1H NMR and UV spectroscopic data. Fourier transform infrared spectrophotometry was also used to study the interaction between ammonium perchlorate, hydroxyl terminated poly(butadiene), carboxyl terminated poly(butadiene), poly(butadiene-co-acrylonitrile), poly(propylene ether), cyclotrimethylenetrinitramine and the compounds synthesized in this work, which can serve as bonding agents. The results show that tris(2-hydroxyethyl)isocyanurate is a universal bonding agent for the ammonium perchlorate/carboxyl terminated poly(butadiene)/cyclotrimethylenetrinitramine composite propellant system

Solvent effect on electronic absorption spectra of cyclohex-1-enylcarboxylic and 2-methylcyclohex-1-enylcarboxylic acids

The ultraviolet absorption spectra of cyclohex-1-enylcarboxylic acid and 2-methylcyclohex-1-enylcarboxylic acid were determined in six protic and nine aprotic solvents in the wavelength range from 200 to 400 nm. The position of the lmax of the two examined acids showed that the ultraviolet absorption maximums of cyclohex-1-enylcarboxylic acid were at consistently longer wavelengths in protic solvents than those of methylcyclohex-1-enylcarboxylic acid. The opposite was true in aprotic solvents. In order to explain the obtained results, the ultraviolet absorption frequencies of the electronic transitions in the carboxy carbonyl group of the examined acids were correlated using a total solvatochromic equation of the form: n = n0 + sp* + aa + bb, where p* is a measure of the solvent polarity, b represents the scale of solvent hydrogen bond acceptor basicities and a represents the scale of solvent hydrogen bond donor acidities. The correlation of the spectroscopic data was carried out by means of multiple linear regression analysis. The opposing solvent effects on the ultraviolet absorption maximums of the two examined acids were discussed

Substituent and solvent effects on the UV/vis absorption spectra of 3-<i>N</i>-alkyl-5-carboxy uracils

1137-1140Absorption spectra of ten 3-N-alkyl-5-carboxy uracils are recorded in fourteen solvents in the range 200-400 nm. The absorption frequencies of carboxy carbonyl electronic transitions are correlated by dual substituent parameter (DSP) treatment involving both polar (σ*) and steric (Es or vc) substituent constants. The effect of solvent polarity and solvent/solute hydrogen bonding interactions on the absorption spectra are interpreted by means of linear solvation energy relationships (LSER) using a general equation of the form v = vo + sπ* + bβ + aα where π* is a measure of the solvent polarity, β is the scale of the solvent hydrogen bond acceptor basicities and a is the scale of the solvent hydrogen bond donor acidities