Anthocyanins are the natural plant pigments responsible for most of the red, blue and purple colors of flowers and fruit. One method of stabilization of the color of anthocyanins in nature is intramolecular copigmentation, in which a copigment molecule covalently attached to one of the sugar residues complexes with the anthocyanin cation chromophore. In the present work, two quantum chemical methodologies, time-dependent density functional theory (TD-DFT) and second.order algebraic diagrammatic construction (ADC(2)), were employed to predict the absorption spectra in vacuum and conductor-like screening model (COSMO) water of a natural anthocyanin containing an ester of coumaric acid (copigment) bound to the sugar residue of a cyanidin chromophore. ADC(2) in water adequately reproduces the experimental spectra with and without intramolecular copigmentation, pointing to this theoretical technique as a promising approach for predicting the spectroscopic properties of natural (and nature-inspired) dyes and pigments.

ABSTRACT An overview is provided of the status of research at the frontiers of investigation of the chemistry and photochemistry of two classes of natural plant pigments, the anthocyanins and the betalains, as well as of the pyranoanthocyanin pigments formed from anthocyanins during the maturation of red wine. Together, anthocyanins and betalains are responsible for almost all of the red, purple and blue colors of fruits and flowers and anthocyanins and pyranoanthocyanins are major contributors to the color of red wines. All three types of pigments are cationic below about pH 3, highly colored, non-toxic, reasonably soluble in water or alcohol and fairly stable to light. They exhibit good antioxidant or antiradical activity and, as part of our diet, confer a number of important health benefits. Systematic studies of model compounds containing the basic chromophoric groups of these three types of pigments are providing a deeper understanding of the often complex chemistry and photochemistry of these pigments and their relationship to the roles in vivo of these pigments in plants. These natural pigments are currently being exploited as starting materials for the preparation of novel semi-synthetic dyes, pigments and fluorescence probes.

Although the classical Fenton process exhibits a high initial rate of the organic compounds degradation, this process is not complete due to the formation of refractory compounds which resist the attack of the hydroxyl radicals. In the presence of Cu(II), the degradation is slower, but results in a greater reduction of TOC (total organic carbon) measurements of net mineralization at the end of the reaction (t=120min). The addition of Cu(II) ions to classical Fenton reaction conditions (Fe(II) plus H2O2 at pH 3) is shown to accelerate the degradation of organic compounds. This synergic effect causes an approximately 15% additional reduction of the TOC. Voltammetric studies confirm the catalytic role of catechol in the presence of Fe(III)/Fe(II) and Cu(II)/Cu(I). Addition of aliphatic acids to the reaction medium, did not interfere with the cupro-Fenton reaction, but had an inhibitory effect on the classical Fenton reaction, consistent with the following order of interaction with the ion Fe(III): Oxalic Acid (OA) >> Formic Acid (FA) ~ Acetic acid (AA).

Ionic detergent micelles have the capacity to solubilize organic substrates, interact selectively with counterions, repel coions, exhibit partial "dissociation" of the counterions, grow in size with added salt, affect the position of chemical equilibria, accelerate or inhibit the rates of chemical reactions, modulate photochemical reactivity and determine the dynamics of diffusion or near-diffusion controlled processes. Many of these phenomena can be understood and analyzed quantitatively in terms of relatively simple models for binding, selectivity and electrostatics that often require no knowledge of micellar structure or dynamics (the pseudophase limit), without compromising chemical intuition. An overview is provided of our current understanding of the interplay between micellar structure and electrostatics, selectivity, solubilization, and reactivity and their role in the development of quantitative formalisms for analyzing micellar effects on reactivity and equilibria.

A series of twelve novel 2-(pyrazol-1-yl)pyrimidine derivatives was easily obtained under ultrasonic conditions by the cyclocondensation reaction of 1-carboxamidino-pyrazoles with 4-methoxyvinyl-trifluoromethyl ketones using ethanol as an environment-friendly solvent in the presence of potassium hydroxide. Comparison of the ultrasound-promoted reaction with classical methodology shows that the former is faster and gives better yield. The products were isolated in excellent purity grades without purification by chromatography or recrystalization.

Números de agregação (N Ag) de micelas do detergente aniônico lauril éter sulfato de sódio (SLES), com duas subunidades de óxido de etileno, foram determinados a 30 e 40º C por supressão de fluorescência resolvida no tempo, utilizando pireno como sonda fluorescente e o íon N-hexadecilpiridíneo como o supressor. O crescimento das micelas de SLES induzido por sal (γ = 0,11-0,15, sendo γ a inclinação de um gráfico do log do número de agregação vs. log [Yaq] e [Yaq] a concentração de contraíons sódio livres na fase aquosa intermicellar) é significativamente menor do que o de micelas de alquilsulfato de sódio (γ ca. 0,25), uma diferença atribuída ao tamanho maior do grupo polar de SLES. A razão de intensidades vibrônicas I1/I3 e a constante de velocidade para a supressão intramicelar do pireno demonstram que a polaridade do microambiente de solubilização e a viscosidade intramicelar são insensíveis ao tamanho da micela ou à presença de sal.

Aggregation numbers (N Ag) of micelles of the commercial anionic detergent sodium lauryl ether sulfate (SLES), with an average of two ethylene oxide subunits, were determined at 30 and 40º C by the time-resolved fluorescence quenching method with pyrene as the fluorescent probe and the N-hexadecylpyridinium ion as the quencher. The added-salt dependent growth of SLES micelles (γ = 0.11-0.15, where γ is the slope of a plot of log aggregation number vs. log [Yaq] and [Yaq] is the sodium counterion concentration free in the intermicellar aqueous phase) is found to be significantly lower than that of sodium alkyl sulfate micelles (γ ca. 0.25), a difference attributed to the larger headgroup size of SLES. The I1/I3 vibronic intensity ratio and the rate constant for intramicellar quenching of pyrene show that the pyrene solubilization microenvironment and the intramicellar microviscosity are insensitive to micelle size or the presence of added salt.

Pontos de ebulição (T B) de alcinos acíclicos são preditos a partir de seus números de ponto de ebulição (Y BP) com a relação: T B(K) = -16,802Y BP2/3 + 337,377Y BP1/3 - 437,883. Os valores de Y BP, por sua vez, são calculados a partir da estrutura dos compostos utilizando a equação: Y BP = 1,726 + Ai + 2,779C + 1,716M3 + 1,564M + 4,204E3 + 3,905E + 5,007P - 0,329D + 0,241G + 0,479V + 0,967T + 0,574S. O valor de Ai depende do padrão de substituição do alcino e o restante da equação é o mesmo relatado anteriormente para alcanos. Para um conjunto de dados de 76 alcinos acíclicos, a correlação entre os valores de T B previstos e da literatura apresentou um desvio médio absoluto de 1,46K com um valor de R² de 0,999. Além disso, os valores de Y BP também podem ser utilizados para prever os pontos de fulgor dos alcinos.

Boiling points (T B) of acyclic alkynes are predicted from their boiling point numbers (Y BP) with the relationship T B(K) = -16.802Y BP2/3 + 337.377Y BP1/3 - 437.883. In turn, Y BP values are calculated from structure using the equation Y BP = 1.726 + Ai + 2.779C + 1.716M3 + 1.564M + 4.204E3 + 3.905E + 5.007P - 0.329D + 0.241G + 0.479V + 0.967T + 0.574S. Here Ai depends on the substitution pattern of the alkyne and the remainder of the equation is the same as that reported earlier for alkanes. For a data set consisting of 76 acyclic alkynes, the correlation of predicted and literature T B values had an average absolute deviation of 1.46 K, and the R² of the correlation was 0.999. In addition, the calculated Y BP values can be used to predict the flash points of alkynes.

As transições eletrônicas para os cátions flavílio e bases quinonoidais de dezessete sais deste cátion foram estudadas nos níveis semiempírico e DFT (teoria do funcional da densidade). O efeito do solvente nos espectros eletrônicos foi incluído pelo Modelo Contínuo Polarizado, PCM. As transições eletrônicas de menor energia foram assinaladas como transições HOMO -> LUMO. Ambos os níveis de teoria forneceram bons resultados para as transições eletrônicas dos cátions flavílio, enquanto apenas os cálculos por TDDFT-PCM puderam ser empregados para as transições das bases quinonoidais. Foram feitos cálculos de pKa absoluto para nove sais de flavílio em nível DFT. Os valores de pKa calculados pela nossa parametrização do PCM forneceram resultados excelentes, com um desvio médio absoluto de menos de meia unidade de pKa. Foram calculados por DFT potenciais de redução para cinco cátions flavílio. Os resultados teóricos encontrados ficaram em boa concordância com os resultados experimentais após a correção de um desvio sistemático.

The electronic transitions for flavylium cations and quinonoidal bases of 17 substituted flavylium salts have been studied at semiempirical and DFT (density functional theory) levels. Solvent effect on electronic spectra was included by Polarizable Continuum Model, PCM. We assigned longest-wavelength absorption maxima to HOMO -> LUMO transition. Both levels of theory gave good results for electronic transitions of flavylium cations whereas only TDDFT-PCM calculations could be used for electronic transitions of their quinonoidal bases. We also performed absolute pKa calculations of nine flavylium salts at DFT level. The pKa calculated values by our PCM parameterization gave excellent results with mean absolute deviation less than a half of one pKa unit. One-electron reduction potentials were carried out for 5 flavylium cations at DFT level. The theoretical results found were in good agreement with experimental values after adjustment for a systematic deviation.

Pressões de vapor de líquidos orgânicos (em Pa a 298 K) correlacionam (R² = 0.986) segundo a relação: log Pvap = 7.86 - 3.54 V - 1.17 E - 1.52 (S + lambda) - 3.64 (eta × A × B) sendo V, E, S, A, e B parâmetros empíricos para o volume molar, o índice de refração em excesso, a dipolaridade/polarizabilidade e a capacidade doadora e receptora de pontes de hidrogênio do soluto, respectivamente. O parâmetro lambdaajusta o valor do termo em S para grupos funcionais específicos, enquanto considera diferenças na formação de pontes de hidrogênio entre classes distintas de líquidos puros. Essa relação linear de energia livre (LSER) é quimicamente razoável e permite a previsão da pressão de vapor de líquidos orgânicos a partir de parâmetros de soluto conhecidos ou estimados a partir de estrutura química. Esses resultados ilustram o potencial de uso de parâmetros de soluto para desenvolver LSERs para a previsão de propriedades de substâncias puras.

Vapor pressures (in Pa at 298 K) of organic liquids were found to correlate (R² = 0.986) with empirical molecular parameters by the relationship: log Pvap = 7.86 - 3.54 V - 1.17 E - 1.52 (S + lambda) - 3.64 (eta × A × B) where V, E, S, A, and B are solute parameters developed by Abraham and coworkers representing, respectively, the characteristic volume, excess index of refraction, dipolarity/polarizability, and hydrogen bond donor and acceptor characteristics of the solute. The parameter lambda provides for modulation of the S term for specific functional groups, such as those with strongly dipolar structures, while the parameter eta takes into account differences in neat-liquid hydrogen bonding between classes of liquids. This linear free energy relationship (LSER), together with appropriate solute parameters taken from literature data or estimated from chemical structure, provides a convenient method for estimating the vapor pressure of pure organic liquids. This study also provides insight into the extent to which the LSER model may be extended to the prediction of properties of pure substances.

An historical overview is provided of the origins, growth and development of the field of photochemistry in Brazil, with special emphasis on the last three decades.