A reação de 1,2-dicloro-4,5-dinitrobenzeno (DCDNB) com OH- aquoso produz (após acidificação) 2-nitro-4,5-diclorofenol com perda de NO2. No entanto, com OH- > 2 mol L-1, DCDNB foi recuperado devido à formação do complexo estável 3,6-di-hidroxi Meisenheimer (M2-), e que em ácido, reverteu ao reagente inicial. A formação rápida do complexo mono-hidroxi Meisenheimer (M1-) pode ser acompanhada em DMSO:H2O 7:3 v/v e as constantes para sua interconversão com DCDNB e formação e retorno com M2- foram estimadas, com evidência destas reações em DMSO:H2O 1:1 v/v e H2O. A troca rápida de hidrogênio em OD- /D2O limita o uso da técnica de ressonância magnética nuclear (NMR) de¹ H na identificação de intermediários. Sinais de RMN de¹ H e13 C para o di-hidroxi Meisenheimer foram observados em DMSO-H2O-KOH. Existe evidência da formação de radicais livres em DMSO:H2O 4:1 v/v, e a cinética global em meio mais aquoso foi tratada considerando a existência transitória de pares de radicais aniônicos.

The reaction of 1,2-dichloro-4,5-dinitrobenzene (DCDNB) with aqueous OH- produces (after acidification) 2-nitro-4,5-dichlorophenol with loss of NO2. Nevertheless, with > 2 mol L-1 OH-, only DCDNB was recovered due to the formation of the long-lived 3,6-dihydroxy Meisenheimer complex (M2-), and that in acid, reverted to the starting material. Fast formation of monohydroxy Meisenheimer complex (M1-) can be followed in DMSO:H2O 7:3 v/v and rate constants for its interconversion with DCDNB and for formation and return with M2- complex were estimated, with evidence for these reactions in DMSO:H2O 1:1 v/v and H2O. The rapid hydrogen exchange in OD- /D2O limits the use of¹ H nuclear magnetic resonance (NMR) spectroscopy in identifying intermediates. ¹ H and13 C NMR signals of M2- complex were observed in DMSO-H2O-KOH. There is evidence for the formation of free radicals in DMSO:H2O 4:1 v/v, and overall kinetics in more aqueous medium were treated in terms of the transient existence of anionic radical pairs.

The main objective of this paper is to start and stimulate reflection, discussion and proposing actions that allow Chemistry in Brazil contribute to a prosperous, safer and better future for the nation.

This review presents the recent applications of some trihalomethyl carbinols, α,α,α-trihalogenated carbonyl compounds and trichloro(bromo)methyl-containing heterocycles, acting as high versatile synthetic precursors in organic chemistry, based on the last 10 years' literature.

Poor standards in schools and the increase in the number of institutions of higher education - frequently without the due control - have adversely affected the quality of university level education in Brazil. On the other hand, evaluation of undergraduate courses, which has been carried out regularly since the min 1990's allow, within certain limits, a description of the quality Brazilian higher education courses in general, and Chemistry courses in specific. This paper evaluates the results of the national examinations (2000 and 2003's ENC, and 2005's ENADE), attrition rates for the 1990's and for the 2000-2005 period, as well as the perceptions of students and instructors that took part in those exams. Furthermore, the paper also analyzes the opinions of academics and of private sector professionals about the educational system's capacity to meet the job market's demand for skilled labor force. The actual profile of Chemistry graduates is then compared to what is demanded from them by the market, revealing deficiencies in the educational system. The expected essential curricula changes that would introduce an innovative and advanced approach in the undergraduate courses have become great challenges. In this sense, the paper seeks to reflect on questions such as: How to give informative courses a formative emphasis? Which programs should be included in the curricula to involve students in activities that require initiative and decision-making, thus fostering both learning and interest in Chemistry? How to prepare instructors for schools and for higher education? How to increase instruction in related areas without expanding the curricula excessively? How to introduce entrepreneurship in the curricula and further awareness of the professional non-academic careers in the area?

1,2-dichloro-4,5-dinitrobenzene (DCDNB) reacts with primary and secondary amines, in acetonitrile, at room temperature, to give a monosubstituted nitro product with a yield of 85 to 95%. The chloro-nitro-disubstituted product is formed with excess amine under reflux. Piperidine, pyrroline, dimethylamine and methylamine were the most reactive reagents in both mono- and disubstitution.

Over the past years the Brazilian Chemical Society (SBQ) has been working on different projects related to the development of Chemistry in Brazil. After a discussion throughout the country two documents have been published in Quimica Nova: "Mobilizing Axes in Chemistry" and "The Chemist's Education". Here, we describe the initial document which was the starting point for the discussion of a new series of papers published in this special issue of Quimica Nova which presents an overview of the Chemistry in our country and the perspectives and needs for the next decade.

The discussions sponsored by the Brazilian Chemical Society, over the past five years, intending to produce a chemistry agenda with perspectives and needs for the next decade for the country, have involved the national chemistry community and several related sectors of Brazilian society. Chemistry education has been the theme throughout these discussions. It is known that the low level of basic and secondary education and the recent increase in high school courses and institutions adversely affect the quality of undergraduate teaching. The recent national "Curriculum Guidelines" for Chemistry Courses, through their flexible approach, encourage the integral, interdisciplinary (non compartmentalized) and critical-reflexive training of professionals as citizens and as entrepreneurs. However, deficiencies are still recognized. The system of undergraduate course evaluation has identified the most fragile modalities of the courses and other indicators. Also, it has been verified that the Brazilian chemistry industry absorbs only minimally the highly qualified professionals, which is attributed to the fact that the Federal Council of Chemistry is vertically organized and does not recognize the graduate degrees as professional qualifications. In conclusion, the importance of the effective implantation of the national curriculum guidelines is apparent, among other aspects, highlighting courses whose didactical and pedagogical projects may offer a solid formation in Chemistry. However, at the same time the guidelines are comprehensive and general enough to enable the chemistry professionals to develop varied skills.

Training of highly qualified personnel is the most transversal axis among those identified in the document "Mobilizing Axes in Chemistry", published by SBQ, in 2002, which demands to deep the discussions, initiated in the symposium "The Chemist's Education", whose main objective was to discuss the repercussions of that training in the teaching and in the industrial section. After the publication of an initial paper, a couple of meetings and workshops held in Rio de Janeiro, in December 2003, involving the national chemist community, discussed the "The role of the graduate degrees in the Chemist's Education" and "The Chemist's Education", and confirmed the need to invest in the formation of qualified human resources in profusion and in all levels. Actions to be taken were delineated. Presently, the graduate programs in Chemistry are showing expressive results. However, although these professionals are mostly absorbed by the academy (the absorption of the industry is less significant), only a few programs give special attention to the didactical and pedagogical training. The regional decentralization is actually a tendency in most programs, but the interaction academy-economic activities is still a challenge. It is necessary to establish with the industrial section, the highly qualified professional's profile in Chemistry that the industry can absorb. The undergraduation is growing in number and quality, however still excessively concentrated in the Southeast area. The national "Curricula Guidelines" for Chemistry Courses, through its flexible approach, propitiate the integral, interdisciplinary (non compartmentalized) and critical-reflexive training of the professionals as citizens and as entrepreneurs. However, deficiencies are still recognized. The evaluation system of undergraduate courses has been able to identify the most fragile modalities of courses and other indicators. It was also verified that Brazilian chemistry industry absorbs minimally the highly qualified professionals, which is attributed to the fact that the Federal Council of Chemistry is vertically organized and does not recognize the graduate degrees as professional qualification. In the conclusion, it stands out, among other aspects, the importance of the effective implantation of the national curricula guidelines, bringing out courses whose didactical and pedagogical projects may offer a solid formation in Chemistry, but comprehensive and general enough to enable the Chemistry professionals to develop varied skills.

Over the last five years there have been significant changes in higher education in Brazil as well as in research funding. As a contribution to the development of Science and Technology, and aiming to portray Chemistry today in Brazil, in the context of last year´s elections for President, State Governors, National Congress and Legislative Chamber, the Directors and Consulting Council of the Brazilian Chemical Society, SBQ, initiated in 2002 a series of activities to produce a document entitled Mobilizing Axes in Chemistry. This discusses undergraduate and graduate teaching in Chemistry, a new model for research funding, and the overall state of the art, and future perspectives. Six mobilizing axes have been identified and discussed to date: 1. Training of highly qualified personnel; 2. Decentralization, and discouragement of institutional in-breeding; 3. Stimulation of entrepreneurship and interdisciplinarity; 4. A guaranteed budget for Science and Technology; 5. Proactive interaction of academics with economic activity; and 6. Removal of institutional bottle-necks of all sorts. The Brazilian Chemical Society hopes that the new administration will in the near future begin the task of improving the national education system and increase funding for Science and Technology.

O tautomerismo de cinco 2,2'-bis-benzimidazóis, simetricamente substituídos, [5(6),5'(6')-tetrametil- (1); 5(6),5'(6')-dimetil-(2); 5(6),5'(6')-dicloro- (3); 5(6),5'(6')-dimetoxi- (4) e 4(7),4'(7')-dimetil-2,2'-bis-benzimidazol (5)], foi estudado por espectroscopia de ¹H RMN, a várias temperaturas, e a influência dos substituintes nas barreiras energéticas de interconversão tautomérica, interpretada através de cálculos teóricos.

The tautomerism of five symmetrically substituted 2,2'-bis-benzimidazoles [5(6),5'(6')-tetramethyl- (1); 5(6),5'(6')-dimethyl-(2); 5(6),5'(6')-dichloro- (3); 5(6),5'(6')-dimethoxy- (4) and 4(7),4'(7')-dimethyl-2,2'-bis-benzimidazole (5)], was studied by means of ¹H NMR spectroscopy at variable temperatures, and the influence of the substituents on the energy barriers for tautomeric interconversion was interpreted with the aid of theoretical calculations.

Dois complexos binucleares de FeIII, obtidos a partir de um novo ligante polidentado (H2BPClNOL =N-(2-hidroxibenzil)-N-(2-piridilmetil)[(3-cloro)(2-hidroxi)] propilamina e contendo a unidade estrutural FeIII(m-alcoxo)2FeIII, foram caracterizados estruturalmente através de estudos cristalográficos e magneto-químicos. Os complexos [Fe2(BPClNOL)2(OAc)]ClO4 (1) [Fe2(BPClNOL)2(H2O)2](ClO4)2. 4H2O (2) diferem entre si pela presença de um grupo acetato em ponte entre os sítios de FeIII no complexo (1). O complexo contendo a ponte acetato apresenta constante de acoplamento antiferromagnético aproximadamente 20 % menor quando comparado ao complexo sem ponte acetato.

A new polidentade ligand, N-(2-hydroxybenzyl)-N-(2-pyridylmethyl) [(3-chloro)(2-hydroxy)]propylamine (H2BPClNOL), was synthesized and two Fe2III complexes containing the FeIII(m-alcoxo)2FeIII core were structurally and magnetically characterized. Complex [Fe2(BPClNOL)2(OAc)]ClO4 (1) differs from complex [Fe2(BPClNOL)2(H2O)2](ClO4)2.4H2O (2) by the presence of an acetate-bridge between the two iron centers. The complex with the acetate bridge is about 20 % less antiferromagnetically coupled than the complex without the acetate bridge.

As a result of a number of discussions on the quality of undergraduate courses in Brazilian universities, curricular directions have been proposed. We present herein the curricular directions for the Chemistry courses with respect to basic, professional and complementary contents and extra-class activities.