Acompanha : Guia didático: a química na junk food: uma proposta para o ensino de ligações químicas por meio do enfoque CTS / O objetivo deste estudo é propor estratégias de ensino no enfoque CTS para o ensino de Ligações Químicas com ênfase nas Ligações Iônica e Covalente. Nesse sentido o presente estudo foi desenvolvido e aplicado em uma escola da rede pública de ensino do Paraná, na cidade de Telêmaco Borba, em duas turmas da segunda (2ª) série do ensino técnico integrado ao ensino médio, totalizando 42 alunos. A abordagem metodológica foi abordagem qualitativa, de natureza interpretativa com observação participante. Para a coleta de dados foram utilizados: fotos, gravações de arguições orais e vídeos de atividades transcritos na íntegra, anotações de campo em protocolos de observação das interações do dia-a-dia na sala de aula, questionários e atividades desenvolvidas pelos alunos. As atividades foram desenvolvidas em dezoito (18) aulas, as quais interligaram os conceitos químicos de Ligações Químicas ao tema social controverso (Junk Food), de forma a promover as inter-relações dos aspectos da ciência, tecnologia e sociedade. Os principais resultados obtidos evidenciaram que pelas atividades propostas, o ensino de Ligações Químicas, por meio do tema social Junk Food, promoveu a valorização do conhecimento científico extrapolando as barreiras da sala de aula para o contexto social dos educandos. Pois as atividades desenvolvidas nos módulos, proporcionou as relações entre os conteúdos escolares e os aspectos cotidianos dos alunos. Alcançando os objetivos da proposta CTS para a cidadania. Outro resultado alcançado compreende a elaboração de um guia didático que tem por objetivo compartilhar atividades desenvolvidas neste estudo, como sugestão metodológica para os profissionais que lecionam Química, e atuam no ano final do Ensino Fundamental, Ensino Médio e Técnico. / The aim of this study is to propose teaching strategies in CTS approach to teaching with emphasis on Chemical Bonds Ionic and Covalent Links . In this sense the present study was developed and applied in a public school teaching of Paraná, in the town of Telêmaco Borba , in two classes of the second ( 2nd ) series of technical education integrated into the school , totaling 42 students . The methodological approach was qualitative approach, interpretative participant observation . For data collection were used : photos , recordings and videos Pleas oral activities fully transcribed , field notes on observation protocols of interactions of day- to-day classroom , quizzes and activities for students . The activities we developed in eighteen (18) classes, which interlinked the chemical concepts of Chemical Bonds to controversial social issue (Junk Food), in order to promote inter - relations aspects of science, technology and society. The main results showed that the proposed activities, the teaching of Chemical Bonds, through social theme Junk Food, promoted the appreciation of scientific knowledge surpassing the barriers of the classroom to the social context of the learners. For the activities in the modules, provided the relationships between school subjects and everyday aspects of students. Achieving the goals of the proposed CTS for citizenship. Another result obtained includes the preparation of a didactic guide which aims to share activities developed in this study as methodological suggestion for professionals who teach chemistry, and act in the final year of elementary school, high school and technical.

No description available.

This study concerns halogen bonding between small molecules. Except where otherwise stated herein this investigation was performed exclusively using the M06-2X density functional, in conjunction with the 6-31+G* basis set except for iodine and astatine which were treated using the aug-cc-pVDZ-PP basis set with relativistic pseudopotentials. All calculations were performed in the gas phase. The counterpoise procedure was employed for all full geometry optimisations. Statistical analysis of the Cambridge Structural Database, wherein the frequency of structures as a function of halogen bond angle and distance constituted the sole part of this study not to be based on density functional theory. Except in chapter 5, all halogens from fluorine to astatine are investigated. In chapter 3, halogen bonding between halobenzene and a single water molecule is discussed. Competition between R – X•••OH2 halogen bonding and R – X•••H-O-H hydrogen bonding interactions is described. This system is analogous to the more elaborate microsolvated 1- methyl-5-halouracil system described in chapter 4. In this latter system one 1-methyl-5- halouracil molecule interacts with either one or two water molecules. A central feature of the investigation into this system is competition between R – X•••OH2 and R=O•••H-O-H hydrogen bonding. In chapter 5, halogen bonding is discussed in the context of the thyroid system. In particular halogen bonding between a thyroxine iodine atom and the protein backbone as well as crystal water molecules is the subject of this chapter. The effect of substitution of the iodine atom with an astatine atom is presented. Chapter 6 is concerned with halogen bonding in halogenated DNA base pairs. Interaction energies are compared with those of the canonical base pairs, and the effect of halogen bonding on geometry is also discussed. For each system, halogen bonding was found to become stronger and more tolerant of non- linear bond angles going down the halogen group.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Chemical bonds form the basis for understanding the formation and behavior of the substances in everyday life. The investigation focus of this survey was the teaching and learning of chemical bonds in high school, and the main objectives were to make a diagnosis of how the content is being developed at this level, as well as to investigate the process of knowledge construction by the students of the 1st year of high school, through a Teaching-Learning Sequence (TLS) and traditional teaching. In order to achieve such objectives this survey was conducted in two parts. In the first part there were three investigations which provided evidence of the importance given to chemical bonds in high school. Following the principles of qualitative survey the data were collected using instruments made from guidelines described in the literature or for the specific purposes of each investigation. In this part of the study we investigated: - the concepts of chemical bonds of 124 students of the 1st year of high school from two public schools and a private school in the region of Santa Maria, RS, who had already studied the topic formally in class; - The approach of the chemical bonds in textbooks (PNLD 2015-2017), through the analysis of chapters related to the topic of each title - The perception of four high school teachers and two professors about the chemical bonds education. The results provided the following picture: the topics chemical stability and nature of the interaction between atoms and ions are being developed inappropriately, by using models that cause conceptual distortions. Moreover, the traditional method prevails in class and teaching is focused on the transmission of content with the help of the textbook. Based on this, interventions were planned and developed focusing on the study of the chemical stability based on energy aspects and the electrostatic model for each type of interatomic bond. In the second part of the survey, the investigation of knowledge construction in chemical bonds occurred by monitoring four classes of the 1st year of high school, in a total of 50 subjects. The content was developed by school teachers in two classes through the TLS and the other two by the traditional method. For data analysis, it was considered Bachelard theory and four dimensions, which are: chemical stability, ionic bond, covalent bond, metallic bond. Initially, the conceptions of the students in each dimension were evaluated in philosophical areas and later in hierarchical levels. At the end of the survey, it was drawn an epistemological profile for each student from the assessment of the considered dimensions. Monitoring the ideas of the students, from the two contexts, throughout the study of chemical bonds revealed that the construction of knowledge happened by overcoming epistemological obstacles linked to realistic and empiricist philosophical areas. It was observed that most of the students from the TLS context (55,2%) and traditional (66,6%) had primarily a rational profile at the end of the survey. The results suggest that there is a relationship between the area of epistemological profile and the capacity of transition between the levels of representation of matter, as the explanations related simultaneously the macroscopic, submicroscopic and symbolic levels were given by the students who had rationalists profiles. In addition, there was an advantage of TLS in relation to the traditional context, related to the aptitude of the students to employ the three levels of representation at the same time. Finally, this study showed that it is important to have theoretical explicitness regarding the curriculum models and educational planning in order to obtain satisfactory results in the chemical bonds education. / As ligações químicas constituem a base para a compreensão da formação e do comportamento das substâncias presentes no cotidiano. O foco de investigação desta pesquisa foi o ensino e a aprendizagem das ligações químicas no ensino médio e os objetivos principais foram realizar um diagnóstico de como o conteúdo está sendo desenvolvido neste nível, bem como investigar o processo de construção do conhecimento pelos estudantes da 1ª série do ensino médio, por meio de uma Sequência de Ensino e Aprendizagem (SEA) e do ensino tradicional. Para alcançar tais objetivos, esta pesquisa foi desenvolvida em duas partes. Na primeira parte, foram realizadas três investigações que forneceram indícios do tratamento dado às ligações químicas no ensino médio. Seguindo princípios da pesquisa qualitativa, os dados foram coletados por meio de instrumentos elaborados a partir de orientações descritas pela literatura ou para os fins específicos de cada investigação. Nesta parte da pesquisa, investigou-se: - as concepções sobre ligações químicas de 124 estudantes da 1ª série do ensino médio de duas escolas públicas e uma privada da região de Santa Maria, RS, que já tinham estudado o tópico formalmente em sala de aula; - a abordagem das ligações químicas nos livros didáticos (PNLD 2015-2017), por intermédio da análise dos capítulos referentes ao tópico de cada obra; - a percepção de quatro professores do nível médio e dois professores universitários sobre o ensino de ligações químicas. Os resultados obtidos forneceram o seguinte panorama: os tópicos estabilidade química e natureza das interações entre átomos e íons estão sendo desenvolvidos de forma inadequada, por meio de modelos que provocam distorções conceituais. Além disso, a metodologia tradicional predomina nas aulas e o ensino está pautado na transmissão de conteúdos com auxílio do livro didático. Baseado nisso, foram planejadas e desenvolvidas intervenções com enfoque no estudo da estabilidade química fundamentado em aspectos energéticos e no modelo eletrostático para cada tipo de ligação interatômica. Na segunda parte da pesquisa, a investigação da construção do conhecimento em ligações químicas ocorreu mediante o acompanhamento de quatro turmas da 1ª série do ensino médio, totalizando 50 sujeitos. O conteúdo foi desenvolvido pelos professores regentes em duas turmas por meio da SEA e nas outras duas pelo método tradicional. Para a análise dos dados, considerou-se a teoria de Bachelard e quatro dimensões, que são: estabilidade química, ligação iônica, ligação covalente e ligação metálica. Inicialmente, as concepções dos estudantes em cada dimensão foram avaliadas em zonas filosóficas e posteriormente, em níveis hierárquicos. Ao final da pesquisa, foi traçado um perfil epistemológico para cada estudante a partir da avaliação das dimensões consideradas. O acompanhamento das ideias dos estudantes, dos dois contextos, ao longo do estudo das ligações químicas revelou que a construção do conhecimento se deu pela superação de obstáculos epistemológicos atrelados às zonas filosóficas realista e empirista. Detectou-se que a maior parte dos estudantes do contexto da SEA (55,2%) e tradicional (66,6%) apresentou um perfil majoritariamente racionalista ao final da pesquisa. Os resultados sugerem que existe relação entre a zona do perfil epistemológico e a capacidade de transição entre os níveis de representação da matéria, visto que as explicações que relacionaram, simultaneamente, os níveis macroscópico, submicroscópico e simbólico foram emitidas por estudantes que apresentaram perfis racionalistas. Além disso, observou-se uma vantagem da SEA, em relação ao contexto tradicional, quanto à aptidão dos estudantes em empregar concomitantemente os três níveis de representação. Por fim, este estudo evidenciou que é importante clareza teórica em relação aos modelos curriculares e planejamento didático para que se obtenham resultados satisfatórios no ensino de ligações químicas.

This thesis is centred around sequential C-C bond forming processes using oxygenated electrophiles. A major part of this research focuses on the constructive deoxygenation of 2-methoxyphenol (guaiacol), a major breakdown product of the renewable feedstock, lignin. 1,2-dielectrophiles are known to be challenging substrates for catalysis if both leaving groups are of similar reactivity, however high selectivity was observed in the palladium- catalysed Grignard cross-coupling of 2-methoxyphenyl-1H-imidazole-1-sulfonate. The previously untested Grignard cross-coupling catalyst, [PdCl₂(Xylyl-Phanephos)], was found to be highly active. A 2-benzoxazolyl functionality was shown to be an excellent directing group for the chelation-controlled nucleophilic aromatic substitution of aryl methyl ethers. However, this modified Meyers reaction is limited to aryl ethers containing an ortho-chelating group. To expand the ether scope, nickel-catalysed Grignard cross-coupling was studied. [NiCl₂(PⁿBu₃)2] showed increased activity in the Grignard cross-coupling of challenging ortho-substituted anisoles compared to the well-renowned [NiCl₂(PCy₃)2] and several Ni0 -NHC systems, with a ligand steric effect demonstrated. The success of [NiCl₂(PⁿBu₃)2] was extended to more activated methoxynaphthalene substrates, in which the lowest reported catalyst loadings (0.1-0.25 mol%) were reported. Induction periods at 0.1 mol% suggested the requirement of inorganic Lewis-acidic magnesium salts to be formed in situ before any considerable activity was observed. Further work is required to increase reaction and ether scope, but this work provides a basis for exploiting lignin- derived phenols as a framework in the synthesis of functionalised chemicals of higher value. The final results chapter concerns an alternative sequential C-C bond forming process using another oxygenated electrophile. [PdCl₂((S)-Xylyl-Phanephos)] was used to accomplish a Grignard cross-coupling of vinyl tosylate, with the product then subjected to a highly enantioselective methoxycarbonylation using the same catalyst. This lead to a concise synthesis of (S)-Flurbiprofen.

O carbono tipo diamante (DLC) é um material de revestimento que tem atraído grande interesse devido às propriedades de alta resistência ao desgaste e baixo coeficiente de atrito. Intercamadas contendo silício são amplamente utilizadas para melhorar a adesão do DLC em ligas ferrosas, embora o fenômeno que gera a adesão ainda não seja bem entendido. Neste contexto, o objetivo desse estudo é compreender claramente os fenômenos físico-químicos e as ligações químicas que são responsáveis pela adesão de filmes de DLC sobre aços, utilizando intercamadas contendo silício produzidas em diferentes condições de processamento. Os filmes foram depositados sobre o aço AISI 4140 por deposição química a vapor assistida por plasma pulsado de corrente contínua utilizando confinamento eletrostático. As intercamadas foram produzidas a partir de tetrametilsilano em diferentes tempos e temperaturas de deposição, e o filme de DLC foi subsequentemente depositado sobre as intercamadas a partir de acetileno, utilizando-se as mesmas condições experimentais para todas as amostras. A estrutura físico-química dos filmes produzidos foi avaliada por microscopia eletrônica de varredura, espectroscopia de Raios X por dispersão em energia, espectroscopia de emissão óptica por descarga luminescente e espectroscopia Raman. As ligações químicas nas interfaces do sistema aço/intercamada/DLC foram avaliadas por espectroscopia de fotoelétrons excitados por Raios X. Por fim, a carga crítica para delaminação dos filmes foi medida por testes de nanoesclerometria linear. Os resultados mostraram que a espessura e a estrutura química das intercamadas são dependentes do tempo e da temperatura de deposição, mas a temperatura foi estabelecida como o parâmetro chave de controle da cinética de reação e de crescimento da intercamada. A intercamada é estruturada como um carbeto de silício amorfo hidrogenado com formação preferencial de ligações Si–C em temperaturas de deposição a partir de 300°C. Para as amostras com intercamada depositada a partir dessa temperatura de transição, a adesão dos filmes de DLC é alcançada, sem delaminação espontânea. A melhora na adesão está associada com as ligações químicas formadas nas interfaces. Enquanto as ligações C–C e Si–C são formadas na interface intercamada/DLC, ligações Si–Fe são formadas na interface aço/intercamada. A presença de hidrogênio e oxigênio residual na estrutura da intercamada prejudica a adesão dos filmes de DLC. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-08-24T15:55:55Z No. of bitstreams: 1 Dissertacao Felipe Cemin.pdf: 4353174 bytes, checksum: 9667e1c8437438cfcf3fc9f8860b0fa6 (MD5) / Made available in DSpace on 2015-08-24T15:55:56Z (GMT). No. of bitstreams: 1 Dissertacao Felipe Cemin.pdf: 4353174 bytes, checksum: 9667e1c8437438cfcf3fc9f8860b0fa6 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico. / Diamond-like carbon (DLC) is a thin film material that has attracted much attention due to its properties as high wear resistance and super-low friction coefficient. Although silicon-based intermediate layers are employed to enhance the adherence of DLC films on ferrous alloys, the role of such buffer layers is not yet understood in chemical terms. In this context, the aim of this study is to clearly understand the physical-chemical phenomena and chemical bonding guaranteeing the DLC adhesion on ferrous alloys using Si-based interlayers deposited by different process conditions. The films were deposited on AISI 4140 steel by pulsed direct current plasma enhanced chemical vapor deposition assisted by electrostatic confinement. The interlayers were grown from tetramethylsilane at different deposition temperatures and times and the DLC thin film was grown from acetylene with the same experimental conditions for all samples. The physical-chemical structure of the bi-layers produced was evaluated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy and Raman spectroscopy. The local chemical bonds at the interfaces of the steel/interlayer/DLC structure were evaluated by X-ray photoelectron spectroscopy. Finally, the critical loads for thin films delamination were measured by nanoscratch testing. The results show that the interlayer thickness and structure are dependent on both deposition time and temperature, but the temperature was established as being the key parameter controlling the reaction kinetic and the interlayer growth. The interlayer is structured as a hydrogenated amorphous silicon carbide alloy with enhanced formation of Si–C bonds at deposition temperatures ≥ 300°C. At such transition temperature of interlayer deposition, adhesion of DLC is reached, with no spontaneous delamination. The improved adhesion is associated with the nature of chemical bonds formed in the interfaces. Whereas C–C and C–Si bonds are formed on the interlayer/DLC interface, the steel/interlayer interface is constituted by Si–Fe bonds. The presence of hydrogen and residual oxygen in the interlayer structure degrades the adhesion of DLC thin films.

Density functional (ca, BLYP, BPW91, B3LYP and B3PW91), MP2 and CCSD(T) methods in combination with LANL2DZ or cc-pVxZ-PP (where x=D(double), T(triple) Q(quadruple), and 5(quintuple)) basis sets have been employed in computing electronic transition energies of zinc and cadmium monomers. CCSD(T)/aug-cc-pV5Z-PP combination finds values that are 150 cm-1 from the experimental value for the zinc monomer and 240 cm-1 remove from the cadmium monomer excitation experimental value. These method/basis set combinations are also used to find spectroscopic values (re, De, we, wexe, Be , and Te) that rival experimental values for dimers and excimers. Examples of this can be seen with the CCSD(T)/aug-cc-pV5Z-PP combination phosphorescent emission results. The values found are within 120 cm-1 of the zinc emission energy and 290 cm-1 of the cadmium emission energy. While this combination rigorously models spectroscopic constants for monomers, dimers, and excimers, it does not efficiently model these constants for larger clusters with available modern computational resources. It is important to show spectroscopic trends (bonding, phosphorescent excitation and emissions) as clusters increase as the monomer and dimer emission energies do not model solid state metallophilic interactions and phosphorescence. The MP2/LANL2DZ combinations show qualitative cooperative bonding trends in group oligomers and extended excimers as size increases and shape change. Changes in excitation and emission energies are also shown as a function of size and shape of the clusters.

O carbono tipo diamante (DLC) é um material de revestimento que tem atraído grande interesse devido às propriedades de alta resistência ao desgaste e baixo coeficiente de atrito. Intercamadas contendo silício são amplamente utilizadas para melhorar a adesão do DLC em ligas ferrosas, embora o fenômeno que gera a adesão ainda não seja bem entendido. Neste contexto, o objetivo desse estudo é compreender claramente os fenômenos físico-químicos e as ligações químicas que são responsáveis pela adesão de filmes de DLC sobre aços, utilizando intercamadas contendo silício produzidas em diferentes condições de processamento. Os filmes foram depositados sobre o aço AISI 4140 por deposição química a vapor assistida por plasma pulsado de corrente contínua utilizando confinamento eletrostático. As intercamadas foram produzidas a partir de tetrametilsilano em diferentes tempos e temperaturas de deposição, e o filme de DLC foi subsequentemente depositado sobre as intercamadas a partir de acetileno, utilizando-se as mesmas condições experimentais para todas as amostras. A estrutura físico-química dos filmes produzidos foi avaliada por microscopia eletrônica de varredura, espectroscopia de Raios X por dispersão em energia, espectroscopia de emissão óptica por descarga luminescente e espectroscopia Raman. As ligações químicas nas interfaces do sistema aço/intercamada/DLC foram avaliadas por espectroscopia de fotoelétrons excitados por Raios X. Por fim, a carga crítica para delaminação dos filmes foi medida por testes de nanoesclerometria linear. Os resultados mostraram que a espessura e a estrutura química das intercamadas são dependentes do tempo e da temperatura de deposição, mas a temperatura foi estabelecida como o parâmetro chave de controle da cinética de reação e de crescimento da intercamada. A intercamada é estruturada como um carbeto de silício amorfo hidrogenado com formação preferencial de ligações Si–C em temperaturas de deposição a partir de 300°C. Para as amostras com intercamada depositada a partir dessa temperatura de transição, a adesão dos filmes de DLC é alcançada, sem delaminação espontânea. A melhora na adesão está associada com as ligações químicas formadas nas interfaces. Enquanto as ligações C–C e Si–C são formadas na interface intercamada/DLC, ligações Si–Fe são formadas na interface aço/intercamada. A presença de hidrogênio e oxigênio residual na estrutura da intercamada prejudica a adesão dos filmes de DLC. / Conselho Nacional de Desenvolvimento Científico e Tecnológico. / Diamond-like carbon (DLC) is a thin film material that has attracted much attention due to its properties as high wear resistance and super-low friction coefficient. Although silicon-based intermediate layers are employed to enhance the adherence of DLC films on ferrous alloys, the role of such buffer layers is not yet understood in chemical terms. In this context, the aim of this study is to clearly understand the physical-chemical phenomena and chemical bonding guaranteeing the DLC adhesion on ferrous alloys using Si-based interlayers deposited by different process conditions. The films were deposited on AISI 4140 steel by pulsed direct current plasma enhanced chemical vapor deposition assisted by electrostatic confinement. The interlayers were grown from tetramethylsilane at different deposition temperatures and times and the DLC thin film was grown from acetylene with the same experimental conditions for all samples. The physical-chemical structure of the bi-layers produced was evaluated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy and Raman spectroscopy. The local chemical bonds at the interfaces of the steel/interlayer/DLC structure were evaluated by X-ray photoelectron spectroscopy. Finally, the critical loads for thin films delamination were measured by nanoscratch testing. The results show that the interlayer thickness and structure are dependent on both deposition time and temperature, but the temperature was established as being the key parameter controlling the reaction kinetic and the interlayer growth. The interlayer is structured as a hydrogenated amorphous silicon carbide alloy with enhanced formation of Si–C bonds at deposition temperatures ≥ 300°C. At such transition temperature of interlayer deposition, adhesion of DLC is reached, with no spontaneous delamination. The improved adhesion is associated with the nature of chemical bonds formed in the interfaces. Whereas C–C and C–Si bonds are formed on the interlayer/DLC interface, the steel/interlayer interface is constituted by Si–Fe bonds. The presence of hydrogen and residual oxygen in the interlayer structure degrades the adhesion of DLC thin films.

The focus of this thesis is on C-O bonds activation by transition metal atoms. Lignin is a potential alternative energy resource, but currently is an underused biomass species because of its highly branched structure. To aid in better understanding this species, the oxidative cleavage of the Cβ-O bond in an archetypal arylglycerol β-aryl ether (β–O–4 Linkage) model compound of lignin with late 3d, 4d, and 5d metals was investigated. Methoxyethane was utilized as a model molecule to study the activation of the C-O bond. Binding enthalpies (ΔHb), enthalpy formations (ΔH) and activation enthalpies (ΔH‡) have been studied at 298K to learn the energetic properties in the C-O bond cleavage in methoxyethane. Density functional theory (DFT) has become a common choice for the transition metal containing systems. It is important to select suitable functionals for the target reactions, especially for systems with degeneracies that lead to static correlation effects. A set of 26 density functionals including eight GGA, six meta-GGA, six hybrid-GGA, and six hybrid-meta-GGA were applied in order to investigate the performance of different types of density functionals for transition metal catalyzed C-O bond cleavage. A CR-CCSD(T)/aug-cc-pVTZ was used to calibrate the performance of different density functionals.

Flash photolysis techniques were applied to studies of solvent displacement by Lewis bases (L) from solvated metal carbonyl complexes of Cr, Mo, and W. On the basis of extensive studies of the reaction rate laws, activation parameters , and linear-free-energy-relationships, it was concluded that the mechanisms of solvent displacement reactions depend on the electronic and steric properties of the solvents and L, as well as the identities of the metal atoms. The strengths of solvent-metal bonding interactions, varying from ca. 7 to 16 kcal/mol, and the bonding "modes" of solvents to metals are sensitive to the structures of the solvent molecules and the identities of the metal centers. The results indicate dissociative desolvation pathways for many arene solvents in (solvent)Cr(CO)_5 (solvent = benzene, fluorobenzene, toluene, etc.) complexes, and are consistent with competitive interchange and dissociative pathways for (n-heptane)M(CO)_5. Different types of (arene)-Cr(CO)_5 interactions were suggested for chlorobenzene (CB) vs. fluorobenzene and other non-halogenated arenes, i.e. via σ-halogen-Cr bond formation in the CB solvate vs. π-arene-Cr bond formation through "isolated" double bonds in solvates of the other arenes. The data also indicate the increasing importance of interchange pathways for solvent displacement from the solvates of Mo and W vs. that of Cr.