Trapping-Mediated Dissociative Chemisorption of Cycloalkanes on Ru(001) and Ir(111):  Influence of Ring Strain and Molecular Geometry on the Activation of C−C and C−H Bonds

2001 ◽  
Vol 123 (5) ◽  
pp. 929-940 ◽  
Author(s):  
Christopher J. Hagedorn ◽  
Michael J. Weiss ◽  
Tae Won Kim ◽  
W. Henry Weinberg
10.1002/jcc.2 ◽  
1996 ◽  
Vol 17 (16) ◽  
pp. 1804-1819 ◽  
Author(s):  
Attila Kov�cs ◽  
Istv�n Kolossv�ry ◽  
G�bor I. Csonka ◽  
Istv�n Hargittai

1982 ◽  
Vol 47 (11) ◽  
pp. 2996-3003
Author(s):  
Zdeněk Bastl

The work function changes of vacuum deposited molybdenum films caused by the chemisorption of propylene, acetylene, hydrogen and nitrogen were measured using the Kelvin vibrating capacitor method. During the hydrocarbon chemisorption, the work function increased in a low surface coverage region but decreased at the higher surface coverages. The saturation values of the work function changes corresponding to complete coverage of the surface by chemisorbed propylene and acetylene equal -0.08 eV and -0.42 eV, respectively. The observed dependences of the work function change on surface coverage are interpreted by the dissociative chemisorption of hydrocarbons on a limited number of surface sites which are simultaneously the sites of preferred adsorption. The extent of dissociation decreases in the adsorption with the increasing surface coverage. The results of the study of the work function changes induced by the hydrogen and nitrogen chemisorption enabled to draw several conclusions on the surface topography of the used films.


1989 ◽  
Vol 54 (3) ◽  
pp. 566-571 ◽  
Author(s):  
Jiří Pancíř ◽  
Ivana Haslingerová

A semi-empirical topological method was applied to a study of an Ir(112) surface as well as to both a nondissociative and dissociative chemisorption on this surface. In all cases studied an attachment of carbon to the surface is energetically more favorable than an attachment of oxygen. The preferential capture of the CO molecule on atop sites is remarkable. The capture on n-fold hollow positions as well as the dissociative chemisorption of carbon monoxide on the Ir(112) surface are energetically prohibited.


1990 ◽  
Vol 55 (8) ◽  
pp. 1907-1919
Author(s):  
Jiří Pancíř ◽  
Ivana Haslingerová

A semiempirical quantum-chemical topological method is applied to the study of the fcc (112) surfaces of Ni, Pt, Pd, Rh, and Ir and the nondissociative as well as dissociative chemisorption of carbon monoxide on them. On Ni, dissociative chemisorption is preferred to linear capture, whereas on Pd and Pt, linear capture is preferred although dissociative chemisorption is also feasible. On Rh and, in particular, on Ir, dissociative chemisorption is energetically prohibited. The high dissociative ability of the Ni surface can be ascribed to a rather unusual charge alteration and to the degeneracy of the frontier orbitals. Negative charges at the surface level are only found on the Ni and Pt surfaces whereas concentration of positive charges is established on the Rh and Ir surfaces; the Pd surface is nearly uncharged. Metals with negatively charged surfaces seem to be able to dissociate molecules of carbon monoxide. It is demonstrated that CO adsorption can take place on all metal surface sites, most effectively in the valley of the step. In all the cases studied, the attachment to the surface is found to be energetically more favourable for the carbon than for the oxygen.


Author(s):  
Wai-Kee Li ◽  
Hung Kay Lee ◽  
Dennis Kee Pui Ng ◽  
Yu-San Cheung ◽  
Kendrew Kin Wah Mak ◽  
...  

The First Edition of this book, which appeared in 2013, serves as a problem text for Part I (Fundamentals of Chemical Bonding) and Part II (Symmetry in Chemistry) of the book Advanced Structural Inorganic Chemistry published by Oxford University Press in 2008. A Chinese edition was published by Peking University Press in August in the same year. Since then the authors have received much feedback from users and reviewers, which prompted them to prepare a Second Edition for students ranging from freshmen to senior undergraduates who aspire to attend graduate school after finishing their first degree in Chemistry. Four new chapters are added to this expanded Second Edition, which now contains over 400 problems and their solutions. The topics covered in 13 chapters follow the sequence: electronic states and configurations of atoms and molecules, introductory quantum chemistry, atomic orbitals, hybrid orbitals, molecular symmetry, molecular geometry and bonding, crystal field theory, molecular orbital theory, vibrational spectroscopy, crystal structure, transition metal chemistry, metal clusters: bonding and reactivity, and bioinorganic chemistry. The problems collected in this volume originate from examination papers and take-home assignments that have been part of the teaching program conducted by senior authors at The Chinese University of Hong Kong over nearly a half-century. Whenever appropriate, source references in the chemical literature are given for readers who wish to delve deeper into the subject. Eight Appendices and a Bibliography listing 157 reference books are provided to students and teachers who wish to look up comprehensive presentations of specific topics.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Robert Christie ◽  
Adrian Abel

Abstract Disazoacetoacetanilide pigments, more commonly known as diarylide yellows, are the most important group of yellow classical organic pigments. They were commercialized in the early 20th century many years after the introduction of the structurally related monazoacetoacetanilides (Hansa yellows). The molecules adopt the bis-ketohydrazone tautomeric form. X-ray single crystal structure investigations have provided an insight into the influence of the molecular geometry and crystal packing arrangements in the solid state on the properties of the pigments in application. The synthesis of diarylide pigments is relatively straightforward, the conditions essentially following those used for the corresponding monoazo pigments, so that the products are economically priced. In the case of these disazo pigments, suitable aromatic amines (1 mol) are bis-diazotized and the resulting bis-diazonium salts reacted with acetoacetanilide coupling components (2 mol), the two azo coupling reactions occurring at the same time. They are by far the dominant group of yellow pigments used in printing inks, well-suited for most standard process yellow inks. They were formerly important in the coloration of plastics but are no longer recommended for polymers processed above 200 °C, under which conditions toxic decomposition products are formed. Diarylide yellow pigments are characterized by high color strength, good to excellent solvent fastness, and good chemical stability, although they generally show inferior lightfastness.


Author(s):  
Nicola A. Kiernan ◽  
Andrew Manches ◽  
Michael K. Seery

Visuospatial thinking is considered crucial for understanding of three-dimensional spatial concepts in STEM disciplines. Despite their importance, little is known about the underlying cognitive processing required to spatially reason and the varied strategies students may employ to solve visuospatial problems. This study seeks to identify and describe how and when students use imagistic or analytical reasoning when making pen-on-paper predictions about molecular geometry and if particular reasoning strategies are linked to greater accuracy of responses. Student reasoning was evidenced through pen-on-paper responses generated by high attaining, high school students (N = 10) studying Valence Shell Electron Pair Repulsion (VSEPR) Theory in their final year of chemistry. Through analysis and coding of students’ open-ended paper-based responses to an introductory task, results revealed that students employed multiple reasoning strategies, including analytical heuristics and the spontaneous construction of external diagrammatic representations to predict molecular geometry. Importantly, it was observed that despite being instructed on the use of VSEPR theory to find analytical solutions, some students exhibited preference for alternative reasoning strategies drawing on prior knowledge and imagistic reasoning; showing greater accuracy with 3D diagrammatic representations than students who used the algorithmic method of instruction. This has implications for both research and practice as use of specific reasoning strategies are not readily promoted as a pedagogical approach nor are they given credit for in national examinations at school level.


Sign in / Sign up

Export Citation Format

Share Document