scholarly journals Philicity and Fugality Scales for Organic Reactions

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Rodrigo Ormazábal-Toledo ◽  
Renato Contreras
Keyword(s):  
Organic Chemistry ◽  
Reaction Mechanisms ◽  
Organic Reactions ◽  
Organic Reaction ◽  
Reactivity Indices ◽  
Leaving Groups ◽  
Set Up ◽  
Definition Of ◽  
Complete Account

Theoretical scales of reactivity and selectivity are important tools to explain and to predict reactivity patterns, including reaction mechanisms. The main achievement of these efforts has been the incorporation of such concepts in advanced texts of organic chemistry. In this way, the modern organic chemistry language has become more quantitative, making the classification of organic reactions an easier task. The reactivity scales are also useful to set up a number of empirical rules that help in rationalizing and in some cases anticipating the possible reaction mechanisms that can be operative in a given organic reaction. In this review, we intend to give a brief but complete account on this matter, introducing the conceptual basis that leads to the definition of reactivity indices amenable to build up quantitative models of reactivity in organic reactions. The emphasis is put on two basic concepts describing electron-rich and electron-deficient systems, namely, nucleophile and electrophiles. We then show that the regional nucleophilicity and electrophilicity become the natural descriptors of electrofugality and nucleofugality, respectively. In this way, we obtain a closed body of concepts that suffices to describe electron releasing and electron accepting molecules together with the description of permanent and leaving groups in addition, nucleophilic substitution and elimination reactions.

Predicting Feasible Organic Reaction Pathways Using Heuristically Aided Quantum Chemistry

2018 ◽  
Author(s):  
Dmitrij Rappoport ◽  
Alan Aspuru-Guzik
Keyword(s):  
Quantum Chemistry ◽  
Reaction Mechanisms ◽  
Quantum Chemical ◽  
Organic Reactions ◽  
Reaction Pathways ◽  
Empirical Knowledge ◽  
Organic Reaction ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Wide Range

Studying organic reaction mechanisms using quantum chemical methods requires from the researcher an extensive knowledge of both organic chemistry and first-principles computation. The need for empirical knowledge arises because any reasonably complete exploration of the potential energy surfaces (PES) of organic reactions is computationally prohibitive. We have previously introduced the Heuristically-Aided Quantum Chemistry (HAQC) approach to modeling complex chemical reactions, which abstracts the empirical knowledge in terms of chemical heuristics—simple rules guiding the PES exploration—and combines them with structure optimizations using quantum chemical methods. The HAQC approach makes use of heuristic kinetic criteria for selecting reaction paths that are not only plausible, that is, consistent with the empirical rules of organic reactivity, but also feasible under the reaction conditions. In this work, we develop heuristic kinetic feasilibity criteria, which correctly predict feasible reaction pathways for a wide range of simple polar (substitutions, additions, and eliminations) and pericyclic organic reactions (cyclizations, sigmatropic shifts, and cycloadditions). In contrast to knowledge-based reaction mechanism prediction methods, the same kinetic heuristics are successful in classifying reaction pathways as feasible or infeasible across this diverse set of reaction mechanisms. We discuss the energy profiles of HAQC and their potential applications in machine learning of chemical reactivity.<br>

Predicting Feasible Organic Reaction Pathways Using Heuristically Aided Quantum Chemistry

2018 ◽  
Author(s):  
Dmitrij Rappoport ◽  
Alan Aspuru-Guzik
Keyword(s):  
Quantum Chemistry ◽  
Reaction Mechanisms ◽  
Quantum Chemical ◽  
Organic Reactions ◽  
Reaction Pathways ◽  
Empirical Knowledge ◽  
Organic Reaction ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Wide Range

Studying organic reaction mechanisms using quantum chemical methods requires from the researcher an extensive knowledge of both organic chemistry and first-principles computation. The need for empirical knowledge arises because any reasonably complete exploration of the potential energy surfaces (PES) of organic reactions is computationally prohibitive. We have previously introduced the Heuristically-Aided Quantum Chemistry (HAQC) approach to modeling complex chemical reactions, which abstracts the empirical knowledge in terms of chemical heuristics—simple rules guiding the PES exploration—and combines them with structure optimizations using quantum chemical methods. The HAQC approach makes use of heuristic kinetic criteria for selecting reaction paths that are not only plausible, that is, consistent with the empirical rules of organic reactivity, but also feasible under the reaction conditions. In this work, we develop heuristic kinetic feasilibity criteria, which correctly predict feasible reaction pathways for a wide range of simple polar (substitutions, additions, and eliminations) and pericyclic organic reactions (cyclizations, sigmatropic shifts, and cycloadditions). In contrast to knowledge-based reaction mechanism prediction methods, the same kinetic heuristics are successful in classifying reaction pathways as feasible or infeasible across this diverse set of reaction mechanisms. We discuss the energy profiles of HAQC and their potential applications in machine learning of chemical reactivity.<br>

scholarly journals Thinking like an electron: concepts pertinent to developing proficiency in organic reaction mechanisms

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Sachin Nedungadi ◽  
Corina E. Brown
Keyword(s):  
Organic Chemistry ◽  
Reaction Mechanisms ◽  
Large Scale ◽  
Phase 1 ◽  
Concept Inventory ◽  
Organic Reaction ◽  
General Consensus ◽  
Large Scale Assessment ◽  
Future Work ◽  
Organic Reaction Mechanisms

AbstractThe difficulties students face with organic reaction mechanisms have been the subject of much research in chemical education however, no concept inventory has been reported in this area. The development of a concept inventory would be useful for the large-scale assessment of students’ understanding of concepts pertinent to developing proficiency in reaction mechanisms. The first step in the design of such an inventory is identifying the pertinent concepts. In phase 1 of this study, open-ended interviews were carried out with organic chemistry instructors (N = 11) in order to ascertain their opinions on pertinent concepts for developing proficiency in reaction mechanisms. Phase 2 of the study consisted of a national survey of organic chemistry instructors (N = 183) to explore the general consensus regarding the concepts identified in phase 1. The results yielded 10 concepts identified by experts to be pertinent to reaction mechanisms. The general consensus among organic chemistry instructors is that the topic of reaction mechanisms is important to the study of organic chemistry, but students have difficulty understanding the meaning of the curved-arrow notation. Future work will include the design and development of a concept inventory based on these pertinent concepts.

scholarly journals Investigating students understanding of organic reaction mechanisms from performing organic chemistry experiments

2020 ◽  
Author(s):  
Nimesh Mistry ◽  
Stephen Nicholson
Keyword(s):  
Organic Chemistry ◽  
Reaction Mechanisms ◽  
Practical Work ◽  
Laboratory Work ◽  
Scientific Concepts ◽  
Organic Reaction ◽  
Student Reflections ◽  
Organic Reaction Mechanisms

The use of laboratory work to improve students’ knowledge of theory is one that is disputed. Student reflections of what they learn during practical work repeatedly show that students rarely think about theory. There is a lack of data that objectively compares students’ knowledge of theory where they complete an associated experiment to when they do not in order to understand if practical work does effect students’ knowledge of scientific concepts. In this work we aimed to address this gap by investigating the effect of students’ knowledge of organic mechanisms where they both perform and associated experiment and where they did not. Our results showed that organic chemistry experiments had no effect on students’ knowledge of organic mechanisms. These results support the view that there is little evidence to support the use of laboratory work to aid understanding of theory.

Microemulsions as microreactors in physical organic chemistry

2007 ◽  
Vol 79 (6) ◽  
pp. 1111-1123 ◽  
Author(s):  
Luis García-Río ◽  
J. Ramon Leis ◽  
Juan Carlos Mejuto ◽  
Moisés Pérez-Lorenzo
Keyword(s):  
Organic Chemistry ◽  
Organic Molecules ◽  
Reaction Rates ◽  
Organic Reactions ◽  
Water Interface ◽  
Physical Organic Chemistry ◽  
Organic Reaction ◽  
Physical Organic ◽  
Oil Water ◽  
Reaction Media

Microemulsions are very versatile reaction media which nowadays find many applications, ranging from nanoparticle templating to preparative organic chemistry. The thermodynamically stable and microheterogeneous nature of microemulsions, used as reaction media, induces drastic changes in the reagent concentrations, and this can be specifically used for tuning the reaction rates. In particular, amphiphilic organic molecules can accumulate and orient at the oil-water interface, inducing regiospecificity in organic reactions. In this review, we will show the recent tendencies of the use of microemulsions as organic reaction media.

Scientific genealogies of physical and mechanistic organic chemists

2005 ◽  
Vol 83 (9) ◽  
pp. 1400-1414 ◽  
Author(s):  
John Andraos
Keyword(s):  
Organic Chemistry ◽  
Career Development ◽  
Reaction Mechanisms ◽  
Research Council ◽  
National Research Council ◽  
Physical Organic Chemistry ◽  
Organic Reaction ◽  
Canadian Universities ◽  
Physical Organic ◽  
Scientific Ideas

Scientific genealogy trees of scientists who contributed to the study of organic reaction mechanisms over the last century are presented. The trees show doctoral and post-doctoral connections among scientists as well as connections between scientific ideas. Contributions made by scientists working in laboratories at Canadian universities and at the National Research Council of Canada are noted throughout. These trees, covering more than two centuries, are of interest to senior scientists and young students of science alike in understanding the evolution of scientific ideas and in career development for aspiring scientists. Key patterns revealed by these trees pertaining to ideas and discoveries made, how they were made, connections between them, and who made them are also discussed.Key words: reaction mechanisms, physical organic chemistry, scientific genealogies.

What students write about when students write about mechanisms: analysis of features present in students’ written descriptions of an organic reaction mechanism

2020 ◽  
Vol 21 (4) ◽  
pp. 1148-1172
Author(s):  
Field M. Watts ◽  
Jennifer A. Schmidt-McCormack ◽  
Catherine A. Wilhelm ◽  
Ashley Karlin ◽  
Atia Sattar ◽  
...  
Keyword(s):  
Organic Chemistry ◽  
Reaction Mechanisms ◽  
Conceptual Knowledge ◽  
Empirical Support ◽  
Qualitative Description ◽  
Chemistry Laboratory ◽  
Science Literature ◽  
Organic Reaction ◽  
Mechanistic Reasoning ◽  
Written Descriptions

Learning to reason through organic reaction mechanisms is challenging for students because of the volume of reactions covered in introductory organic chemistry and the complexity of conceptual knowledge and reasoning skills required to develop meaningful understanding. However, understanding reaction mechanisms is valuable for students because they are useful for predicting and explaining reaction outcomes. To identify the features students find pertinent when explaining reaction mechanisms, we have collected students’ written descriptions of an acid-catalysed amide hydrolysis reaction. Students’ writing was produced during the implementation of Writing-to-Learn assignments in a second semester organic chemistry laboratory course. We analysed students’ written responses using an analytical framework for recognizing students’ mechanistic reasoning, originally developed with attention to the philosophy of science literature. The analysis sought to identify the presence of specific features necessary for mechanistic reasoning belonging to four broad categories: (1) describing an overview of the reaction, (2) detailing the setup conditions required for the mechanism to occur, (3) describing the changes that take place over the course of the mechanism, and (4) identifying the properties of reacting species. This work provides a qualitative description of the variety of ways in which students included these features necessary for mechanistic reasoning in their writing. We additionally analysed instances of co-occurrence for these features in students’ writing to make inferences about students’ mechanistic reasoning, defined here as the use of chemical properties to justify how electrons, atoms, and molecules are reorganized over the course of a reaction. Feature co-occurrences were quantified using the lift metric to measure the degree of their mutual dependence. The quantitative lift results provide empirical support for the hierarchical nature of students’ mechanistic descriptions and indicate the variation in students’ descriptions of mechanistic change in conjunction with appeals to chemistry concepts. This research applies a framework for identifying the features present in students’ written mechanistic descriptions, and illustrates the use of an association metric to make inferences about students’ mechanistic reasoning. The findings reveal the capacity of implementing and analysing writing to make inferences about students’ mechanistic reasoning.

scholarly journals Exploring the Perception of Chemistry Students at Kulliyyah of Science in Learning Organic Chemistry

2021 ◽  
Vol 9 (2) ◽  
pp. 6-30
Author(s):  
Nurul Nadiah Rosly ◽  
Shafida Abd Hamid ◽  
Nor Azlina A. Rahman
Keyword(s):  
Organic Chemistry ◽  
Reaction Mechanisms ◽  
Difficulty Level ◽  
Teaching Approaches ◽  
High Failure Rate ◽  
Organic Reaction ◽  
Reaction Type ◽  
Chemistry Students

Students perceive organic chemistry as a challenging subject for them to learn and master, which results in a high failure rate. This study investigates the perception of chemistry students of the Department of Chemistry, Kulliyyah of Science at International Islamic University Malaysia (IIUM), on organic chemistry courses and identify the topics that the students found difficult to grasp, which may affect their grades. The correlation of students’ perception on the difficulty level in studying organic chemistry subjects (I and II) with the grades obtained for both courses, and the correlation of the type of study attitude with the grades achieved for Organic Chemistry I and II, were also investigated. From the data analysis of questionnaires distributed to 160 respondents, stereochemistry (n = 58.8 %), determination of reaction type (n = 59.4 %), construction of the reaction mechanisms (n = 73.2 %), and characterisation of organic reaction (n = 77.5 %), were the topics that the students perceived to be difficult. Perception on the difficulty in studying organic chemistry was positively associated with the achievement of excellent grades for both organic chemistry subjects (I; rs = 0.413**, p<0.01 and II; rs = 0.436**, p<0.01). Quality of study attitude shows no association with the grades obtained for organic chemistry I (rs = 0.330**, p = 1.00) but positively associated with grades of organic chemistry II subject (rs = 0.140, p<0.01). This study could serve as a reference for lecturers to search for ways to design appropriate teaching approaches for better learning experiences.

scholarly journals A roma képzőművészet korunk modernitásának kontextusában

2018 ◽  
Vol 30 (3) ◽  
pp. 92-104
Author(s):  
Barbara Illés
Keyword(s):  
Fine Arts ◽  
Fine Art ◽  
Detailed Knowledge ◽  
Processes Of Change ◽  
Short History ◽  
Art Scene ◽  
Ethnic Classification ◽  
Set Up ◽  
Definition Of

The objective of the current paper is defining of the notion of fine art of the Roma minority with an overview of its short history as for the largest population of ethnicity who more than six centuries living in Hungary. Apart from the definition of Roma Art, I am discussing the processes of change and the self-representation of the present, mainly from the aspect of the artist, the ethnic classification of Roma identity through self-confessions. I set up the Roma Art scene based on traditions, then the Modern Hungarian-Roma Fine Arts that emerged from it, and finally define the categories of Professional Fine Art in relation to each other and to their association with Hungarian Fine Art and European Gypsy Art and Universal Art. Apart from the interpretation of Roma Art, the study offers an opportunity for contemporary artists to get more accurate and detailed knowledge and to understand and evaluate their works more closely and sophisticated.

scholarly journals Utilizing Rasch analysis to establish the psychometric properties of a concept inventory on concepts important for developing proficiency in organic reaction mechanisms

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Sachin Nedungadi ◽  
Sue H. Paek ◽  
Corina E. Brown
Keyword(s):  
Organic Chemistry ◽  
Reaction Mechanisms ◽  
Rasch Analysis ◽  
Large Scale ◽  
Assessment Tool ◽  
Validity And Reliability ◽  
Organic Reaction ◽  
First Semester ◽  
Chemistry Students ◽  
Organic Reaction Mechanisms

AbstractUndergraduate organic chemistry has been found to be historically difficult for students and one area where students struggle is organic reaction mechanisms. The difficulties students face with reaction mechanisms has been a source of interest in chemical education research but most studies done have been purely qualitative. An assessment tool that could be used on a large-scale for instructors to gauge the difficulties their students face, would be useful. The aim of this pilot study is to use Rasch analysis to establish the validity and reliability of the concepts important for developing proficiency in organic reaction mechanisms inventory (RMCPI). The test, containing 25 items, was administered to first semester organic chemistry students (N = 44) at a mid-sized university. The data was analyzed using Rasch techniques to explore the dimensionality of the instrument, the difficulty of the items, the item fit, and the reliability. The results indicate that the instrument is unidimensional and most of the items fit well to the dichotomous Rasch model. The test was found to be difficult and this will be explored further by increasing the sample size, administering the test to students from other universities and increasing the number of items on the inventory.

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