A theoretical treatment of nucleophilic reactivity in additions to carbonyl compounds. Role of the vertical ionization energy

1988 ◽  
Vol 110 (4) ◽  
pp. 1275-1279 ◽  
Author(s):  
Erwin. Buncel ◽  
Sason S. Shaik ◽  
Ik Hwan. Um ◽  
Saul. Wolfe
Keyword(s):  
Ionization Energy ◽  
Carbonyl Compounds ◽  
Theoretical Treatment ◽  
Vertical Ionization Energy ◽  
Nucleophilic Reactivity

scholarly journals Robust and efficient hydrogenation of carbonyl compounds catalysed by mixed donor Mn(I) pincer complexes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wenjun Yang ◽  
Ivan Yu. Chernyshov ◽  
Robin K. A. van Schendel ◽  
Manuela Weber ◽  
Christian Müller ◽  
...  
Keyword(s):  
Noble Metal ◽  
Crucial Role ◽  
Carbonyl Compounds ◽  
Catalytic Performance ◽  
Hydrogen Atmosphere ◽  
Pincer Complexes ◽  
Catalyst Activation ◽  
Hydrogenation Catalysts ◽  
Induction Times

AbstractAny catalyst should be efficient and stable to be implemented in practice. This requirement is particularly valid for manganese hydrogenation catalysts. While representing a more sustainable alternative to conventional noble metal-based systems, manganese hydrogenation catalysts are prone to degrade under catalytic conditions once operation temperatures are high. Herein, we report a highly efficient Mn(I)-CNP pre-catalyst which gives rise to the excellent productivity (TOF° up to 41 000 h−1) and stability (TON up to 200 000) in hydrogenation catalysis. This system enables near-quantitative hydrogenation of ketones, imines, aldehydes and formate esters at the catalyst loadings as low as 5–200 p.p.m. Our analysis points to the crucial role of the catalyst activation step for the catalytic performance and stability of the system. While conventional activation employing alkoxide bases can ultimately provide catalytically competent species under hydrogen atmosphere, activation of Mn(I) pre-catalyst with hydride donor promoters, e.g. KHBEt3, dramatically improves catalytic performance of the system and eliminates induction times associated with slow catalyst activation.

An effective and efficient approach to p-type AlN by Be2:O codoping from first-principles calculations

2016 ◽  
Vol 30 (20) ◽  
pp. 1650257
Author(s):  
Meng Zhao ◽  
Wenjun Wang ◽  
Jun Wang ◽  
Junwei Yang ◽  
Weijie Hu ◽  
...  
Keyword(s):  
First Principles ◽  
Ionization Energy ◽  
Hole Concentration ◽  
Valence Band Maximum ◽  
First Principles Calculations ◽  
Mutual Compensation ◽  
Efficient Approach ◽  
P Type ◽  
Codoping Method

Various Be:O-codoped AlN crystals have been investigated via first-principles calculations to evaluate the role of the different combinations in effectively and efficiently inducing p-type carriers. It is found that the O atom is favored to bond with two Be atoms. The formed Be2:O complexes decrease the acceptor ionization energy to 0.11 eV, which is 0.16 eV lower than that of an isolated Be in AlN, implying that the hole concentration could probably be increased by 2–3 orders of magnitude. The electronic structure of Be2:O-codoped AlN shows that the lower ionization energy can be attributed to the interaction between Be and O. The Be–O complexes, despite failing to induce p-type carriers for the mutual compensation of Be and O, introduce new occupied states on the valence-band maximum (VBM) and hence the energy needed for the transition of electrons to the acceptor level is reduced. Thus, the Be2:O codoping method is expected to be an effective and efficient approach to realizing p-type AlN.

scholarly journals Central role of carbonyl compounds in atmospheric chemistry

2000 ◽  
Vol 105 (D15) ◽  
pp. 19771-19778 ◽  
Author(s):  
D. J. Lary ◽  
D. E. Shallcross
Keyword(s):  
Atmospheric Chemistry ◽  
Carbonyl Compounds

Simple, Mild and Efficient Thioacetalization and Transthioacetalization of Carbonyl Compounds and Deprotection of Thioacetals: Unique Role of Thiols in the Selectivity of Thioacetalization

Synthesis ◽  
2005 ◽  
Vol 2005 (02) ◽  
pp. 250-254 ◽  
Author(s):  
Biswanath Das ◽  
Ravirala Ramu ◽  
Majjigapu Ravinder Reddy ◽  
Gurram Mahender
Keyword(s):  
Carbonyl Compounds ◽  
Unique Role

Some applications of polarography for investigation of equlibria in aqueous solutions of organic compounds

2009 ◽  
Vol 74 (11-12) ◽  
pp. 1777-1789 ◽  
Author(s):  
Petr Zuman
Keyword(s):  
Aqueous Solutions ◽  
Organic Compounds ◽  
Carbonyl Compounds ◽  
Limiting Current ◽  
Nitroso Compounds ◽  
Primary Amines ◽  
Acid Base ◽  
Fast Reactions ◽  
Half Wave

There are two possibilities how to follow equilibria of organic compounds established in aqueous solutions using polarography: for very fast reactions, information can be obtained from shifts of half-wave potentials. For slowly established equilibria, the changes in the limiting current are followed. In both cases variation of the half-wave potentials or limiting currents with concentration of a reactant, present in excess, is followed. The types of reactions, which had been followed in this way, are as follows: hydration–dehydration equilibria, additions of hydroxide ion to carbonyl and nitroso compounds, the role of slowly established acid–base equilibria involving C-acids; further also reactions involving the addition of ammonia, primary amines, hydroxylamine, and hydrazine to carbonyl compounds.

Collusion between public procurers and suppliers in the context of japan’s public procurement: The role of the risks of “unsuccessful procurement”

2016 ◽  
Vol 16 (3) ◽  
pp. 291-311 ◽  
Author(s):  
Satoru Tanaka ◽  
Shuya Hayashi
Keyword(s):  
Case Studies ◽  
Public Procurement ◽  
Theoretical Treatment ◽  
Public Official ◽  
Experience Goods ◽  
Economic Forces ◽  
Bid Rigging

This paper examines the economic forces which may lead to government-assisted or -facilitated bid-rigging (kansei-dango) in public procurement in Japan, and considers their implications. A public official may often worry about situations where his/her procurement project will not be successfully implemented. Based on a simplified theoretical treatment and on case studies of kansei-dango, it is argued that the desire to avert the risk of unsuccessful procurement resulting from the "experience goods" status of procured goods and/or services may be one reason for bid-rigging. Based on this understanding of kansei-dango, we discuss some implications for policies to restrain this type of corruption.

Solvation effect on the vertical ionization energy of adenine‐thymine base pair: From microhydration to bulk

2019 ◽  
Vol 120 (6) ◽  
Author(s):  
Madhubani Mukherjee ◽  
Soumi Haldar ◽  
Achintya K. Dutta
Keyword(s):  
Base Pair ◽  
Ionization Energy ◽  
Solvation Effect ◽  
Vertical Ionization Energy ◽  
Adenine Thymine

scholarly journals Acrylamide Formation in Food: A Mechanistic Perspective

2005 ◽  
Vol 88 (1) ◽  
pp. 262-267 ◽  
Author(s):  
Varoujan A Yaylayan ◽  
Richard H Stadler
Keyword(s):  
Amino Acid ◽  
Carbonyl Compounds ◽  
Azomethine Ylide ◽  
Significant Progress ◽  
Acid Moiety ◽  
Sugar Moiety ◽  
Acrylamide Formation ◽  
Amino Acid Moiety ◽  
Strecker Aldehyde

Abstract Earliest reports on the origin of acrylamide in food have confirmed asparagine as the main amino acid responsible for its formation. Available evidence suggests that sugars and other carbonyl compounds play a specific role in the decarboxylation process of asparagine, a necessary step in the generation of acrylamide. It has been proposed that Schiff base intermediate formed between asparagine and the sugar provides a low energy alternative to the decarboxylation from the intact Amadori product through generation and decomposition of oxazolidin-5-one intermediate, leading to the formation of a relatively stable azomethine ylide. Literature data indicate the propensity of such protonated ylides to undergo irreversible 1,2-prototropic shift and produce, in this case, decarboxylated Schiff bases which can easily rearrange into E Decarboxylated Amadori products can either undergo the well known β-elimination process initiated by the sugar moiety to produce 3-aminopropanamide and 1-deoxyglucosone or undergo 1,2-elimination initiated by the amino acid moiety to directly generate acrylamide. On the other hand, the Schiff intermediate can either hydrolyze and release 3-aminopropanamide or similarly undergo amino acid initiated 1,2-elimination to directly form acrylamide. Other thermolytic pathways to acrylamide—considered marginal at this stage—via the Strecker aldehyde, acrolein, and acrylic acid, are also addressed. Despite significant progress in the understanding of the mechanistic aspects of acrylamide formation, concrete evidence for the role of the different proposed intermediates in foods is still lacking.

Efficient Role of Mg-ZnCl2 for Selective Reduction of α,β-Unsaturated Carbonyl Compounds in Aqueous Medium.

ChemInform ◽  
2005 ◽  
Vol 36 (29) ◽  
Author(s):  
Anil Saikia ◽  
Madan Gopal Barthakur ◽  
Romesh Chandra Boruah
Keyword(s):  
Aqueous Medium ◽  
Carbonyl Compounds ◽  
Selective Reduction
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