From strong to weak NF bonds: on the design of a new class of fluorinating agents

2018 ◽  
Vol 20 (37) ◽  
pp. 23913-23927 ◽  
Author(s):  
Dani Setiawan ◽  
Daniel Sethio ◽  
Dieter Cremer ◽  
Elfi Kraka
Keyword(s):  
Bond Strength ◽  
Quantitative Description ◽  
Force Constants ◽  
New Class ◽  
Strength Based

The first quantitative description of the NF bond strength based on local vibrational stretching NF force constants determined with CCSD(T).

The intrinsic strength of the halogen bond: electrostatic and covalent contributions described by coupled cluster theory

2016 ◽  
Vol 18 (48) ◽  
pp. 33031-33046 ◽  
Author(s):  
Vytor Oliveira ◽  
Elfi Kraka ◽  
Dieter Cremer
Keyword(s):  
Bond Strength ◽  
Halogen Bond ◽  
Quantitative Description ◽  
Force Constants ◽  
Coupled Cluster ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Strength Based ◽  
Intrinsic Strength

The first quantitative description of the halogen bond strength based on local vibrational stretching force constants determined with CCSD(T).

scholarly journals Exceptionally Long Covalent CC Bonds—A Local Vibrational Mode Study

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 950
Author(s):  
Alexis Antoinette Ann Delgado ◽  
Alan Humason ◽  
Robert Kalescky ◽  
Marek Freindorf ◽  
Elfi Kraka
Keyword(s):  
Bond Strength ◽  
Radical Cation ◽  
Steric Hindrance ◽  
Force Constants ◽  
Electronic Effects ◽  
Future Design ◽  
Local Vibrational Mode ◽  
Negative Hyperconjugation ◽  
New Guidelines ◽  
First Time

For decades one has strived to synthesize a compound with the longest covalent C−C bond applying predominantly steric hindrance and/or strain to achieve this goal. On the other hand electronic effects have been added to the repertoire, such as realized in the electron deficient ethane radical cation in its D3d form. Recently, negative hyperconjugation effects occurring in diamino-o-carborane analogs such as di-N,N-dimethylamino-o-carborane have been held responsible for their long C−C bonds. In this work we systematically analyzed CC bonding in a diverse set of 53 molecules including clamped bonds, highly sterically strained complexes such as diamondoid dimers, electron deficient species, and di-N,N-dimethylamino-o-carborane to cover the whole spectrum of possibilities for elongating a covalent C−C bond to the limit. As a quantitative intrinsic bond strength measure, we utilized local vibrational CC stretching force constants ka(CC) and related bond strength orders BSO n(CC), computed at the ωB97X-D/aug-cc-pVTZ level of theory. Our systematic study quantifies for the first time that whereas steric hindrance and/or strain definitely elongate a C−C bond, electronic effects can lead to even longer and weaker C−C bonds. Within our set of molecules the electron deficient ethane radical cation, in D3d symmetry, acquires the longest C−C bond with a length of 1.935 Å followed by di-N,N-dimethylamino-o-carborane with a bond length of 1.930 Å. However, the C−C bond in di-N,N-dimethylamino-o-carborane is the weakest with a BSO n value of 0.209 compared to 0.286 for the ethane radical cation; another example that the longer bond is not always the weaker bond. Based on our findings we provide new guidelines for the general characterization of CC bonds based on local vibrational CC stretching force constants and for future design of compounds with long C−C bonds.

scholarly journals Evaluation and Comparison of Shear Bond Strengths of Self Etching Primers To Dentin– an In-Vitro Study

2014 ◽  
Vol 02 (02) ◽  
pp. 091-095
Author(s):  
Veerendra Uppin ◽  
Priyanka Sarangi ◽  
Sukanta Satapathy
Keyword(s):  
Shear Strength ◽  
Bond Strength ◽  
Shear Bond Strength ◽  
Testing Machine ◽  
In Vitro Study ◽  
Strength Based ◽  
Molar Teeth ◽  
Bond Strengths ◽  
Abrasive Paper

AbstractAn in-vitro evaluation was done to compare shear bond strength of four self etching primer adhesives to dentin. 75 human extracted molar teeth were selected. The occlusal surface of these teeth was ground to remove coronal enamel and expose dentin. The dentinal surface of each tooth was then abraded using series of silicon carbide (320, 400, 600 grit) abrasive paper. Teeth were divided into 5 groups of 15 teeth each and composite post were then built on the bonded surfaces using Z-100 hybrid composite. The teeth were then fractured applying shearing load through universal testing machine. Shear strength values were in the range of 15.96 to 22.64 Mpa. Clearfil S3 gave highest mean shear bond strength whereasAdhe SE gave lowest value of shear strength. Based on this study it could be concluded that contemporary self etching primer adhesives bond successfully to dentin and also their bonding ability seems to be comparable to conventional total etch system.

scholarly journals Bond Strength of Fusion Bonded Epoxy-Coated Reinforcement in Concrete

2019 ◽  
Vol 5 (3) ◽  
pp. 255
Author(s):  
G M Sadiqul Islam ◽  
Ehsan Ahmed ◽  
Md. Sabbir Hossain ◽  
S. M. Sharif Uddin
Keyword(s):  
Bond Strength ◽  
Concrete Strength ◽  
Epoxy Coating ◽  
Test Results ◽  
Reinforced Concrete Structure ◽  
Reinforcing Bars ◽  
Strength Based ◽  
Modification Factor ◽  
Bar Diameter ◽  
Bond Characteristics

Fusion-bonded epoxy-coated steel is expected to extend the service life of the reinforced concrete structure in chloride-laden environments. However, the effect of coating on the bond-strength between rebar and concrete is not well understood yet. This research, therefore, studied the effect of epoxy-coating on the bond characteristics of reinforcing bars in concrete. The bond characteristics were assessed through pullout test considering variables viz. concrete strength, embedded length and bar diameter. The load was applied to reinforcing bars embedded in concrete until bond strength between the bar and concrete exceeded. Bond strength of epoxy-coated bars was compared with that of the uncoated bars. It was found that epoxy-coating reduced the bond strength approximately 25% for Ø20mm bar and 12% for Ø16mm and Ø12mm bar. As with uncoated bar, bond strength of coated bars were also increased with concrete strength. However, the bond strength ratio between coated and uncoated bars was found almost independent of concrete strength. Based on the test results, a development length modification factor of 1.33 is proposed for Ø20mm bar and 1.15 for Ø12mm and Ø16mm bar to compensate the bond strength reduction due to the epoxy coating.

Quantification of Hydrogen Bond Strength Based on Interaction Coordinates: A New Approach

2017 ◽  
Vol 121 (32) ◽  
pp. 6090-6103 ◽  
Author(s):  
Sarvesh Kumar Pandey ◽  
Dhivya Manogaran ◽  
Sadasivam Manogaran ◽  
Henry F. Schaefer
Keyword(s):  
Hydrogen Bond ◽  
Bond Strength ◽  
New Approach ◽  
Hydrogen Bond Strength ◽  
Strength Based

Schwingungseigenschaften des PO43-Ions im Monazit-und Zirkon-Gitter

1982 ◽  
Vol 37 (4) ◽  
pp. 380-382 ◽  
Author(s):  
Enrique J. Baran ◽  
Araceli E. Lavat
Keyword(s):  
Rare Earth ◽  
Bond Strength ◽  
Structural Type ◽  
Unit Cell ◽  
Force Constants ◽  
Cell Contraction ◽  
Mean Amplitudes Of Vibration ◽  
The Rare Earth

Abstract The force constants and mean amplitudes of vibration for the PO43- ion present in the lattices of the rare earth orthophosphates of the monazite and zircon types, have been calculated from recently reported Raman data. It is shown that the P-O bond strength depends not only on the overall unit cell contraction but also on the structural type.

scholarly journals III-defined concepts in chemistry: rigid force constants vs. compliance constants as bond strength descriptors for the triple bond in diboryne

2015 ◽  
Vol 6 (7) ◽  
pp. 4086-4088 ◽  
Author(s):  
Jörg Grunenberg
Keyword(s):  
Bond Strength ◽  
Triple Bond ◽  
Force Constants ◽  
Compliance Constants

In a recent publication in this journal, the interpretation of the Braunschweig's diboryne as a true triple bond is questioned.

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