scholarly journals Substituent effects on the basicity (pKa) of aryl guanidines and 2-(arylimino)imidazolidines: correlations of pH-metric and UV-metric values with predictions from gas-phase ab initio bond lengths

2017 ◽  
Vol 41 (19) ◽  
pp. 11016-11028 ◽  
Author(s):  
Christophe Dardonville ◽  
Beth A. Caine ◽  
Marta Navarro de la Fuente ◽  
Guillermo Martín Herranz ◽  
Beatriz Corrales Mariblanca ◽  
...  
Keyword(s):  
Ab Initio ◽  
Bond Length ◽  
Gas Phase ◽  
Substituent Effects ◽  
Bond Lengths

The AIBLHiCoS method accurately predicts the pKa values of 2-(arylimino)imidazolidines using only a single ab initio bond length.

Correction: Substituent effects on the basicity (pKa) of aryl guanidines and 2-(arylimino)imidazolidines: correlations of pH-metric and UV-metric values with predictions from gas-phase ab initio bond lengths

2017 ◽  
Vol 41 (19) ◽  
pp. 11423-11423
Author(s):  
Christophe Dardonville ◽  
Beth A. Caine ◽  
Marta Navarro de la Fuente ◽  
Guillermo Martín Herranz ◽  
Beatriz Corrales Mariblanca ◽  
...  
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Substituent Effects ◽  
Bond Lengths

Correction for ‘Substituent effects on the basicity (pKa) of aryl guanidines and 2-(arylimino)imidazolidines: correlations of pH-metric and UV-metric values with predictions from gas-phase ab initio bond lengths’ by Christophe Dardonville et al., New J. Chem., 2017, DOI: 10.1039/c7nj02497e.

Bond order-bond length relationships in conjugated hydrocarbons - the microwave spectrum and structure of 3,4-dimethylenecyclobutene

1983 ◽  
Vol 36 (4) ◽  
pp. 639 ◽  
Author(s):  
RD Brown ◽  
PD Godfry ◽  
BT Hart ◽  
AL Ottrey ◽  
M Onda ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Ab Initio ◽  
Bond Length ◽  
Bond Order ◽  
Microwave Spectrum ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Bond Orders ◽  
Bond Lengths ◽  
Typical Error

The microwave spectrum of the benzene isomer 3,4-dimethylenecyclobutene including spectra of all possible single 13C-substituted and sufficient singly and doubly D-substituted species to give a complete r5 geometry, have been measured and analysed. An estimate of the re geometry has also been derived. The additional precise CC bond lengths obtained for an unsubstituted, conjugated hydrocarbon enable us to examine bond order-bond length relationships more thoroughly than has previously been possible. The CC bond lengths exhibit a noticeably better correlation with SCFMO bond orders than with simple H�ckel bond orders. Further confirmatory measurements of the dipole moment of dimethylenecyclobutene have been made. Ab initio molecular orbital calculations using a 6-31G basis set give an optimized geometry with CC bond lengths within 2 pm of the r5 values. The computed dipole moment agrees almost exactly with experiment but a corresponding calculation on fulvene is discrepant with experiment by 0.16 D, which is probably a more typical error.

The polyoctahedral silsesquioxane (POSS) 1,3,5,7,9,11,13,15-octaphenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (octaphenyl-POSS)

2014 ◽  
Vol 70 (10) ◽  
pp. 971-974 ◽  
Author(s):  
Parameswara Rao Chinnam ◽  
Michael R. Gau ◽  
Joseph Schwab ◽  
Michael J. Zdilla ◽  
Stephanie L. Wunder
Keyword(s):  
Single Crystal ◽  
Bond Length ◽  
Single Crystals ◽  
Gas Phase ◽  
Solvent Free ◽  
Powder Pattern ◽  
Crystal Data ◽  
Bond Angles ◽  
Bond Lengths ◽  
Centrosymmetric Molecule

Solvent-free single crystals of 1,3,5,7,9,11,13,15-octaphenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (abbreviated as octaphenyl-POSS), C48H40O12Si8, were obtained by dehydration/condensation of the tetrol Si4O4(Ph)4(OH)4. The powder pattern generated from the single-crystal data matches well with the experimentally measured powder pattern of commercial octaphenyl-POSS. The geometry of the centrosymmetric molecule in the crystal was compared with that in the gas phase, and had shorter Si—O bond lengths and a broader range of Si—O—Si bond angles. The average Si—O bond length [1.621 (3) Å], and Si—O—Si and O—Si—O bond angles [149 (5) and 109 (1)°, respectively] were within the same range measured previously for octaphenyl-POSS solvates.

scholarly journals Syntheses and Structures of Novel λ3,λ3-Phosphanylalumanes Fully Bearing Carbon Substituents and Their Substituent Effects

Inorganics ◽  
2019 ◽  
Vol 7 (11) ◽  
pp. 132 ◽  
Author(s):  
Tatsuya Yanagisawa ◽  
Yoshiyuki Mizuhata ◽  
Norihiro Tokitoh
Keyword(s):  
Bond Length ◽  
Theoretical Calculations ◽  
Substituent Effects ◽  
The Other ◽  
Protecting Groups ◽  
Large Contribution ◽  
The Novel ◽  
Single Bond ◽  
Bond Lengths ◽  
Theoretical Results

The novel phosphanylalumanes, Al–P single-bond species, fully bearing carbon protecting groups on aluminum and phosphorus atoms, are synthesized by the reactions of aluminum monohalides [(t-Bu)2AlBr and (C6F5)2AlCl·0.5(toluene)] with Mes2PLi. Regarding the t-Bu system, λ3,λ3-phosphanylalumane is obtained. Concerning the C6F5 system, on the other hand, the corresponding LiCl complex, λ4,λ4-phosphanylalumane, is obtained. The Al–P bond lengths of C6F5-substituted λ3,λ4-, and λ4,λ4-derivatives are much shorter than those of the reported λ3,λ4-phosphanylalumane derivatives and comparable to that observed for the previously reported λ3,λ3-phosphanylalumanes. Theoretical calculations reveal that the binding of the C6F5 groups to Al results in a large contribution of Al and a large s-character in the Al–P bond of phosphanylalumanes. Considering t-Bu-substituted phosphanylalumanes, the Al–P bond lengths reflect the coordination number of Al, showing a longer Al–P bond length in the case of λ4-Al as compared with that of λ3-Al. Combining the structural, spectroscopic, and theoretical results, the t-Bu-substituted λ3,λ3-phosphanylalumane has well separated vacant p orbital and lone pairs, which is suitable for reactivity studies.

Predicting pK a Values in Aqueous Solution for the Guanidine Functional Group from Gas Phase Ab Initio Bond Lengths

2013 ◽  
Vol 32 (4) ◽  
pp. 363-376 ◽  
Author(s):  
Mark Z. Griffiths ◽  
Ibon Alkorta ◽  
Paul L. A. Popelier
Keyword(s):  
Aqueous Solution ◽  
Ab Initio ◽  
Gas Phase ◽  
Functional Group ◽  
Bond Lengths

Semiempirical and ab initio study of the nature of the C-S bond in sulfonium ylides

1981 ◽  
Vol 46 (4) ◽  
pp. 883-891 ◽  
Author(s):  
Vladimír Král ◽  
Zdeněk Arnold ◽  
Zdeněk Havlas
Keyword(s):  
Total Energy ◽  
Ab Initio ◽  
Bond Length ◽  
Satisfactory Agreement ◽  
Basis Set ◽  
Charge Reduction ◽  
Ab Initio Study ◽  
High Quality ◽  
Bond Lengths ◽  
Sulfonium Ylides

The importance of d-orbitals for the interpretation of properties of sulfonium ylides is demonstrated on the basis of semiempirical and ab initio calculations. The calculated C-S bond length values are sensitive to inclusion of d-orbitals into the AO basis set. Even a high quality basis (4-31 G) without d-orbitals leads to C-S bond lengths which are significantly larger than the experimental ones whereas bases including d-orbitals afford satisfactory agreement. Inclusion of d-orbitals results in charge reduction on the atoms C and S and in a substantially increased order of the bond between these atoms. The decrease of total energy which results from inclusion of d-orbitals is related to (d-p)π bonding overlap between the atoms S and C.

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