Gauging the Donor Ability of the C-Si Bond. Results from Low-Temperature Structural Studies of gauche and Antiperiplanar β-Trimethylsilyl-cyclohexyl Esters and Ethers by Use of the Variable Oxygen Probe.

2000 ◽  
Vol 53 (4) ◽  
pp. 285 ◽  
Author(s):  
Alison J. Green ◽  
Josie Giordano ◽  
Jonathan M. White
Keyword(s):  
Low Temperature ◽  
Bond Distance ◽  
Structural Studies ◽  
Oxygen Probe ◽  
Pka Value ◽  
Donor Ability ◽  
Derivatives Of

A plot of C–OR bond distance against pKa(ROH) for esters and ether derivatives of the antiperiplanar β-silyl alcohol (4) has a slope of –5.310–3. This represents a stronger response of the C–OR distance than was observed for the corresponding gauche β-silyl alcohol (5) and its derivatives. This result is consistent with the greater donor ability of a C–Si bond compared with a C–C bond. Comparison of these plots with those previously reported for derivatives (3) of tetrahydropyran-2-ol reveals that a C–Si bond is a weaker donor than an oxygen non-bonded pair of electrons. An estimate of the pKa value for 2,4-dinitrobenzenesulfenic acid (14) was derived from these plots.

Application of the Variable Oxygen Probe to Determine the π-Electron Donor Ability of the Alkyne Group

2014 ◽  
Vol 67 (12) ◽  
pp. 1866 ◽  
Author(s):  
Benjamin L. Harris ◽  
Jonathan M. White
Keyword(s):  
Low Temperature ◽  
Electron Donor ◽  
Oxygen Probe ◽  
X Ray ◽  
X Ray Crystallography ◽  
Donor Ability ◽  
Structural Database ◽  
Derivatives Of ◽  
Electron Demand ◽  
Electron Donor Ability

Eight ester and ether derivatives of propargyl alcohol with varying electron demand were structurally characterised using low temperature X-ray crystallography, these were combined with seven derivatives obtained from the Cambridge Structural Database. Variable oxygen probe analysis of these derivatives provided evidence that the ethynyl substituent is a relatively weak π-electron donor, and is a slightly less effective donor than the C–C bond of an ethyl substituent.

The Through-Bond Interaction of a Sulfur Lone Pair with Oxygenated Substituents in the Thiacyclohexane Framework

2005 ◽  
Vol 58 (7) ◽  
pp. 531
Author(s):  
Laura Andrau ◽  
Jonathan M. White
Keyword(s):  
Low Temperature ◽  
Crystal Structures ◽  
Bond Distance ◽  
Lone Pair ◽  
X Ray ◽  
Ester Derivative ◽  
Bond Interaction ◽  
Derivatives Of ◽  
Electron Demand

Low-temperature X-ray crystal structures were determined on a range of derivatives of 4-thiacyclohexanol 5a of varying electron demand with a view to finding evidence for a through-bond interaction between the sulfur lone pair and the oxygenated substituent. In contrast to earlier suggestions, plots of C–OR bond distance versus pKa (ROH) showed that any interaction between the sulfur and the OR group is unlikely to be of a through-bond origin. Furthermore, unimolecular solvolysis rate measurements on the nosylate ester derivative 5g showed that the sulfur actually retards the reaction slightly in comparison with the corresponding sulfur-free analogue 6.

Synthesis, Structural Studies and Biological Evaluation of Halogen Derivatives of 1,3-Disubstituted Thiourea

2017 ◽  
Vol 14 (6) ◽  
Author(s):  
Anna Bielenica ◽  
Karolina Stepien ◽  
Aleksandra Sawczenko ◽  
Tadeusz Lis ◽  
Anna E. Koziol ◽  
...  
Keyword(s):  
Biological Evaluation ◽  
Structural Studies ◽  
Derivatives Of

scholarly journals High-pressure, low-temperature structural studies of orientationally ordered C60

1993 ◽  
Vol 5 (43) ◽  
pp. 7923-7928 ◽  
Author(s):  
W I F David ◽  
R M Ibberson
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Structural Studies

Derivatives of isatin in aqueous solution. I. Kinetics of ring opening of Isatin-5-sulfonate

1981 ◽  
Vol 34 (2) ◽  
pp. 365 ◽  
Author(s):  
H Stunzi
Keyword(s):  
Ring Opening ◽  
Rate Of Change ◽  
Spectroscopic Methods ◽  
Ph Values ◽  
Buffer Region ◽  
Pka Value ◽  
Back Titration ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Sulfonate Anion

The reactions of isatin-5-sulfonate anion (si-) which cause a hysteresis in pH titrations were studied by pH-metric and n.m.r, spectroscopic methods. Rapid alkalimetric titrations [I 0.15 M (KNO3),37�] gave the pKa value corresponding to the addition of OH- to si- [pKa(ring) 9.55]. The slow ring opening to the sulfonatoisatate dianion (sia2-) led to a drift of the pH values towards an equilibrium buffer region. Its pKa, value [pKa(eq) 3.44] corresponds to the reaction si-+H2O ↔ sia 2-+H+ Rapid back-titration gave the pKa value of the ring-opened species Hsia- [pKa(open) c. 1.3]. The rate law for the ring opening d[sia]/dt=k2 [siOH](OH)+k1*[si] was obtained from the rate of change of pH. N-Methylisatin-5-sulfonate behaves analogously.

Low temperature structural studies of SrSnO3

2015 ◽  
Vol 27 (36) ◽  
pp. 365401 ◽  
Author(s):  
Brendan J Kennedy ◽  
Ilyas Qasim ◽  
Kevin S Knight
Keyword(s):  
Low Temperature ◽  
Structural Studies

Synthesis, structural studies and biological activity of novel Cu(II) complexes with thiourea derivatives of 4-azatricyclo[5.2.1.0 2,6 ]dec-8-ene-3,5-dione

2017 ◽  
Vol 176 ◽  
pp. 8-16 ◽  
Author(s):  
Aleksandra Drzewiecka-Antonik ◽  
Paweł Rejmak ◽  
Marcin T. Klepka ◽  
Anna Wolska ◽  
Piotr Pietrzyk ◽  
...  
Keyword(s):  
Biological Activity ◽  
Structural Studies ◽  
Thiourea Derivatives ◽  
Derivatives Of
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