Oxidation potentials of carbanions and homolytic bond dissociation energies of their conjugate acids

1989 ◽  
Vol 54 (13) ◽  
pp. 3101-3105 ◽  
Author(s):  
Fred G. Bordwell ◽  
John A. Harrelson ◽  
Amruthur V. Satish
Keyword(s):  
Bond Dissociation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Oxidation Potentials

Acidities and homolytic bond dissociation energies of the αC—H bonds in ketones in DMSO

1990 ◽  
Vol 68 (10) ◽  
pp. 1714-1718 ◽  
Author(s):  
Frederick G. Bordwell ◽  
John A. Harrelson Jr
Keyword(s):  
Gas Phase ◽  
Radical Cations ◽  
Bond Dissociation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Oxidation Potentials ◽  
Stabilization Energies ◽  
Conjugate Bases

Equilibrium acidities in DMSO are reported for nine cycloalkanones, acetone, acetophenone, and 19 of their α-substituted derivatives. Oxidation potentials in DMSO for the conjugate bases of most of these ketones are also reported. Combination of these EOX(A−) and pKHA values gives estimates of the homolytic bond dissociation energies (BDEs) of the acidic C—H bonds in the ketones. The ΔBDEs, relative to the BDE of CH3-H, or a parent ketone, provide a measure of the radical stabilization energies (RSEs) of the corresponding radicals. The effects of successive α-Me and α-Ph substitutions on RSEs, relative to those of CH3COCH2-H or PhCOCH2-H, are similar to those reported in the gas phase for methane. The RSE for the MeĊHCOPh radical, relative to CH3• is 17 kcal/mol, which is smaller than the sum of the RSEs of the MeCH2• and PhCOCH2• radicals relative to CH3• (7 + 12 = 19), contrary to the prediction of the captodative postulate. When G in PhCOCH2G is PhCO, CH3CO, or CN the ΔBDEs (relative to PhCOCH2-H) are 0, 1, and 3 respectively; for MeCOCH2SO2Ph, PhCOCH2SO2Ph, and PhCOCH2NMe3+ the ΔBDEs are −5, −2, and −4, respectively. The BDEs in C5, C6, C7, C8, C10, and C12 cycloalkanones are within ±2.5 kcal/mol of that of 3-pentanone. Acetophenones bearing meta or para substituents all have BDEs of 93-94 kcal/mol. Ketone radical cations, [RCOR′]+•, appear to be superacids with estimated [Formula: see text] values below −25. Keywords: acidities, bond dissociation energies, ketones.

scholarly journals Experimental bond dissociation energies of benzylpyridinium thermometer ions determined by threshold-CID and RRKM modeling

2017 ◽  
Vol 417 ◽  
pp. 69-75 ◽  
Author(s):  
David Gatineau ◽  
Antony Memboeuf ◽  
Anne Milet ◽  
Richard B. Cole ◽  
Héloïse Dossmann ◽  
...  
Keyword(s):  
Bond Dissociation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Thermometer Ions
Sign in / Sign up

Export Citation Format

Share Document