The strength of the O−O bond is fundamental importance in a variety chemical processes. Traditionally, value 34 kcal/mol has been ascribed to generic dissociation energy. present, high-level ab initio calculations indicate that average energy significantly higher, ca. 45 kcal/mol, and sensitive bonding environment. Calculations at G2 level theory give enthalpies 298 K 50 for HOOH, CH3OOH, 39 CH3OOCH3, 48 HC(O)OOH CH3C(O)OOH. G2(MP2) results are similar and, additionally, 38 diacetyl...

Ab initio calculations at the G2, G3, and CBS-Q levels of theory have been applied to question origin ring strain in a series unsaturated hydrocarbons. In addition angular germane all three-membered hydrocarbons, general trend is evidence that suggests increased (SE) small alkenes may be attributed part their relatively weak allylic C−H bonds. The high energy cyclopropene (54.1 kcal/ mol) largely strain. anomalously low SE cyclobutene relative cyclobutane (ΔSE = 4 kcal/mol) consequence...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectronic structure and reactivity of dioxirane carbonyl oxideRobert D. Bach, Jose L. Andres, Amy Owensby, H. Bernhard Schlegel, Joseph J. W. McDouallCite this: Am. Chem. Soc. 1992, 114, 18, 7207–7217Publication Date (Print):August 1, 1992Publication History Published online1 May 2002Published inissue 1 August 1992https://pubs.acs.org/doi/10.1021/ja00044a037https://doi.org/10.1021/ja00044a037research-articleACS PublicationsRequest reuse...

Both density functional theory (DFT) (B3LYP) and CCSD ab initio calculations were employed in a theoretical investigation of the mechanism thiolate−disulfide exchange reactions. The reaction pathway for degenerate reactions with dimethyl disulfide has been shown to proceed through SN2-like transition structure that is very close energy corresponding trisulfur anionic intermediate ([δ-S−S−Sδ-]). When relatively small substituents are involved, level must be increased make this rather subtle...

Iron-containing molecules and ions with various types of bonding were calculated using DFT theory (B3LYP functional) an energy-adjusted effective core potential for iron (ECP(S)). Examination geometries, bond dissociation energies, ionization enthalpies formation, harmonic frequencies their comparison experimental higher level (CCSD(T), MCPF, CASSCF) computational data show that B3LYP/ECP(S) calculations iron-containing species are capable giving reliable results. The energies interactions...

High level ab initio calculations have been applied to the estimation of ring strain energies (SE) a series three- and six-member compounds. The SE cyclohexane has estimated be 2.2 kcal/mol at CBS-APNO theory. cyclopropane increased 28.6 after correction for one-half cyclohexane. SEs carbonyl-containing three-member compounds CBS-Q by their combination with produce reference compound. cyclopropanone (5), simplest α-lactone (6) [oxiranone], α-lactam (7) [aziridinone] predicted 49, 47, 55...

Ring strain energies (SEs) and enthalpies of hydrogenation (ΔHhyd) a series E- Z-alkenes, cyclic alkynes allenes (C5−C9) are computed at the G3 level theory. The SE for cycloheptyne, cyclohexyne, cyclopentyne calculated to be 25.4, 40.1, 48.4 kcal/mol, respectively. E-cycloheptene E-cyclohexene 25.2 49.3 kcal/mol (G3). cyclooctyne is 2.0 greater than that E-cyclooctene (17.9 kcal/mol) but only 7.7 cyclooctane. 3,3-difluorocyclooctyne (DIFO) predicted slightly reduced (ΔSE = 2.6 relative...

When dealing with organic peroxides in both laboratory and industrial applications, the relative strengths of O-O bond are vital importance, from a safety mechanistic perspective. Although it is well known that such oxidizing agents highly reactive, reliable dissociation energies (BDEs) have only recently been established. In an earlier report, we suggested median BDE value ca. 45 kcal/mol for variety well-known based upon G2 ab initio calculations. present calculated twenty varying...

Bond dissociation energy (BDE) has been calculated for a series of compounds that contain N-O bonds. These structures encompass model N,N,O-trisubstituted hydroxylamines include O-methoxy, O-acyl, and O-phenyl hydroxylamines. The calculations used three accurate composite methods, CBS-QB3, CBS-APNO, G4 methods the computationally more affordable M06-2X/6-311+G(3df,2p) density functional theory (DFT) functional. single-bond BDEs are 5-15 kcal/mol higher than generic BDE 48 quoted in...

High-level ab initio molecular orbital calculations at the G2(+) level of theory have been carried out on identity front-side nucleophilic substitution reactions with retention configuration, X- + CH3X, for X = F, Cl, Br, and I. Overall gas-phase barrier heights do not show a strong variation halogen atom are calculated to be 184.5 (X F), 193.8 Cl), 178.9 Br), 171.4 kJ mol-1 I), substantially higher than corresponding barriers back-side attack (−8.0 11.5 5.8 6.5 I). The difference between...

The performance of the B3LYP density functional theory calculations has been studied for epoxidation reactions ethylene, propene, and cis- trans-2-butene with peroxyformic acid ethylene dioxirane dimethyldioxirane. transition structures propene dimethyldioxirane calculated at level as well QCISD CCSD levels are symmetrical nearly identical C−O bond distances, whereas MP2 favor unsymmetrical structures. geometrical parameters using close to those found levels. While activation barriers...

The B3LYP variant of DFT has been used to study the mechanism S−S bond scission in dimethyl disulfide by a phosphorus nucleophile, trimethylphospine (TMP). reaction is highly endothermic gas phase and requires significant external stabilization charged products. calculations (B3LYP) were performed with explicit (water molecules added) implicit solvent corrections (COSMO model). transition structures for this SN2 displacement number model systems have located fully characterized. barriers...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular orbital approach to the mechanism of electrophilic additions olefinsRobert D. Bach and H. Fred HenneikeCite this: J. Am. Chem. Soc. 1970, 92, 19, 5589–5602Publication Date (Print):September 1, 1970Publication History Published online1 May 2002Published inissue 1 September 1970https://pubs.acs.org/doi/10.1021/ja00722a010https://doi.org/10.1021/ja00722a010research-articleACS PublicationsRequest reuse permissionsArticle...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhosphonium Salts. II. 2-Bromophenetole and Triphenylphosphorus as Novel Phosphonioethylation PrecursorsEdward E. Schweizer Robert D. BachCite this: J. Org. Chem. 1964, 29, 7, 1746–1751Publication Date (Print):July 1, 1964Publication History Published online1 May 2002Published inissue 1 July 1964https://pubs.acs.org/doi/10.1021/jo01030a020https://doi.org/10.1021/jo01030a020research-articleACS PublicationsRequest reuse permissionsArticle...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA theoretical model for the orientation of carbene insertion into saturated hydrocarbons and origin activation barrierRobert D. Bach, Ming Der Su, Ehab Aldabbagh, Jose L. Andres, H. Bernhard SchlegelCite this: J. Am. Chem. Soc. 1993, 115, 22, 10237–10246Publication Date (Print):November 1, 1993Publication History Published online1 May 2002Published inissue 1 November...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOxidation of Amines and Sulfides with Hydrogen Peroxide Alkyl Peroxide. The Nature the Oxygen-Transfer StepRobert D. Bach, Ming-Der Su, H. Bernhard SchlegelCite this: J. Am. Chem. Soc. 1994, 116, 12, 5379–5391Publication Date (Print):June 1, 1994Publication History Published online1 May 2002Published inissue 1 June 1994https://pubs.acs.org/doi/10.1021/ja00091a049https://doi.org/10.1021/ja00091a049research-articleACS PublicationsRequest reuse...

A series of model theoretical calculations are described that suggest a new mechanism for the oxidation step in enzymatic cytochrome P450 hydroxylation saturated hydrocarbons. class metastable metal hydroperoxides is involves rearrangement ground-state hydroperoxide to its inverted isomeric form with hydroxyl radical hydrogen bonded oxide (MO-OH --> MO....HO). The activation energy this somersault motion FeO-OH group 20.3 kcal/mol porphyrin iron(III) [Por(SH)Fe(III)-OOH(-)] produce ferryl...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectronic factors influencing the activation barrier of Diels-Alder reaction. An ab initio studyRobert D. Bach, Joseph J. W. McDouall, H. Bernhard Schlegel, and Gregory WolberCite this: Org. Chem. 1989, 54, 12, 2931–2935Publication Date (Print):June 1, 1989Publication History Published online1 May 2002Published inissue 1 June 1989https://pubs.acs.org/doi/10.1021/jo00273a029https://doi.org/10.1021/jo00273a029research-articleACS PublicationsRequest...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEpoxidation of alkenes with trichloroacetonitrile/hydrogen peroxide in a neutral biphasic solvent systemLuis A. Arias, Stevie Adkins, Christopher J. Nagel, and Robert D. BachCite this: Org. Chem. 1983, 48, 6, 888–890Publication Date (Print):March 1, 1983Publication History Published online1 May 2002Published inissue 1 March 1983https://doi.org/10.1021/jo00154a031RIGHTS & PERMISSIONSArticle Views905Altmetric-Citations56LEARN ABOUT THESE...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDimerization of racemic and optically active 1,2-cyclononadieneWilliam Robert Moore, D. Bach, Thomas M. OzretichCite this: J. Am. Chem. Soc. 1969, 91, 21, 5918–5919Publication Date (Print):October 1, 1969Publication History Published online1 May 2002Published inissue 1 October 1969https://pubs.acs.org/doi/10.1021/ja01049a059https://doi.org/10.1021/ja01049a059research-articleACS PublicationsRequest reuse permissionsArticle...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular asymmetry. IX. Partial resolution and asymmetric synthesis of 1,2-cyclononadieneArthur C. Cope, William Robert Moore, D. Bach, Hans J. S. WinklerCite this: Am. Chem. Soc. 1970, 92, 5, 1243–1247Publication Date (Print):March 1, 1970Publication History Published online1 May 2002Published inissue 1 March 1970https://pubs.acs.org/doi/10.1021/ja00708a023https://doi.org/10.1021/ja00708a023research-articleACS PublicationsRequest reuse...

The C6H5X + X- (X = Cl−I) gas phase SNAr reactions proceed via a single-step mechanism without the formation of stable C6H5X2- σ-complex. C2v structures Cl−I), which are transition in these reactions, predicted to be considerably higher energy (by 102.3 (Cl), 100.3 (Br), and 103.7 (I) kJ mol-1 at MP2/6-31+G(d) ZPE(HF/6-31+G(d)) level) than their isolated reactants. These high overall barriers suggest that it would hardly possible observe monosubstituted halobenzenes with halide anions phase....

A 6.8 fold increase in the rate of epoxidation (Z)-cyclooctene with m-chloroperbenzoic acid is observed upon addition catalyst trifluoroacetic acid. Kinetic and theoretical studies suggest that this due to complexation peroxy undissociated (HA) rather then protonation The transition structure for oxidation ethylene protonated peroxyformic exhibits a spiro orientation electrophilic oxygen at QCISD/6-31G(d) level complexed (HCO3H·HA) state also essentially ab initio density functional levels....

A theoretical study specifically addresses the question of whether nucleophilic addition to carbonyl groups acid chlorides, esters, and anhydrides involves an addition−elimination pathway or proceeds by a concerted SN2-like mechanism in absence generally assumed tetrahedral intermediate. Density functional calculations [B3LYP/6-31+G(d,p)] establish that chloride ion exchange reactions with both formyl acetyl proceed π attack on CO bond. No discernible intermediate typical was found either...