Revised group additivity parameters for the enthalpies of formation of oxygen-containing organic compounds

Eigenmann, H. K.; Golden, D. M.; Benson, Sidney W.

doi:10.1021/j100632a019

Cited by 117 publications

(94 citation statements)

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“…In oxetane itself, the strain energy has been determined to be 106 kJ mol À1 , only 6 kJ mol À1 less than in oxirane and 81 kJ mol À1 more than in tetrahydrofuran. [52] Oxetane undergoes hydrolysis catalyzed by sulfuric or perchloric acid in aqueous dioxane almost as rapidly as does ethylene oxide. In the presence of base, however, ring opening of oxetane is very slow: oxirane undergoes hydrolysis three orders of magnitude faster than oxetane under alkaline conditions.…”

Section: Ring-opening Reactions Of Oxetanesmentioning

confidence: 99%

Oxetanes as Versatile Elements in Drug Discovery and Synthesis

et al. 2010

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Sizable resources, both financial and human, are invested each year in the development of new pharmaceutical agents. However, despite improved techniques, the new compounds often encounter difficulties in satisfying and overcoming the numerous physicochemical and many pharmacological constraints and hurdles. Oxetanes have been shown to improve key properties when grafted onto molecular scaffolds. Of particular interest are oxetanes that are substituted only in the 3-position, since such units remain achiral and their introduction into a molecular scaffold does not create a new stereocenter. This Minireview gives an overview of the recent advances made in the preparation and use of 3-substituted oxetanes. It also includes a discussion of the site-dependent modifications of various physicochemical and biochemical properties that result from the incorporation of the oxetane unit in molecular architectures.

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Section: Ring-opening Reactions Of Oxetanesmentioning

confidence: 99%

Oxetanes as Versatile Elements in Drug Discovery and Synthesis

et al. 2010

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“…The relative energies of the states or intermediates marked by a horizontal bar have been drawn from experimental data wherever possible, or else were taken from the semiempirical calculations described above. The reaction Z-E (1)+1 is estimated to be 39 kcaVmo1 exothermic using Benson's tables of group increments [20]. This value may be about five kcaVmol too high considering the most recent thermochemical estimate for acetone @ 2-propenol [21], and allowing for a small amount of resonance energy in Z-E (1) [22].…”

mentioning

confidence: 98%

The Photoenolization of 2‐Methylacetophenone and Related Compounds

Haag¹,

Wirz²,

Wagner³

1977

Helvetica Chimica Acta

194

141

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SummaryA reinvestigation of 2-methylacetophenone (1) by ns flash photolysis has provided detailed evidence for the reaction sequence of photoenolization. The triplet reaction proceeds adiabatically from the lowest excited triplet state of the ketone, 3K (l), to the enol excited triplet state, 3E (l), which decays both to enol and ketone ground state. The Z-and E-isomers of the photoenol, Z-E (1) and E-E (1) are formed in about equal yield by the triplet pathway, while direct enolization from the lowest excited singlet state of 1 yields (predominantly) the 2-isomer. Intramolecular reketonization from 2-E (1) to 1 proceeds at a rate of ca. loss-' in cyclohexane, but can be retarded to ca. 104s-' in hydrogen-bond-acceptor solvents. The proposed mechanism is summarized in Scheme 1 and rationalized on the basis of a state correlation diagram, Scheme 2. 3,3,6,8-Tetramethyl-l-tetralone (2) was used as a reference compound with fixed conformational position of the carbonyl group, and some results from a brief investigation of 2,4-dimethylbenzophenone (3) are also reported.We have recently found [ 11 that the photoenolization of 5-methyl-l,6naphtho-quinone takes place with high efficiency and that the thermal reketonization to starting material is very fast at room temperature. The great retardation of the back reaction from a rate of ca. 105s-' in cyclohexane to ca. lo's-' in hexamethyl phosphoric acid triamide (HMPA) was striking but not surprising: The solvation of the enolic proton in hydrogen-bond-acceptor (HBA) solvents obviously provides an I)

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“…It is defined as an energy excess between the cyclic molecule and an appropriately chosen strain‐free counterpart 15. Therefore, it is obtained as a difference between the Δ H f for the ring compound and the hypothetical strain‐free Δ H f calculated for the same molecule by summing up the respective fragments 16. The ring‐strain energy thus turns out to be a magnitude proportional to the barrier height for a strain‐free acyclic molecule to form a cyclic ring.…”

Section: Resultsmentioning

confidence: 99%

Theoretical studies of isomerization barriers of 2‐pentoxy radical and its products

Lin

2002

Int J of Quantum Chemistry

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This article deals with the calculation of isomerization reaction of 2-pentoxy radical via its possible processes to form the stable products by density functional theory. We studied the intramolecular hydrogen transfers from the five carbon positions to the oxygen atom of 2-pentoxy and then followed by successive transfers from the unstable hydroxy radical to the final stable one. There are five paths of hydrogen transfer discussed, which include the transition structures of pseudo three-, four-, five-, and six-membered rings. The results indicated that the rate constant of the process via six-membered ring transition state calculated at the B3LYP/6-311ϩϩG** level was close to the experimental value and it had the lowest calculated energy barrier among all, 8.63 kcal/mol. We also studied the isomerization barriers of the firststage product to form the most stable conformation via possible paths. The calculated lowest barrier was 18.41 kcal/mol via a five-membered ring process.

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Revised group additivity parameters for the enthalpies of formation of oxygen-containing organic compounds

Cited by 117 publications

References 1 publication

Oxetanes as Versatile Elements in Drug Discovery and Synthesis

Oxetanes as Versatile Elements in Drug Discovery and Synthesis

The Photoenolization of 2‐Methylacetophenone and Related Compounds

Theoretical studies of isomerization barriers of 2‐pentoxy radical and its products

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