Effect of small changes in orientation on reaction rate

Storm, Dan R.; Koshland, Daniel E.

doi:10.1021/ja00771a046

Cited by 79 publications

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“…In fact the difference between a theoretical curve based on eq. [12] using the constants of Table 2 and the simple empirical rate law of eq. [4] is not outside experimental error.…”

Section: Discussionmentioning

confidence: 99%

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The tetrahedral intermediate of a lactonization reaction

McClelland¹,

Alibhai²

1981

Can. J. Chem.

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ROBERTA. M C C L E L L A N D~~~MASUMA ALIBHAI. Can. J. Chem. 59, 1169Chem. 59, (1981. 'The hydrolysis of the ortho ester 1,l-diethoxy-l,3-dihydroisobenzofuran (1) is described. This hydrolysis proceeds with initial expulsion of an exocyclic ethoxy group, producing upon hydration of the oxocarbonium ion I-hydroxy-1-ethoxy-1,3-dihydroisobenzofuran (7), the tetrahedral intermediate of the lactonization of ethyl (2-hydroxymethyl)benzoate (6) to phthalide (8). Based on the kinetic behavior of the ortho ester hydrolysis, the pH variation in the ratio of 6:8 initially formed from the ortho ester, and the kinetic behavior of the lactonization reaction, rate constants for the breakdown of the tetrahedral intermediate 7 have been determined, along with the equilibrium constant for its formation from the hydroxy ester 6. The breakdown occurs in an extremely rapid hydroxide-ion-catalyzed reaction, with the rate being at the diffusion limit. Hydronium ion catalysis is also observed; this breakdown is also rapid although considerably less so than the hydroxide ion reaction. The changeover from H+ to OH-catalysis occurs at pH 3.5. The rate of breakdown is a minimum at this point, and corresponds to a half-life for the tetrahedral intermediate of about 0.1 s. It is concluded that this allows sufficient time for conformational changes in the tetrahedral intermediate prior to breakdown; this factor must be taken into account in stereoelectronic considerations.ROBERT A. MCCLELLAND et MASUMA ALIBHAI. Can. J. Chem. 59,1169Chem. 59, (1981. On dkcrit I'hydrolyse de I'ortho ester diethoxy-1,l dihydro-1,3 isobenzofuranne (1). Cette hydrolyse se fait avec une expulsion initiale d'un groupe ethoxy exocyclique conduisant aprks hydratation a I'ion oxocarbonium hydroxy-1 Cthoxy-1 dihydro-1,3 isobenzofuranne (7), I'intermediaire tttraedrique de la lactonisation du (hydroxymethy1)-2 benzoate d'ethyle (6) en phtalide (8). On a determine la constante de vitesse de rupture de I'intermediaire tttraedrique 7 ainsi que la constante d'equilibre conduisant a sa formation a partir de I'hydroxy ester 6 en se basant sur le comportement cinktique de I'hydrolyse de I'ortho ester, sur la variation du pH dans le rapport du produits 6:8 qui se forment initialement a partir de I'ortho ester et sur le comportement cinetique de la reaction de lactonisation. La rupture se produit au cours d'une reaction extrcmement rapide catalysee par I'ion hydroxyde dont la vitesse est limitee par la diffusion. On observe egalement la catalyse par I'ion hydronium; cette rupture est egalement rapide quoique considerablement plus faible que celle de la reaction catalysee par I'ion hydroxyde. Le changement de catalyseur de H+ a OH-se produit a un pH de 3,s. La vitesse de rupture est minimale i c e point et correspond a une demie-vie de I'intermediaire tetraedrique d'environ 0,l s. On en conclut que ceci accorde suffisamment de temps a des changements conformationnels de I'intermediaire tktrakdrique avant sa rupture. On doit tenir compte de ce facteur dans les considerations ste...

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“…In fact the difference between a theoretical curve based on eq. [12] using the constants of Table 2 and the simple empirical rate law of eq. [4] is not outside experimental error.…”

Section: Discussionmentioning

confidence: 99%

“…Aldroisobenzofuran (I), an ortho ester derived from though lactonization reactions have seen considerthe lactone phthalide. The hydrolysis of cyclic able investigation in a number of cases (12)(13)(14)(15)(16), dialkoxy ortho esters related to 1 (for example, 2) including the above hydroxy ester (15), no direct …”

Section: Ormentioning

confidence: 99%

The tetrahedral intermediate of a lactonization reaction

McClelland¹,

Alibhai²

1981

Can. J. Chem.

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“…A unique abiotic feature of these lactones, coincident with Baldwin's ring-closure rule (21), is that they exist in equilibria with relatively hydrophilic b-, g-, and d-hydroxy acids, respectively, when in aqueous systems. Specifically, the g-lactone moiety of ES/AS was converted into a g-hydroxy acid (HA) and corresponding carboxylate under the conditions: [ (22,23). Acid-catalyzed lactonization (/k LAC ) of g-hydroxy acids to form cis-fused g-lactones can occur rapidly and often the g-lactone (i.e.…”

Section: Inter-conversion Of Acid and Lactone Epianastrephin/ Anastrementioning

confidence: 99%

“…Acid-catalyzed lactonization (/k LAC ) of g-hydroxy acids to form cis-fused g-lactones can occur rapidly and often the g-lactone (i.e. closed ring) form is largely favored at equilibrium (23). However, these are not characteristic features of analogous transfused systems (24); ES/AS concentrations over 30 days at pH 5.5 comprised only Â1% of solutions fortified with ES/AS HA over the range 20Á408C.…”

Section: Inter-conversion Of Acid and Lactone Epianastrephin/ Anastrementioning

confidence: 99%

Environmentally regulated abiotic release of volatile pheromones from the sugar-based oral secretions of caribflies

Walse

Alborn

Teal

2008

Green Chemistry Letters and Reviews

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We report an abiotic mechanism for the emission of volatile insect pheromones that is controlled by environmentally induced change in the physicochemical properties of the sugar-based release matrix. Male Anastrepha suspensa (Loew) (caribflies) mark mating sites on leaf surfaces by depositing oral secretions that contain sugar, as well as, g-hydroxy acid and g-lactone forms of the diastereomeric aggregation pheromones, epianastrephin and anastrephin. The g-hydroxy acids extend emission over many days via aqueous equilibrium with the thermodynamically less preferred, but more volatile, g-lactones (Â100:1). A kinetic model, which supports a g-lactone diffusion-limited rate, was generated and tested by measuring the effect of temperature and humidity under fixed and ambient atmospheric inputs, respectively. Results show that pheromone release from the markings occurs with a periodicity that parallels relative humidity and complements the daily pattern of the caribflies' reproductive and aggregative activity. This study provides an example of a physicochemical-based inter-organism communication strategy that has been mechanistically linked to the abiotic environmental processing of volatile chemical signals. The exploitation of this natural connectivity will spur environmentally sustainable chemistries, particularly pheromone-based alternatives to insecticide application.

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“…Although quantitative electron density studies require data of greater accuracy than in the present study, residuals due to the aspherical bonding density are apparent in Fig. 2. enzymes, Koshland and co-workers have measured intramolecular reaction rates for norbornane molecules substituted with a variety of functional groups (Storm & Koshland, 1972). The title compound, a hydroxylactam, was synthesized by Hackney (1975) to serve, in its base-catalyzed rearrangement to an aminolactone, as a model for the rate-determining step in the hydrolysis of amides by chymotrypsin.…”

mentioning

confidence: 99%

6-endo-Hydroxy-3-endo-aminomethylbicyclo[2.2.1]heptane-2-endo-carboxylic acid lactam

Olson¹,

Templeton²,

Templeton³

1977

Acta Crystallogr Sect B

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2266 DICYANOTRISULFANE 0.0047(17) A respectively into the triple CN bond, when compared with the high-order refinement. This effect is generally observed in refinements of X-ray data (Coppens, 1974: Bats, 1976, and results from the aspherical distribution of the bonding electrons. As the structure is refined with a spherical atom model, the reported standard deviations in the atomic parameters do not contain these asphericity effects and are consequently underestimated. Fig. 2 shows a difference Fourier synthesis in the plane containing the SSCN group, based on the loworder reflections and the high-order atomic parameters. The data cut-off in this difference Fourier synthesis has deliberately been taken low, in order to reduce the noise level. Although quantitative electron density studies require data of greater accuracy than in the present study, residuals due to the aspherical bonding density are apparent in Fig. 2

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Effect of small changes in orientation on reaction rate

Cited by 79 publications

References 0 publications

The tetrahedral intermediate of a lactonization reaction

The tetrahedral intermediate of a lactonization reaction

Environmentally regulated abiotic release of volatile pheromones from the sugar-based oral secretions of caribflies

6-endo-Hydroxy-3-endo-aminomethylbicyclo[2.2.1]heptane-2-endo-carboxylic acid lactam

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