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  • Organic Chemistry  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 4 (1991), S. 13-18 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The alkaline hydrolysis of nine para-substituted phenyl esters of para-substituted benzoates was studied in the presence and absence of hexadecyltrimethylammonium bromide (CTAB) micelles. The second-order rate constant for alkaline hydrolysis in CTAB micelles (K2m) was calculated using a pseudo-phase ion-exchange model. the substituent effect on the second-order rate constant in the aqueous phase (k2w) and on k2m was analysed using Hammett's σ ρ plots. The calculated ρ values in micelles were 0.8 unit. larger than those in water. The effective low dielectric constant in the micellar surface may be responsible for the general effect of increasing the sensitivity of reactions to the electronic effect of substituents in micelles.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 4 (1991), S. 19-24 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rate of intramolecular degradation of cephaclor, involving the attack of the amino group at C-17 (N-18) on the β-lactam carbonyl, was increased up to 50-fold by neutral (polyoxyethylene-23 lauryl ether; Brij) and zwitterionic [3-(N-dodecyl-N, N-dimethylammonium) propane 1-sulphonate; (SDP)] micelles. The rate of OH- attack on cephaclor was increased 2-3-fold by Brij and SDP micelles. In the absence of micelles the rate of intramolecular degradation of cephaclor increased by up to 2-fold by addition of organic solvents. Distance calculations, based on the crystal structure of the antibiotic, showed that the intramolecular degration can only proceed in a conformation involving a cis-amide bond (N-14 - C-15). Micellar catalysis of the intramolecular degradation process was proposed to be due to the stabilization of the reactive conformation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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