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  • Organic Chemistry  (5)
  • Bipolar lipid  (3)
  • Theoretical, Physical and Computational Chemistry  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Thermotropic properties of bipolar lipids of Sulfolobus solfataricus and of their mixtures with dipalmitoylphosphatidylcholine
    Amsterdam : Elsevier
    Biophysical Chemistry 22 (1985), S. 27-35 
    Details
    ISSN: 0301-4622
    Keywords: Bipolar lipid ; DSC ; Hydration ; Interaction ; Orientation
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0301-4622(85)80023-5
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  • 2
    Electronic Resource
    Electronic Resource
    Vesicles from mixtures of bipolar archaebacterial lipids with egg phosphatidylcholine
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 732 (1983), S. 714-718 
    Details
    ISSN: 0005-2736
    Keywords: (Caldariella acidophila) ; Archaebacterial lipid ; Asymmetric distribution ; Bipolar lipid ; Liposome ; Phosphatidylcholine
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2736(83)90252-3
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  • 3
    Electronic Resource
    Electronic Resource
    Phase transitions of bipolar lipids of thermophilic archaebacteria
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 861 (1986), S. 420-428 
    Details
    ISSN: 0005-2736
    Keywords: (S. solfataricus) ; Archaebacterium ; Bipolar lipid ; Differential scanning calorimetry ; Lipid polymorphism ; Phase transition
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2736(86)90450-5
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  • 4
    Electronic Resource
    Electronic Resource
    Several mechanisms in the elimination kinetics of ω-chlorocarboxylic acids in the gas phase (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 133-138 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the gas-phase pyrolysis of ω-chlorocarboxylic acids were examined in a seasoned static reaction vessel and in the presence of at least twice the amount of the free radical inhibitor cyclohexene or toluene. In conformity with the available experimental data on rate determination, these reactions proved to be unimolecular and obeyed a first-order rate law. The presence of the primary chlorine leaving group in Cl(CH2)nCOOH (n = 1-4) showed a change in mechanism from intramolecular displacement of the Cl leaving group by the acidic hydrogen of the COOH to anchimeric assistance of the carbonyl COOH to the C—Cl bond polarization in the transition state. This mechanistic consideration is nearly the same for the series of 2-, 3-, and 4-chlorobutyric acids. The chlorine atom at the 2-position of acetic, propionic and butyric acids is dehydrochlorinated through a prevailing reaction path involving a polar five-membered cyclic transition state.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080302
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  • 5
    Electronic Resource
    Electronic Resource
    Rearrangement in the homogeneous elimination kinetics of 3-chloro-2,2-dimethylpropan-1-ol in the gas phase (1996)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 9 (1996), S. 583-587 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 3-Chloro-2,2-dimethylpropan-1-ol was pyrolysed in a static system at 410·0-459·1 °C and 62-179 Torr. The reaction, in a seasoned vessel and in the presence of the free radical suppressor propene, is homogeneous, unimolecular, and follows a first-order rate law. The rate coefficient follows the Arrhenius equation: log k1 (s-1) = (13·14±0·15) - (218·8 ± 2.1) kJ mol-1 (2·303RT)-1. The products are isobutene, formaldehyde and HCl gas. The exclusive intramolecular migration of the CH2OH group to the positively charged carbon atom, from the C(SINGLE BOND)Cl bond polarisation, appears to proceed by way of an intimate ion-pair type of mechanism. The intermediate 3-methylbut-3-en-1-ol, under the reaction conditions, undergoes a six-centered decomposition characteristic of β-hydroxyalkenes to produce isobutene, formaldehyde and HCl. The pyrolysis of the deuterated substrate, 3-chloro-2,2-dimethylpropan-1-[2H]ol, serves to support the mechanistic consideration assumed above.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Homogeneous, unimolecular, gas-phase elimination of leaving groups at the alkoyl side of carboxylic acids (1996)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 9 (1996), S. 348-354 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular gas-phase elimination kinetics of the series (Cl(CH2)nCOOH (n = 1-4), show changes in mechanisms from polar five-centered intramolecular displacement of the Cl leaving group by the acidic hydrogen of the COOH to neighboring group participation of the oxygen carbonyl of the COOH group. The mechanisms for the series 2-, 3- and 4-chlorobutyric acids are explained similarly as above. The leaving chloride at the 2-position of acetic, propionic, and butyric acids is displaced by the hydrogen of the COOH group through a prevaling path of a five- centered cyclic transition-state mechanism. This type of mechanism is also described for the pyrolysis of 2-hydroxy-, 2-alkoxy-, 2-phenoxy-, and 2-acetoxycarboxylic acids. The ease with which the groups at the 2-position of acetic and propionic acids are displaced by the H of COOH give rise the sequences AcO 〉 OH 〉 PhO 〉 EtO 〉 MeO 〉 Cl and AcO 〉 PhO 〉 Br 〉 EtO 〉 MeO 〉 MeO 〉 OH 〉 Cl, respectively. These two sequences differ only in the OH leaving group position. Additional work on glycolic acid pyrolysis is needed to explain the above differences.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular rearrangements in homogeneous gas-phase elimination reactions. Pyrolysis kinetics of alkyl methanesulphonates (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 85-94 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rates of elimination of several alkyl methanesulphonates were determined in a seasoned, static reaction vessel over the temperature range 300-420°C and the pressure range 28-163 Torr. The reactions are homogeneous, unimolecular and follow a first-order rate law. The overall rate coefficients are given by the following equations: for isobutyl methanesulphonate, log k1 (s-1) = (12·51 ± 0·38) - (177·0 ± 2·1) kJ mol-1 (2·303RT)-1; for 2-phenyl-1-propyl methanesulphonate, log k1(s-1) = (12·62 ± 0·04) - (176·2 ± 0·5) kJ mol-1 (2·303RT)-1; for neopentyl methane-sulphonate, log k1(s-1) = (13·35 ± 0·42) - (198·2 ± 5·2) kJ mol-1 (2·303RT)-1; and for 3-chloro-2,2-dimethyl-1-propyl methanesulphonate, log k1(s-1) = (13·87 ± 0·42) - (218·2 ± 5·4) kJ mol-1 (2·303RT)-1. Rearrangements in these methanesulphonate pyrolyses may proceed via an intimate ion-pair type of mechanism. Consequently, the results appear to confirm that intramolecular migration through autosolvation is possible in gas-phase elimination reactions of certain types of organic molecules.
    Additional Material: 11 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060204
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  • 8
    Electronic Resource
    Electronic Resource
    Elimination kinetics and mechanisms for several 2-alkoxyacetic acids in the gas phase (1996)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 9 (1996), S. 787-794 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the gas-phase elimination of three 2-alkoxyacetic acids were investigated in a static system, seasoned with allyl bromide, and in the presence of the free chain radical inhibitor cyclohexene. The working temperature and pressure range were 350·4-410·8°C and 57-261·5 torr, respectively. The reactions proved to be homogeneous and unimolecular and to follow a first-order rate law. The temperature dependence of the rate coefficients is given by the following equations: for 2-methoxyacetic acid, log k1 (s-1) = (12·10 ± 0·22)-(193·3 ± 2·8) kJ mol-1 (2·303RT)-1; for 2-ethoxyacetic acid, log k1 (s-1) = (12·76 ± 0·29)-(199·6 ± 3·7) kJ mol-1 (2·303RT)-1; and for 2-isopropoxyacetic acid, log k1 (s-1) = (12·40 ± 0·32)-(193·7 ± 3·9) kJ mol-1 (2·303RT)-1. The alkyl group R in ROCH2COOH does not seem to exert a significant effect on the rates. It is postulated that the predominant mechanism for the decomposition of the alkoxy acids involves a five-membered cyclic transition state, where the elimination of the RO substituents is assisted by the acidic proton of the COOH group. © 1996 John Wiley & Sons, Ltd.
    Additional Material: 8 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Elimination kinetics and mechanism of primary, secondary and tertiary α-hydroxycarboxylic acids in the gas phase (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 54-58 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rates of elimination of primary, secondary and tertiary α-hydroxycarboxylic acids were determined in a seasoned, static reaction vessel over the temperature range 280-390°C and the pressure range 30-201 Torr. The reactions, in the presence of a free radical inhibitor, are homogeneous, unimolecular and follow a first-order rate law. The rate coefficients are given by the following equations: for glycolic acid, log k1 (s-1) = (14·03 ± 0·24) - (209·3 ± 1·5) kJ mol-1 (2·303RT)-1; for lactic acid, log k1 (s-1) = (12·24 ± 0·11) - (182·8 ± 1·3) kJ mol-1 (2·303RT)-1; and for 2-hydroxyisobutyric acid, log k1 (s-1) = (12·91 ± 0·13) - (174·7 ± 1·5) kJ mol-1 (2·303RT)-1. The basicity and the ease with which the hydroxy group is removed from primary to tertiary α-hydroxycarboxylic acids are reflected in rate enhancement. The mechanism of these eliminations appears to proceed through a semi-polar five-membered cyclic transition state.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060109
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  • 10
    Electronic Resource
    Electronic Resource
    Acidity constants of benzamide and some Ortho-substituted derivatives (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 101-106 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acidity constants of benzamide and seven ortho-substituted derivatives were determined. Except for o-nitrobenzamide, all the amides exhibit medium effects. The data were treated by vector analysis. o-Aminobenzamide displays two protonation equilibria. The second acidity constant was determined by vector analysis and by the excess acidity function, since the acid strength provided by perchloric acid is insufficient for complete protonation. Different acidity functions and the ortho substituent effect on ionization of the amide group are compared.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060206
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