Influence du substituant tertiobutyl-4 sur les constantes d'acidité du cation cyclohexylammonium et de l'acide cyclohexane carboxylique dans les milieux mixtes eau–DMSO et méthanol–DMSO

1976 ◽  
Vol 54 (12) ◽  
pp. 1899-1905 ◽  
Author(s):  
John T. Edward ◽  
Patrick G. Farrell ◽  
Jitka Kirchnerova ◽  
Jean-Claude Halle ◽  
Robert Schaal
Keyword(s):  
Dissociation Constants ◽  
Potentiometric Method ◽  
Acid Dissociation ◽  
Cyclohexane Ring ◽  
Acid Dissociation Constants ◽  
Tert Butyl ◽  
Butyl Group ◽  
Tert Butyl Group ◽  
Solvent Molecules

Acid dissociation constants for the compounds 1–6 in water–DMSO and methanol–DMSO of varying composition have been determined by a potentiometric method. In all solvents the equatorial group ionized more easily, by gain or loss of a proton, than the axial group, but in the more aqueous solvents the presence of a tert-butyl group across the cyclohexane ring inhibited this ionization slightly. An explanation based on displacement of solvent molecules from the outer solvation sphere is advanced.

Re-examination of the Kirkwood–Westheimer theory of electrostatic effects. III. Dissociation constants of cis-3- and trans-4-substituted cyclohexanecarboxylic acids in water–dimethyl sulfoxide mixtures

1978 ◽  
Vol 56 (8) ◽  
pp. 1130-1133 ◽  
Author(s):  
Jitka Kirchnerova ◽  
Patrick G. Farrell ◽  
John T. Edward ◽  
Jean-Claude Halle ◽  
Robert Schaal
Keyword(s):  
Dimethyl Sulfoxide ◽  
Dissociation Constant ◽  
Dissociation Constants ◽  
Solvent Composition ◽  
Potentiometric Method ◽  
Acid Dissociation ◽  
Electrostatic Effects ◽  
Acid Dissociation Constants ◽  
Cyclohexanecarboxylic Acid

Acid dissociation constants of two cis-3- and of four trans-4-substituted cyclohexanecarboxylic acids in water – dimethyl sulfoxide mixtures of varying composition were determined by a potentiometric method. Results have been analyzed according to the model of Kirkwood and Westheimer, and shown to differ from calculated values because of certain oversimplifications built into the model. Dissociation constant differences between cyclohexanecarboxylic acid and the compounds studied vary only slightly with changing solvent composition.

The dissociation constants of ethylene diammonium and hexamethylene diammonium ions from 0° to 60° C

1952 ◽  
Vol 215 (1122) ◽  
pp. 416-429 ◽  
Keyword(s):  
Heat Capacity ◽  
Free Energy ◽  
Liquid Water ◽  
Dissociation Constants ◽  
Heat Content ◽  
Acid Dissociation ◽  
Ionic Charge ◽  
Acid Dissociation Constants ◽  
Heat Capacity Changes ◽  
Solvent Molecules

The two acid dissociation constants of the ethylene diammonium ion and the hexamethylene diammonium ion in water have been determined, using an e.m.f. method, from 0 to 60° C. Measurements have been made at several ionic strengths to allow thermodynamic dissociation constants to be derived, and from these the free energy, heat content, entropy and heat capacity changes accompanying the dissociations have been computed. These quantities are discussed in relation to the size of the diamine molecule, and orientation of solvent molecules by the ionic charges. It is concluded that the range over which a single ionic charge causes a significant change in the structure of liquid water is about 5 Å.

Medium-sized cyclophanes, part 59:1 Nitration of [3.3]- and [3.3.3]metacyclophanes — Through-space electronic interactions between two or three benzene rings

2002 ◽  
Vol 80 (2) ◽  
pp. 207-215 ◽  
Author(s):  
Takehiko Yamato ◽  
Koji Tsuchihashi ◽  
Noriko Nakamura ◽  
Mai Hirahara ◽  
Hirohisa Tsuzuki
Keyword(s):  
Acetic Anhydride ◽  
Electronic Interaction ◽  
Reaction Conditions ◽  
Tert Butyl ◽  
Mixed Acid ◽  
Butyl Group ◽  
Tert Butyl Group ◽  
Starting Compound ◽  
Nitration Product ◽  
Fuming Nitric Acid

The two tert-butyl groups of anti-6,15-di-tert-butyl-9,18-dimethoxy[3.3]metacyclophane (anti-4) are both ipso-nitrated even under mild reaction conditions such as copper(II) nitrate in an acetic anhydride solution because of the decreased deactivation of the second aromatic ring by the introduced nitro group. On the other hand, anti-5,13-di-tert-butyl-8,16-dimethoxy[2.2]metacyclophane (anti-1) undergoes replacement of only one tert-butyl group under the same reaction conditions. The higher yields of the twofold ipso-nitration product anti-7 were obtained in nitration of anti-4 with fuming nitric acid or mixed acid (HNO3–H2SO4). Thus, the number of ipso-nitrations at the tert-butyl groups of anti-4 was strongly affected by the reactivity of the nitration reagent. Nitration of the corresponding syn-conformer syn-4 with copper(II) nitrate in an acetic anhydride solution, however, led only to the recovery of the starting compound. The presently developed procedure was further applied to the direct removal of the tert-butyl group by electrophilic substitution of the larger-sized ring macrocyclic metacyclophanes, cone- and partial-cone-tri-tert-butyl[3.3.3]metacyclophanes 11.Key words: [3n]metacyclophanes, conformation, ipso-nitration, through-space electronic interaction, crystal structure.

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