摘要:

The complexation constantsKof β-cyclodextrine with 13 ammonium surfactants were determined by a potentiometric method using electrodes selective to amphiphilic ions. Especially for C12, C14, and C16 tails, a model that provides for the formation of a second complex (β-CD)2M+, with aK1/K2ratio of about 600, provides a good fit with the experimental curves. Results show a poor influence of the polar group, for example in the case of the dodecyl chain. On the other hand, the pK1values and the hydrophobic tail length are linked by a linear relation up ton = 12 carbon atoms; beyond, pK1tends to be proportionally smaller and pK2more important.Keywords: surfactant, β-cyclodextrin, selective electrodes, complexation constants, potentiometric study.

ISSN:0008-4042    

DOI:10.1139/v91-270

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Reaction of eithern-Bu3SnCu(CN)Li (8) or (n-Bu3Sn)2Cu(CN)Li2(9) with 1,2-undecadiene gave 71–92% of a (Z/E) mixture of 1-tri-n-butylstannyl-2-undecene (27) accompanied by 8–32% of a mixture of (E)-2-tri-n-butylstannyl-2-undecene (28) and 2-tri-n-butylstannyl-1-undecene (29). When the above reactions were warmed to 0 °C,28and29were the major products. The mixed cuprates,10–14, gave the mixtures rich in vinylstannanes,28and29, along with27. Addition of Sn—Al reagents,15and16, or Sn—B reagents,18and19, to 1,2-undecadiene in the presence of 5 mol% of CuCN or CoCl2•(PPh3)2provided mixtures rich in vinylstannanes,28and29. However, with 1 equiv. of CuCN, mixtures rich in allylstannanes27were obtained. Reaction of 5-hydroxy-1,2-pentadiene with the Sn—Al reagents,15and16, gave 53–61% of a single 5-hydroxy-2-tri-n-butylstannyl-1-pentene (32) in the presence of 5 mol% of CoCl2•(PPh3)2. The stannylcopper adducts generated in the reaction of 1,2-undecadiene and8or9were treated with iodomethane to give 55–78% of a (Z/E: 67/33) mixture of 1-tri-n-butylstannyl-2-methyl-2-undecene (33). Addition of mixed silylcuprates,21,22, and23, to 1,2-undecadiene gave mixtures rich in (E)-2-dimethylphenylsilyl-2-undecene (35) and 2-dimethylphenylsilyl-1-undecene (36). A rationale for the putative adducts' formation is also presented.Keywords: Sn—Cu, Sn—Al, Sn—B reagents; putative adducts.

ISSN:0008-4042    

DOI:10.1139/v91-271

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The adsorption of several aromatic nitro compounds and the ion-exchange of heavy metal ions on electro-oxidized carbon fibres have been investigated using cyclic voltammetric and polarographic techniques. Electro-oxidation is performed by potentiostatic double pulse application. This procedure results in the generation of many functional —OH and —COOH groups with adsorptive and ion-exchanging properties.Multimolecular layers of adsorbed substances may be formed through a procedure of successive adsorption of the nitro-compound and electro-reduction to the corresponding amine, resulting in the attachment of considerable amounts of the nitro-compound to the carbon fibres.The ion-exchange capacity is estimated to be ca. 1 mequiv. g−1and with slight deviations it follows the rank Ag, Cu, Cd, Pb, Hg. After the electro-reduction of the exchanged metal ions, the ion-exchange process can be repeated several times. This procedure is of importance for the removal of significant amounts of heavy and toxic metals from industrial waste waters.Keywords: electro-oxidized carbon fibres, adsorption of aromatic nitro compounds, cation-exchange of heavy metals.

ISSN:0008-4042    

DOI:10.1139/v91-272

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The redox potential (ΔE1/2), electron affinity (EA), ionization potential (IP), coulomb repulsion integral (J12), and electronic transition energy (ECT) of several oxazolone derivatives in DMF were computed. A linear correlation was shown to exist between ΔE1/2andECT•The polarographic reduction was investigated in ethanolic-Theil buffer solutions. At pH ≤ 7.2, two waves were obtained representing the uptake of 2- and 4-electron steps respectively. In alkaline media, a third wave appeared seemingly a result of the hydrolysis of oxazolones. The rate of hydrolysis was determined and the electrode mechanism was elucidated and confirmed via spectrophotometric and coulometric analysis.Keywords: oxazolones, polarography, electrochemistry, electrode reaction, spectrophotometry, redox potential.

ISSN:0008-4042    

DOI:10.1139/v91-273

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

For polyfunctional compounds, free energies of transfer from gas to aqueous solution require corrections for the interactions of polar groups (Distant Polar Interactions). These corrections can be made with very few adjustable parameters by using a model of the solvation process assuming hydrogen bonding is the major source of the effect on free energy of transfer for polar groups, and that hydrogen bonding is perturbed by polar effects, measured by Taft σ*. Parameters evaluated for polyfluoro, polychloro, and polybromo compounds successfully predicted the free energies of transfer for mixed polyhalogen compounds. Preliminary parameters have been evaluated for ethers, amines, phenyl groups, nitriles, and esters.Keywords: free energy of transfer, distant polar interaction, hydrogen bonding, solvation.

ISSN:0008-4042    

DOI:10.1139/v91-274

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Chlorination of propiophenone in aqueous alkali at room temperature, with low concentrations of hypochlorite, leads to 2-phenylglyceric acid as the major product. This acid is formed by further oxidation of 1-phenyl-1,2-propanedione, which is an intermediate in the oxidation of propiophenone. Formation of this acid is reasonable in the light of other halogenation chemistry. Analogous reactions are observed for butyrophenone, which yields 2,3-dihydroxy-2-phenylbutanoic acid, and for cycloheptanone, which yields 1,2-dihydroxycyclohexanecarboxylic acid.Keywords: 2-phenylglyceric acid, propiophenone, chlorination, hydrolysis, rearrangement, cycloheptanone, 1,2-dihydroxycyclohexanecarboxylic acid.

ISSN:0008-4042    

DOI:10.1139/v91-275

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A total synthesis of (+/−) arthrographol (1) in seven steps from vanillin is reported. Key steps in the synthesis are a single-step conversion of 5-allylvanillin (2) into the benzofuranmethanol6, alkylation of the chloride25with the lithium anion of crotyl phenyl sulfide to give the sulfide26, and formation of the 1(E),3(E)-1,3-pentadienyl side chain of arthrographol (1) via oxidation of the sulfide26and subsequent elimination of phenylsulfenic acid. The synthetic (+/−) arthrographol (1) inhibits the growth ofOphiostomaclavigerum(Robin.-Jeff. & Davids.) Harrington, the most pathogenic of the fungi associated with the blue stain disease of lodgepole pine (PinuscontortaDougl. varlatifoliaEngelm.).Keywords: arthographol, alkylation, 2-butenyl phenyl sulfide, polyketide.

ISSN:0008-4042    

DOI:10.1139/v91-276

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The proton affinities (PAs) and deprotonation enthalpies (DPEs) were calculated for the pyranoid forms of two naturally occurring sugars,D-fructose andL-sorbose. In both molecules the PAs of the primary hydroxyl group (HO-1), the anomeric hydroxyl group (HO-2), and the ring-oxygen atom (O-6) were calculated, as were the DPEs of HO-1 and HO-2. The stabilities of the conjugate acids and bases of these sugars are enhanced by the presence of intramolecular hydrogen bonding, a feature that is significant in explaining the differences in sweetness and the rates of mutarotation of the title compounds, as well as the differences in the rates of acid-catalyzed hydrolysis of ketopyranosides.Keywords: proton affinity, deprotonation enthalpy,abinitiocalculations, AM1, hexuloses.

ISSN:0008-4042    

DOI:10.1139/v91-277

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The structures of five stabilized phosphonium ylides1–5were studied by1H,13C, and31P NMR. Various trapping experiments were followed by investigation of the relative reactivities of these ylides vis-à-vis benzaldehyde. A novel effect of some significance, the influence of acidic contaminants (conjugate acids, H2O, etc.) on the structure and reactivity of these compounds, is discussed.Keywords: stabilized phosphoranes, Wittig condensations, acid catalysis.

ISSN:0008-4042    

DOI:10.1139/v91-278

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A kinetic and ultraviolet–visible study of a series of thermo- and photochromic dyes is reported. Ultraviolet irradiation of the indolino-benzospiropyran derivatives1′–4′ leads to their transformation to the open-chain, colored merocyanine forms, which undergo thermal ring closure into the colorless spiro forms. The rate of this ring closure has been determined in different solvents. Plots of log (rate) vs. the solvent parameterETare linear but are dependent on the nature of the substituent in the phenyl moiety, which yields information on the electronic character of the ground state (IIa↔IIb) and the transition state. The ring-closure process is characterized by a zwitterionic type transition state, TS3. The merocyanine dyes exhibit a significant solvatochromic effect, which unexpectedly shows sensitivity to substituents on the phenyl group. This observation finds explanation through semi-empirical molecular orbital (MOPAC) calculations. The MOPAC calculations also predict that the most stable configurational isomer of the merocyanines is the CTTC form.Keywords: indolino-benzospiropyran–merocyanine interconversion, photochromic–solvatochromic dye

ISSN:0008-4042    

DOI:10.1139/v91-279

出版商:NRC Research Press    

年代:1991

数据来源: NRC