摘要:

The kinetics of the Oxidation of several sodiump-alkylbenzenesulfonates by aqueous dichromate have been studied under slightly acidic conditions (pH = 7.0 to 5.4). The results indicate that the only active oxidant under these conditions is the acid chromate ion, HCrO4−, and that the reaction probably involves a free radical process.

ISSN:0008-4042    

DOI:10.1139/v71-461

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The1H n.m.r. spectra of 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (4), of 1,2:5,6-di-O-isopropylidene-α-D-allofuranose (5), and of their 3-O-acetyl derivatives6and7, respectively have been separately measured in the presence of varying concentrations of the tris {dipivaloylmethane} derivatives of europium (1), thulium (2), and praseodymium (3). For these derivatives, both europium (1) and thulium (2) induce shifts to low field whereas praseodymium (3) produces high field shifts; for any individual proton the magnitude of the induced shift is shown to be linearly proportional to the amount of added reagent and is best followed by addition of volume aliquots of a dilute solution of the lanthanide. It is shown that simplistic rationales concerning the relationship between the magnitudes of induced shifts and the geometry of the substrate system can be entirely misleading; theD-gluco-derivative4is particularly noteworthy in this regard. Since the magnitudes of the induced shifts are temperature dependent it is important to report the temperature at which experiments are performed. For1the induced shifts areca. 2.2 times larger for carbon tetrachloride solutions than for deuterochloroform solutions when operating under otherwise identical conditions.

ISSN:0008-4042    

DOI:10.1139/v71-462

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The n.m.r. line-broadening method was used to measure rates of hydrogen exchange in the 2,4,6-trihydroxybenzenonium ion (carbon-protonated phloroglucinol) in a series of concentrated sulfuric and perchloric acid solutions. Comparison of separately determined rates of exchange of protons in the methylene and vinyl groups of this ion allows a concerted mechanism for the exchange reaction to be excluded and shows that exchange must occur through intermediate formation of completely deprotonated 1,3,5-trihydroxybenzene. This assignment of reaction mechanism allows transformation of the data into deprotonation rate constants, which, together with previously measured positions of equilibrium, permit estimation of specific rates of protonation of 1,3,5-trihydroxybenzene,k+; the latter are in good agreement with the rate of aromatic hydrogen exchange of 1,3,5-trihydroxybenzene measured by an isotopic tracer method at lower acidities. The kinetic acidity dependence ofk+is unusually shallow; this, coupled with the much steeper acidity dependences of other aromatic protonation reactions, serves to reinforce the growing realization that there is no unique relationship between kinetic acidity dependence and reaction mechanism.

ISSN:0008-4042    

DOI:10.1139/v71-463

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The electrophilic substitution ofN-alkylated isocarbostyrils was examined in considerable detail. Bromination, acylation, nitration, and acid-catalyzed condensation with formaldehyde occurred exclusively at C-4 under relatively mild conditions. The acylation of isocarbostyrils has heretofore not been reported.The bromination of 2-methyl-5-nitroisocarbostyril in aqueous acetic acid gave 2-methyl-3,4-dihydro-3-hydroxy-4-bromo-5-nitroisocarbostyril (7) of unknown stereochemistry, as the sole product. When heated above its melting point,7lost the elements of water to give the "normal" product of bromination8.In aqueous acetic acid, excess bromine was shown to convert isocarbostyrils to the corresponding 3,4-dihydro-3-hydroxy-4,4-dibromo derivatives whose structures were supported by spectral and degradative evidence.

ISSN:0008-4042    

DOI:10.1139/v71-464

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The sulfuric acid catalyzed acylation of 2-methyl-5-nitroisocarbostyril with carboxylic acid anhydrides gave the corresponding 4-acylated derivatives3, which underwent reductive cyclization to 2-substituted derivatives of 4-methyl-1,3,4,5-tetrahydropyrrolo[4.3.2.de]isoquinolin-5-one (4). Alkaline hydrolysis of the six-membered lactam in4was accompanied by a retro-Mannich reaction to produce 2-substituted indole-4-carboxylic acids in about 40 % overall yield from3.

ISSN:0008-4042    

DOI:10.1139/v71-465

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Exact thermodynamic analysis of the Hammett equation has led to four differential equations relating δΔH0, δΔS0, δΔCp0, dρ/dT, and d2ρ/dT2. Similar equations can be obtained in terms of activation parameters ΔH≠, etc. For temperature independent δΔH0and δΔS0and therefore δΔCp0 = 0, two of these differential equations lead to ρ = ρ∞[1–(β1/T)] and the familiar isoequilibrium (isokinetic) equation δΔH0 = β1δΔS0. The "isoequilibrium (isokinetic) temperature" represented here by β1is a temperature independent constant of integration. For constant non-zero δΔCp0we similarly obtain more complicated expressions for ρ and the "isoequilibrium (isokinetic) temperature." These findings are considered in relation to a model in which environmental contributions (due to solute–solvent interactions) to δΔH0and δΔS0are related by a parameter βc. The relationship between β1, and βcis established, and it is shown that in general β1 ≠ βc.

ISSN:0008-4042    

DOI:10.1139/v71-466

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

121Sb Mössbauer data are presented for NaSbF4, KSbF4, KSb2F7, K2SbF5, KSbF6, CsSb2F11, and (NH4)2SbCl5. Attempts are made to rationalize the data in terms of known structural parameters.

ISSN:0008-4042    

DOI:10.1139/v71-467

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The thermal analyses of hexahydroxystannates of bivalent metals of the type Me[Sn(OH)6], where Me = Zn, Co, Cu, Ni, Mn, Ca, Mg, Cd, Sr, reveal that the primary mode of decomposition occurs by dehydroxylation and subsequent decomposition of the metastannate residue occurs in the Zn, Cu, Mn, Ca, and Mg compounds. Calorimetric measurements along with related enthalpic values for the decomposition reaction are given. The kinetics of thermal decomposition of all compounds studied, except the Cd and Mg analogues, follow first order reaction kinetics up to α ~ 0.9.

ISSN:0008-4042    

DOI:10.1139/v71-468

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The influence of dimethyl sulfoxide (DMSO), diethyl sulfoxide (DESO), tetramethylene sulfoxide (TMSO), and tetramethylene sulfone (TMSO2) on the temperature of maximum density of water bas been investigated. It is concluded that in dilute solution DESO stabilizes the characteristic three-dimensional structure of water. The other solutes, however, destabilize the structure of water over the entire concentration range studied (0–1.3 × 10−2mole fraction solute).

ISSN:0008-4042    

DOI:10.1139/v71-469

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

An investigation of the rate of decomposition of aqueous sodium bromite is described. The main reactions are: 2BrO2− → BrO− + BrO3− and Br− + BrO2− → 2BrO−, followed by BrO− + BrO2− → Br− + BrO3−. The rate constants and activation parameters of the decomposition reactions are reported. As the second reaction is the reverse of that previously studied in the decomposition of sodium hypobromite, its equilibrium constant (at various temperatures) can be obtained, and hence the thermodynamic properties of aqueous bromite ions. These are briefly compared with the properties of similar ions containing bromine or chlorine.

ISSN:0008-4042    

DOI:10.1139/v71-470

出版商:NRC Research Press    

年代:1971

数据来源: NRC