摘要:

AbstractSeveral O‐isopropylidene derivatives of gymnemagenin (5), a hexahydroxytriterpene from the leaves ofGymnema sylvestreR. Br. have been prepared, which may perhaps be useful to correlate gymnemagenin with other triterpenes. From the data obtained we conclude that gymnemagenin is 3β, 16β, 21β, 22α, 23, 28‐hexahydroxy‐ole

ISSN:0018-019X    

DOI:10.1002/hlca.19690520202

出版商:WILEY‐VCH Verlag GmbH    

年代:1969

数据来源: WILEY

摘要:

AbstractA graphical procedure for the evaluation of association equilibria in solution is given. It consists of families of master plots that are superimposed on a diagram of experimental values (namely practical osmotic coefficientvs.concentration). Different models (dimerisation, multimerisation, chain association) can be tested, and the values of up totwoassociation constants can be read off. Tables of the normalized variables and various examples are presented.

ISSN:0018-019X    

DOI:10.1002/hlca.19690520203

出版商:WILEY‐VCH Verlag GmbH    

年代:1969

数据来源: WILEY

摘要:

Abstract2‐(2‐hydroxyphenyl)‐4‐carboxy‐naphtho [1.2‐d] triazoles are terdentate ligands which can form 1:1 complexes with CuIIand NiIIions, and 1:1 as well as 1:2 complexes with CrIII‐ions. All these complexes are characterized byortho‐condensed 6/6‐membered rings, the 1:2 chromium complexes having the DREW‐PFITZNERarrangement. This behaviour, which differs from that of comparableo‐hydroxy‐o′‐carboxy‐diaryl azo‐dyestuffs, is due to the different dim

ISSN:0018-019X    

DOI:10.1002/hlca.19690520204

出版商:WILEY‐VCH Verlag GmbH    

年代:1969

数据来源: WILEY

摘要:

Abstract(S)‐α‐Amino‐δ‐nitropentanoic acid (δ‐nitro‐L‐norvaline), an intermediate of the total synthesis of ferrichrome, was synthesized starting from diethyl oxalate and

ISSN:0018-019X    

DOI:10.1002/hlca.19690520205

出版商:WILEY‐VCH Verlag GmbH    

年代:1969

数据来源: WILEY

摘要:

AbstractBy thermal isomerization of the 3‐oxa‐6.7‐diphenyl‐tetracyclo [3.2.0.02, 7. 04, 6]‐heptane‐1. 5‐dicarbomethoxylate (4) besides the oxanorbornadiene 3 and the hydroxy‐fulvene 7, the ‘stable’ benzeneoxide 7‐oxa‐2.5‐diphenyl‐bicyclo [4.1.0]hepta‐2.4‐diene‐3.4‐dicarbomethoxylate (5) has been isolated. In the temperature range −50 to 170°C no equilibration with the

ISSN:0018-019X    

DOI:10.1002/hlca.19690520206

出版商:WILEY‐VCH Verlag GmbH    

年代:1969

数据来源: WILEY

摘要:

AbstractTo prove the chemical structure of metabolites of the antidepressant drug (dimetacrin2) (Istonil®3), 2‐ and 3‐hydroxy‐9,9‐dimethyl‐10‐dimethylaminopropyl‐acridane and 2‐hydroxy‐monometacrin4were synthesized using substituted alkoxy diphenylamines (V) as intermediates. The methoxy compounds on treatment with strong acids cyclized either to the corresponding acridanes or to their O‐demethylated derivatives, VI (X  OCH3or OH), depending on concent

ISSN:0018-019X    

DOI:10.1002/hlca.19690520207

出版商:WILEY‐VCH Verlag GmbH    

年代:1969

数据来源: WILEY

摘要:

Abstract2‐Dimethylaminoethanol reacts with 1,2‐epoxyoctane presumablyviaa hydrogen‐bonded complex to form a quaternary ammonium compound which exhibits a fair stability at lower temperatures. At higher temperatures the quaternary structure decomposes with the resulting formation of a wide variety of products. Most of the products have been identified and a reasonable mechanistic picture for their formation is presented. The main products of the reaction are 1‐(ß‐dimethylaminoethoxy)‐2‐octanol (IIIa) and 1‐dimethylamino‐2‐octanol (IV), the latter being formed according to several pathways concurrently with ethylene oxide, 2‐methyl‐4‐hexyl‐1, 3‐dioxolane (VI), and 2‐hexyl‐1, 4‐dioxane (VII). Some of the higher molecular weight products are secondary products resulting from the action of epoxide on the primary reaction products IIIa and IV. The relative amount of each product formed depends on the ratio of starting materials and reaction temperature. In the presence of an additional hydroxylic solvent such as ethanol, the s

ISSN:0018-019X    

DOI:10.1002/hlca.19690520208

出版商:WILEY‐VCH Verlag GmbH    

年代:1969

数据来源: WILEY

摘要:

AbstractThe enthalpies of formation of 1.6‐methano‐[10] annulene (IV) (ΔHf298(IV,g) = 75.2 ± 0.6 kcal mol−1), 1.6‐imino‐[10] annulene (V) (ΔHf298(V,g) = 87.8 ± 0.7 kcal mol−1) and of 1.6‐oxido‐[10] annulene (VI) (ΔHf298(VI,g) = 47.8 ± 1.2 kcal mol−1) have been determined by combustion calorimetry. The difficulties connected with an attempt to derive meaningfull «resonance

ISSN:0018-019X    

DOI:10.1002/hlca.19690520209

出版商:WILEY‐VCH Verlag GmbH    

年代:1969

数据来源: WILEY

摘要:

AbstractThe kinetics of the reduction of substituted azobenzenes by dihydroquinoxalines have been measured. Azo‐compounds with electron‐donating substituents ino‐ orp‐position are reduced to the amines in neutral or acid solution, whereby two molecules of the reducing agent are consumed. If such substituents are absent, the reaction stops at the hydrazo stage. This is also the case with cleaveable azo‐compounds in strongly alcaline solution.Our kinetic measurements of the reductive cleavage reaction of methylorange are in agreement with only one mechanism, which is discussed in detail. The very high reactivity of protonated methylorange may be attributed to the formation of a mesomeric quinoid structure. Knowing the pH‐dependence of the reaction rate allows the determination of the pK‐value of the extremely unstable hydrazo stage of methylorange. The structure of the dihydroquinoxaline has a strong influence on ΔH‡ and ΔS‡, and therefore o

ISSN:0018-019X    

DOI:10.1002/hlca.19690520210

出版商:WILEY‐VCH Verlag GmbH    

年代:1969

数据来源: WILEY

摘要:

AbstractThe composition of equilibrated gaseous mixtures of 3‐methylene‐1,5,5‐trimethylcyclohexene (MTC) and 1,3,5,5‐tetramethyl‐1,3‐cyclohexadiene (TECD) have been measured for temperatures ranging between 302 and 410°C. Nitrogen oxide was used as catalyst. Equilibrium was approached from either side. The least squares regression analysis of the observed temperature dependence of the equilibrium constantsK1.2=k1/k2= (TECD)eq./(MTC)eq.yields (with standard errors)\documentclass{article}\pagestyle{empty}\begin{document}$$ \log K_{1.2} = (0.35 \pm 0.2) - (0.5 \pm 0.3)/4.58 \times 10^{- 3} T(^ \circ {\rm K)}{\rm .} $$\end{document}This results in ΔH1.2(300°K) = 0.4 ± 0.3 kcal/mole and ΔS1.2(300°K) = 1.4 ± 0.8 cal/°‐mole. The fact that the reaction is practically thermoneutral implies that the secondary, «biallylic» CH bond in MTC is equally strong as the primary «biallylic» CH bond of the 1‐methyl group in TECD.The observed enthalpy and entropy differences between the two isomers are in agreement with prediction based on the concept of additivity of thermodynamic increment properties (ref. [5]). The results of this work also yield a value of 23.7 cal/°‐mole for the entropy contribution characteristic of the 1,3‐cyclohexadiene ring structure. When combined with the ARRHENIUSparameters, reported earlier [1] fork1, the results of this work yield for the back reaction logk2(1/

ISSN:0018-019X    

DOI:10.1002/hlca.19690520211

出版商:WILEY‐VCH Verlag GmbH    

年代:1969

数据来源: WILEY