摘要:

AbstractThe sulfonation of benzene and toluene with sulfur trioxide without solvent has been studied extensively.With benzene at low conversion benzenesulfonic acid and diphenylsulfone are the only products. At 25° the sulfone: sulfonic acid ratio changes from 0.2 to 0.6 on varying the SO3: C6H6ratio from 0.13 to 1.3. At a SO3: C6H6ratio>1.3 benzene‐1,3‐disulfonic acid and diphenylsulfonesulfonic acid are found among the reaction products as well. With toluene the sulfone formation is less than with benzene.The isomer distribution of the monosulfonic acids formed in the sulfonation of toluene has been determined at various temperatures between −44 and 65°. Under all conditions the degree ofmeta‐substitution is low (1‐5%) whereas that ofpara‐substitution is high (∼ 80%). The difference in activation enthalpy betweenpara‐ andmeta‐substitution is −2.7 ± 0.4 kcal · mole−1, that betweenpara‐ andortho‐substitution 1.3 kcal · mole−1. The latter enthalpy difference is explainable by an intramolecular hyperconjugative proximity effect in the transition state leading toortho‐substitution. The entropy of activation is greater forpara‐ than forortho‐substitution, indicating steric hindrance forortho‐substitution.The formation of sulfonic acid and sulfon

ISSN:0165-0513    

DOI:10.1002/recl.19640831102

出版商:WILEY‐VCH Verlag    

年代:1964

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19640831103

出版商:WILEY‐VCH Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractFor our investigations of model compounds related to the active site of esterases some new peptide derivatives containing the amino acid sequences gly‐asp‐ser‐gly, gly‐glu‐ser‐gly and gly‐gly‐ser‐gly were synthesized. The compounds were obtained by coupling two dipeptide derivatives using the mixed anhydride procedure. The azide method was used to prepare the dipeptide derivatives. The products thus obtained possessed the L‐L configuration. Some physical data, including the dissociation constan

ISSN:0165-0513    

DOI:10.1002/recl.19640831104

出版商:WILEY‐VCH Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractIl est montré que dans la réaction de Friedel‐Crafts d'acétylation de l'o‐ et dum‐bromofluorobenzène, le groupement acétyle occupe la positionparapar rapport au fluor; dans la même réaction avec lep‐bromofluorobenzène, le groupement acétyle occupe la positionorthopar rapport au brome. Ces résultats sont parallèles à ceux obtenus auparavant sur les c

ISSN:0165-0513    

DOI:10.1002/recl.19640831105

出版商:WILEY‐VCH Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractOptically active 1‐phenylethyl chloride or bromide when treated with a solution of lithium, sodium, or potassium in liquid ammonia yields optically active 2,3‐diphenylbutane. It is concluded that the formation of the “biaralkyl” proceedsviacarbanions.The absolute configurations of (+)‐ and (‐)‐2,3‐diphenylbut

ISSN:0165-0513    

DOI:10.1002/recl.19640831106

出版商:WILEY‐VCH Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractAromatization of 3‐ketotetrahydrothiophen enamines (II) furnishes 3‐dialkyl‐aminothiophens (III). Reduction of the enamines with formic acid yields the tetrahydro derivatives (V). These compounds represent the first examples of simple 3‐tert‐amino‐thiophens and ‐tetrah

ISSN:0165-0513    

DOI:10.1002/recl.19640831107

出版商:WILEY‐VCH Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractTritylation ofN‐methyl‐para‐toluidine,N‐ethyl‐para‐toluidine, andN‐methyl‐para‐chloroaniline resulted in theN‐trityl derivatives of the corresponding aromatic primary amines. The tritylation thus was accompanied by a dealkylation.N‐trityl‐N‐methyl‐para

ISSN:0165-0513    

DOI:10.1002/recl.19640831108

出版商:WILEY‐VCH Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractTwo simple calciferol analogues (1) having no five‐membered (D) ring fused to the C ring, show the same smooth thermal isomerisation to the corresponding precalciferol analogues as calciferol itself. The kinetics of this reaction have been studied; the activation energy and entropy were found to be 21.6 (± 0.2) kcal/mole and −17.2 e.u., respectively. The insensitivity of the reaction towards even rather drastic changes in the conditions is striking and the reaction mechanism formerly given10, 15for the vitamin D ⇆ previtamin D interconversion seems to remain an attractive working hypothesis.There is one difference between the analogues and the calciferol system itself; in the former the equilibrium is far more on the “precalciferol” side. It is argued that this difference (and perhaps also the relative long wavelength ultra‐violet absorption of precalciferol) may be due to a strain in the precalciferol molecule originating from the presence of the C8‐C9double bond in combination with thetransfused five‐membered ring. In agreement herewith, 13α‐precalciferol analogues having the five‐membered ringcis‐bonded and lacking this strain, are found to show a position of the equilibrium (and an ultra‐violet absorption) similar to that of the analogue II and different f

ISSN:0165-0513    

DOI:10.1002/recl.19640831109

出版商:WILEY‐VCH Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractNew three‐step syntheses of cis‐bicyclo[3.3.0]octane and cis‐bicyclo[3.3.0]oct‐2‐ene are described; overall yields of about 20% based on cyclopentadiene are

ISSN:0165-0513    

DOI:10.1002/recl.19640831110

出版商:WILEY‐VCH Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractA general method is described for synthesizing compounds of structure exemplified by A, from methyl isocyanate and 2‐hydroxybenzaldehyde in thepresence of a basic catalyst (triethylamine).The reaction product of phenyl isocyanate and 2‐hydroxybenzaldehyde in the presence of triethylamine is 3,4‐dihydro‐3‐phenyl‐4(phenylcarbamoyloxy)‐2H‐1,3‐benzoxazin‐2‐one (structure B).Evidence for the proposed structures is presented based on chemical an

ISSN:0165-0513    

DOI:10.1002/recl.19640831111

出版商:WILEY‐VCH Verlag    

年代:1964

数据来源: WILEY