Hans Cerfontain

University of Amsterdam, Amsterdamo, North Holland, Netherlands

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Publications (292)211.78 Total impact

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    Peter De Wit · Hans Cerfontain · Alfred Fischer
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    ABSTRACT: The mono- and di-sulfonation of the 1,8-alkano- and 1,8:4,5-dialkano-naphthalenes 1–5 with SO3 in dioxane and nitromethane as solvent have been studied and the results compared with those of 1,8-di- (6) and 1,4,5,8-tetramethylnaphthalene (7). The most reactive position of 1,8-ethano- (1), 1,8-propano-naphthalene (2), and 6 is the 4-position. Sulfonation adjacent to the 1,8-ethano bridge can be effected with SO3 in dioxane as reagent, whereas sulfonation ortho to the longer alkano bridges requires the more reactive reagent SO3 in nitromethane. Disulfonation of the1,8:4,5-dialkanonaphthalenes 3–5 leads to the predominant formation of the "noncrossed" (i.e. the 2,7-) disulfonic acid due to the substituent effect of the 2-sulfonic acid group. The isomer distribution data for the sulfonation of the arenes and their monosulfonic acids show that the steric hindrance increases in the order ethano propane ≤ butano and propane < peri dimethyl.
    Preview · Article · Feb 2011 · Canadian Journal of Chemistry
  • Hans Cerfontain · Ankie Koeberg-Telder
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    ABSTRACT: The methylation of a series of polymethylbenzenes (PoMB's) or their sulfonic acids by added hexamethylbenzene (HMB) and pentamethylbenzene-1-sulfonic acid (PeMB-1-S) as reagents in 95.5 and 98.4% H2SO4 as solvent has been studied under homogeneous conditions. HMB effects methylation of 2,4,6-trimethylbenzene-1-sulfonic acid (2,4,6-TrMB-1-S), 2,3,4,6-tetramethylbenzene-1-sulfonic acid (2,3,4,6-TeMB-1-S), and 2,3,5,6-TeMB-1-S, but not of the sulfonic acids of 1,3-dimethylbenzene (1,3-DMB), 1,2,3-TrMB, 1,2,4-TrMB, and 1,2,3,4-TeMB. PeMB-1-S is less reactive as methylating reagent than HMB. The observed substrate reactivity towards methylation by HMB was observed to decrease in the order , and towards methylation by PeMB-1-S to decrease in the order . On the basis of a comparison of these orders of substrate reactivities with those predicted for the series of the PoMB-1-sulfonates and the corresponding PoMB's, it is concluded that the substrate species undergoing methylation are the PoMB's and not the corresponding sulfonates.
    No preview · Article · Feb 2011 · Canadian Journal of Chemistry
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    Hans Cerfontain · Yousi Zou · Bert H. Bakker · Freek van de Griendt
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    ABSTRACT: The reaction of sulfur trioxide with benzene, the four halogenobenzenes, and six halogenonaphthalenes in dichloromethane as solvent, and with four chlorinated anthracenes in nitromethane as solvent, has been studied by analysis of the resulting mixture of the sulfo derivatives with 1H NMR. The sulfonation of benzene yields initially benzenesulfonic acid and subsequently the 1,3-disulfonic acid (1,3-S2). The initial sulfonation of the four halogenobenzenes yields ≥ 98% of the 4-S. Their subsequent sulfonation gives the 2,4-S2 and in the case of fluoro- and iodobenzene also the 2,4,6-S3. Monosulfonation of 1-fluoronaphthalene yields only the 4-S, whereas the three other 1-halogenonaphthalenese yield in addition some 5-S. Further sulfonation on any of the four 1-halogenonaphthalene-4-sulfonic acids yields a mixture of the 2,4-S2 and 4,7-S2, and eventually also some 2,4,7-S3, whereas the 1-halogeno-5-sulfonic acids give the corresponding 5,7-S2. Sulfonation of 2-chloro- and 2-bromonaphthalene yields initially 85% 8-S and 15% 4-S, which are subsequently converted into the 6,8-S2 and 4,7-S2, respectively. On reaction with 1.0 mol-equiv. of SO3, 2-chloroanthracene gives the 9-S, and 9-chloroanthracene gives an 18:82 mixture of the 4-S and 10-S. Both 1,5- and 1,8-dichloroanthracene yield initially the 4-S and subsequently the 4,8-S2 and 4,5-S2, respectively.
    Full-text · Article · Feb 2011 · Canadian Journal of Chemistry
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    ABSTRACT: This report describes the synthesis of β-hydroxy esters in good yields by reaction of α-aryl substituted ketones and phenylethanal with lithium methyl acetate and derivatives as anionoid reagents. The incomplete substrate conversion is ascribed to the enolate formation of the α-aryl carbonyl compounds, which concurrent reaction is negligibly small with aliphatic carbonyl compounds. The conversion of β-tetralone with lithium methyl acetate has been examined in some detail.
    Preview · Article · Feb 2011 · Canadian Journal of Chemistry
  • Hans Cerfontain · Cor Kruk · Roel Rexwinkel · Frank Stunnenberg
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    ABSTRACT: This study describes a method using 17O nmr to determine the intercarbonyl dihedral angle in a homologous series of seven 1,2-diketones. It is shown that the 17O nmr shifts of the 1,2-diketones are linearly dependent on both the electron density at the oxygen atoms and the n→π* excitation energy of the 1,2-diketo chromophore. Reduction of the overlap in the π system of the 1,2-diketo moiety leads to a gradual upfield shift of the 17O nmr signal, due to the increase in both the π-electron density at the oxygen atoms and the mean transition energy ΔE.
    No preview · Article · Feb 2011 · Canadian Journal of Chemistry
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    Peter de Wit · Hans Cerfontain
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    ABSTRACT: The sulfonation in 98.5% H2SO4 at 25.0 °C of naphthalene-1-sulfonic acid yields 58% 1,5-, 32% 1,6-, and 10% 1,7-disulfonic acids and that of the 2-sulfonic acid 4% 1,3-, 74% 1,6-, 18% 1,7-, and 4% 2,6- + 2,7-disulfonic acids. Further sulfonation of the latter disulfonic acid mixture in 105.2% H2SO4 at 25.0 °C yields 78% 1,3,6- and 12% 1,3,5- + 1,3,7-trisulfonic acids. Reaction of naphthalene-1,5-disulfonic acid with 105.2% H2SO4 at 25 °C yields 5-sulfonaphthalene-1-sulfonic anhydride.Partial rate factors for the sulfonation of naphthalene-1- and -2-sulfonate in highly concentrated aqueous sulfuric acid (where the sulfonating entity is H2S2O7) are reported. They are discussed in terms of the difference in the reactivity of the α- and β-positions of the naphthalene skeleton and the electronic and steric effects of the sulfonate substituent already present.
    Preview · Article · Feb 2011 · Canadian Journal of Chemistry
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    ABSTRACT: The sulfonation of benzene-SO2X (X = CH3, OCH3, OH, and Cl) and of 1- and 2-naphthalene-SO2X (X = CH3, OCH3, and Cl) with sulfur trioxide in nitromethane as solvent has been studied. In the benzene series, substitution only occurs at the 3-position irrespective of X; the reaction rates, which are all within the same order of magnitude, are low. Upon sulfonation of the 1-SO2X-substituted naphthalenes, the main sulfonation product (58–80%) is the 5-sulfonic acid (5-S); in addition, 6-S and small amounts of 3-S and 7-S are formed. Also, the formation of the intermolecular sulfonic anhydride of 1-(methylsulfonyl)naphthalene-5-S is observed. The 2-SO2X-substituted naphthalenes all yield the 5-S and 8-S in a ratio of For both the benzene and naphthalene series, insertion of SO3 between the SO2 and X moieties of the chlorosulfonyl and methoxysulfonyl substituents proper takes place. In the benzene series these reactions are fast as compared with the actual ring sulfonation, whereas in the naphthalene series they are, in general, relatively slow. In the naphthalene series the mesomeric directing effect of the SO2X groups is less important than in the benzene series; the "naphthalene α-effect" also plays an important role.
    No preview · Article · Feb 2011 · Canadian Journal of Chemistry
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    ABSTRACT: The kinetics of the sulfonation of phenylmethanesulfonic acid in 96.32–99.96% H2SO4 has been studied and partial rate factors for the —CH2SO3H substituent are reported.
    Preview · Article · Feb 2011 · Canadian Journal of Chemistry
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    No preview · Article · Dec 2010 · ChemInform
  • H. R. W. ANSINK · H. CERFONTAIN
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    No preview · Article · Sep 2010 · ChemInform
  • R. M. SCHONK · I. LEMBECK · B. H. BAKKER · H. CERFONTAIN
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    No preview · Article · Sep 2010 · ChemInform
  • Frank Stunnenberg · Hans Cerfontain
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    ABSTRACT: The photochemistry of the α-bis(methoxyimino)alkanes 1–5 and the, structurally related, conjugated dihydro(methoxyimino)isoxazoles 6 and 7 was studied. Triplet-photosensitized irradiation of 1–7 leads only to stepwise E-Z isomerization. Photostationary-state (pss) ratios for 1,6 and 7 are reported for the various applied triplet sensitizers. Direct irradiation with 254 nm leads to both E-Z isomerization (which is the dominant reaction) and formation of products resulting from initial N-O homolysis of the excited singlet ππ* state. Mechanisms for the formation of the various products are proposed and the relative importance of the various steps is indicated and discussed. For the α-bis(methoxyimino)alkanes 1 and 3, only the (E,Z)-isomer undergoes N-O homolysis. With the (methoxyimino)isoxazolines 6 and 7, only the exocyclic NO bond exhibits homolysis and not the strained endocyclic bond.
    No preview · Article · Sep 2010
  • C. W. F. Kort · H. Cerfontain
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    ABSTRACT: The mechanism of sulfonation in oleum proposed by Brand et al.3 - stepwise attachment of SO3 and H+ to the substrate, followed by the loss of the proton from the benzene ring - is shown to be inconsistent with the substrate isotope effects reported 3 by these authors. The sulfonation kinetics of p-di-, 1,2,3,4-tetra-, and penta-fluorobenzene in 97-109% sulfuric acid are discussed in terms of an extrapolation of the mechanism proposed recently 7 for aqueous sulfuric acid. In weak oleum — below 104% sulfuric acid — the rate-limiting step is
    No preview · Article · Sep 2010
  • H. de Vries · H. Cerfontain
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    ABSTRACT: The degree of ortho-substitution in the sulfonation of toluene, ethylbenzene and isopropylbenzene with sulfuric acid varying in concentration from 80.6 to 98.5% H2SO4 at 25° was determined. For a given sulfuric acid concentration the ratio of ortho- to (para- + meta-) substitution decreases with increasing size of the alkyl group, whereas for a given alkyl group this ratio decreases with decreasing sulfuric acid concentration. Partial rate factors for the homogeneous sulfonation of toluene, ethylbenzene, isopropylbenzene and t-butylbenzene in 86.3% sulfuric acid at 25° were calculated. The partial rate factors for ortho-substitution decrease with increasing size of the alkyl group, while those for para-substitution follow the Baker-Nathan order. Introduction of a sulfonic acid group ortho to the alkyl group of an alkylbenzene can be effected with weak oleum (∼ 16%) as reagent under conditions of disulfonation with toluene, ethylbenzene and isopropylbenzene, but not with t-butylbenzene.
    No preview · Article · Sep 2010
  • H. Cerfontain · F. L. J. Sixma · L. Vollbracht
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    ABSTRACT: The isomer distribution in the homogeneous monosulphonation of toluene in 77.6-98.8 wt- % aqueous sulphuric acid has been determined at various temperatures between 5 and 65°. Sulphone formation and disulphonation are negligible. The isomer distribution is independent of toluene conversion. The degree of meta-substitution is low under all conditions. At 25.0° the ratio of o- to p-toluene-sulphonic acid changes from 0.276 to 1.08 on varying the concentration of sulphuric acid from 77.6 to 98.8 wt-%; the meta-isomer shows only a small increase over this acid range. The decrease in the partial rate factor ratio, fp/fm, with increasing sulphuric acid concentration results mainly from an increase in the activation enthalpy difference between para- and meta-substitution. This decrease in fp/fm, is taken as an indication of increasing reactivity of the sulphonating entity. The entropy of activation is greater for para-substitution than for ortho-substitution. On varying the sulphuric acid concentration from 77.6 to 95.8 wt-%, the entropy difference decreases from 8.8 ± 0.2 to 4.8 ± 0.7 cal · degree-1 · mole-1 probably because the solvation of the transition state leading to ortho-substitution decreases with increasing acid concentration. The difference in activation enthalpy between para- and ortho-substitution is 1.3 ± 0.2 kcal · mole-1, whatever the acid concentration. This enthalpy difference is explained by an intramolecular hyperconjugative proximity effect in the transition state leading to ortho-substitution.
    No preview · Article · Sep 2010
  • H. Cerfontain · A. Telder · L. Vollbracht
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    ABSTRACT: The 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 : C6H6 ratio from 0.13 to 1.3. At a SO3 : C6H6 ratio > 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 of meta-substitution is low (1-5%) whereas that of para-substitution is high (∼ 80%). The difference in activation enthalpy between para- and meta-substitution is −2.7 ± 0.4 kcal · mole −1, that between para- and ortho-substitution 1.3 kcal · mole −1. The latter enthalpy difference is explainable by an intramolecular hyperconjugative proximity effect in the transition state leading to ortho-substitution. The entropy of activation is greater for para- than for ortho-substitution, indicating steric hindrance for ortho-substitution. The formation of sulfonic acid and sulfone is discussed in terms of the mechanism:
    No preview · Article · Sep 2010
  • H. Cerfontain · A. Telder
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    ABSTRACT: The solubility of benzene and toluene in aqueous sulfuric acid > 75 wt-% has been determined at 5, 25 and 45°. Molar heats of solution have been calculated. The benzene to toluene activity coefficient ratio is slightly greater than unity. The relatively large difference in activation entropy for sulfonation of the para-position in toluene and a single position in benzene1 is therefore attributed mainly to differences in solvation of the transition states.
    No preview · Article · Sep 2010
  • A. J. Prinsen · H. Cerfontain
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    ABSTRACT: The synthesis of a series of arylsulfonyl chlorides by a modification of the Sandmeyer reaction as developed by Meerwein et al1 is described. This method seems applicable to the preparation of arylsulfonyl bromides, but not for arylsulfonyl fluorides. The characteristic IR vibrations of the SO2-group are tabulated for the various arylsulfonyl halides.
    No preview · Article · Sep 2010
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    ABSTRACT: The (E)- and (Z)-isomers of the 3,3,n,n-tetramethyl-2-(methoxyimino)-1-cycloalkanones (n = 5 to 7) (3a-c) and their acyclic analogue (Z)-4-(methoxyimino)-2,2,5,5-tetramethyl-3-hexanone [(Z)-4] have been irradiated at λ 254 nm in acetonitrile as solvent in order to study the influence of ring size on product formation. The dependence of product composition on irradiation time revealed that the (E)-isomers of 3a-c undergo both E-Z isomerization and photodecomposition, whereas the (Z)-isomers undergo only Z-E isomerization. The primary step in photodecomposition is homolysis of the NO bond. The observed products result from the various possible reactions of initially formed methoxy and cyclic iminyl radicals 17, cyanoacyl radicals 18 formed by ring opening of 17, cyanoalkyl radicals 19 formed from 18 by decarbonylation and cyclopentaniminyl radical 20b, formed by cyclization of the 5-cyano-2-hexyl radical 19b. Mechanisms for the formation of the various products are proposed and the relative importance of the various steps is discussed, also in relation to the results obtained using carbon tetrachloride as radical scavenger.Irradiation of (Z)-4 at λ 254 nm leads to decomposition with formation of 2,2-dimethylpropanenitrile, methanol, isobutane and isobutene.
    No preview · Article · Sep 2010
  • Frank Stunnenberg · Roel Rexwinkel · Hans Cerfontain · A. Sevin
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    ABSTRACT: With the objective of understanding the photodissociation of cyclic s-cisoid α-oxo oxime ethers upon irradiation at λ 254 nm, an ab-initio study has been performed using s-cis-ethanedial monooxime as model compound. In accordance with previously presented experimental observations, the calculations demonstrated (i) that the initial step in the photodissociation is NO homolysis and (ii) that NO scission takes place with the (E), but not with the (Z) isomer, due to the presence of a relatively low-lying doubly excited (nπ*)(nπ*) state with the (Z) isomer, causing this isomer to decay via Z-E isomerization.
    No preview · Article · Sep 2010