Hans Cerfontain

University of Amsterdam, Amsterdamo, North Holland, Netherlands

Are you Hans Cerfontain?

Claim your profile

Publications (294)211.69 Total impact

  • Source
    Peter De Wit, Hans Cerfontain, Alfred Fischer
    [Show abstract] [Hide abstract]
    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.
    Canadian Journal of Chemistry 02/2011; 63(8):2294-2297. · 1.01 Impact Factor
  • Hans Cerfontain, Ankie Koeberg-Telder
    [Show abstract] [Hide abstract]
    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.
    Canadian Journal of Chemistry 02/2011; 66(1):162-167. DOI:10.1139/v88-025 · 1.01 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Canadian Journal of Chemistry 02/2011; 72(9):1966-1971. DOI:10.1139/v94-251 · 1.01 Impact Factor
  • Peter de Wit, Hans Cerfontain
    [Show abstract] [Hide abstract]
    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.
    Canadian Journal of Chemistry 02/2011; 61(7):1453-1455. DOI:10.1139/v83-254 · 1.01 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Canadian Journal of Chemistry 02/2011; 62(11):2202-2205. DOI:10.1139/v84-376 · 1.01 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Canadian Journal of Chemistry 02/2011; 65(9):2234-2237. DOI:10.1139/v87-372 · 1.01 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Canadian Journal of Chemistry 02/2011; 71(2):210-215. DOI:10.1139/v93-031 · 1.01 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Canadian Journal of Chemistry 02/2011; 50(10):1591-1593. DOI:10.1139/v72-251 · 1.01 Impact Factor
  • ChemInform 12/2010; 24(49):no-no. DOI:10.1002/chin.199349112
  • H. R. W. ANSINK, H. CERFONTAIN
    [Show abstract] [Hide abstract]
    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.
    ChemInform 09/2010; 23(37):107-107. DOI:10.1002/chin.199237107
  • [Show abstract] [Hide abstract]
    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.
    ChemInform 09/2010; 24(36). DOI:10.1002/chin.199336102
  • [Show abstract] [Hide abstract]
    ABSTRACT: The UV spectra of the geometric isomers of the α-bis(methoxyimino)alkanes I-8 and the structurally related conjugated (methoxyimino)isoxazolines 11 and 13 all exhibit a ππ* absorption band, of which the maxima with cyclohexane as solvent are between 216 and 268 nm, and 258 and 282 nm, respectively. The differences in λmax are discussed in terms of variations in the degree of inter-iminyl conjugation, as a result of (i) variations in the inter-iminyl dihedral angle due to steric hindrance and (ii) variations in the ring strain and/or the dipolar repulsion of the two methoxyimino moieties, as with the three geometric isomers of the four-membered ring compound 1. The lower λmax of (E,E)-8 compared to (E,E)-4 is ascribed to a lower degree of cross-conjugation of the phenyl group with the planar α-bis(methoxyimino) chromophore in the former compound; the absorption band of (E,E)-8 is, in fact, similar to that of the aliphatic (E,E)-5. The energy of the ππ* absorption maximum of the (E,E)-α-bis(methoxyimino)alkanes appears to be linearly related to that of the corresponding (E)-α-oxo oxime ethers with a slope close to unity, illustrating that the sensitivity for structural variations is very similar for the two types of compounds.X-ray structure analysis showed the O-N = C-C = N-O chromophore of (E,E)-5, (E,E)-8 and the (hydroxyimino)isoxazoline (E)-10 in the crystalline state to be all planar within the limits of detection.
    09/2010; 111(1):41 - 48. DOI:10.1002/recl.19921110105
  • Frank Stunnenberg, Hans Cerfontain
    [Show abstract] [Hide abstract]
    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.
    09/2010; 111(2):79 - 87. DOI:10.1002/recl.19921110204
  • J. K. Bosscher, H. Cerfontain
    [Show abstract] [Hide abstract]
    ABSTRACT: The sulfonation of chlorobenzene and p-dichlorobenzene with sulfur trioxide in nitromethane as solvent has been studied. The main reaction products are arenesulfonic anhydride and probably arenepyrosulfonic acid. With p-dichlorobenzene as substrate the amount of diaryl sulfone is undetectably small; with chlorobenzene it is < 1-mole % relative to the converted substrate. The sulfonation is of the first order with respect to the substrate and of the second order with respect to sulfur trioxide. For each mole of converted substrate two moles of sulfur trioxide are consumed. The sulfonation of p-dichlorobenzene proceeds without a primary kinetic isotope effect of hydrogen.It is suggested that the sulfonation proceeds via 1-arenonium-1-sulfonate and 1-arenonium-1-pyrosulfonate as the subsequent reactive intermediates, with the formation of the latter intermediate as the rate-limiting step. The kinetics of the formation of 4,4′-dichlorodiphenyl sulfone are compatible with a mechanism in which the species p-ClC6H4S3O9H is the effective sulfonylating entity.The literature on aromatic sulfonation with sulfur trioxide in aprotic solvents is critically reviewed.
    09/2010; 87(8):873 - 887. DOI:10.1002/recl.19680870803
  • C. W. F. Kort, H. Cerfontain
    [Show abstract] [Hide abstract]
    ABSTRACT: Chlorobenzene has been sulfonated homogeneously in aqueous sulfuric acid varying from 83.4 to 99.6 wt-%, at 25°. The isomer distribution-98.8% para, 0.8% ortho, 0.4% meta - is constant over the acid range studied. The substrate isotope effect has been determined under conditions of rapid hydrogen exchange; kD/kH varies from 0.8 in 95% sulfuric acid to 0.4 in 97%. The dependence of the reaction rate and the isotope effect on the acid concentration is explained by an SE2-mechanism involving attack by H2S2O7 followed by proton removal from the σ-complex by HSO4−; the latter process is partly rate-limiting at high acid concentrations.
    09/2010; 86(8):865 - 872. DOI:10.1002/recl.19670860809
  • H. de Vries, H. Cerfontain
    [Show abstract] [Hide abstract]
    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.
    09/2010; 86(8):873 - 878. DOI:10.1002/recl.19670860810
  • H. Cerfontain, F. L. J. Sixma, L. Vollbracht
    [Show abstract] [Hide abstract]
    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.
    09/2010; 82(7):659 - 670. DOI:10.1002/recl.19630820704
  • H. Cerfontain, A. Telder
    [Show abstract] [Hide abstract]
    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.
    09/2010; 84(5):545 - 550. DOI:10.1002/recl.19650840502
  • A. J. Prinsen, H. Cerfontain
    [Show abstract] [Hide abstract]
    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.
    09/2010; 84(1):24 - 30. DOI:10.1002/recl.19650840104
  • [Show abstract] [Hide abstract]
    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.
    09/2010; 109(10):491 - 501. DOI:10.1002/recl.19901091002