Hans Cerfontain

University of Amsterdam, Amsterdam, North Holland, Netherlands

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Publications (267)53.41 Total impact

  • 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.
    Canadian Journal of Chemistry 02/2011; 61(7):1453-1455. · 0.96 Impact Factor
  • 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.
    Canadian Journal of Chemistry 02/2011; 66(1):162-167. · 0.96 Impact Factor
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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.
    Canadian Journal of Chemistry 02/2011; 63(8):2294-2297. · 0.96 Impact Factor
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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.
    Canadian Journal of Chemistry 02/2011; 62(11):2202-2205. · 0.96 Impact Factor
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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.
    Canadian Journal of Chemistry 02/2011; 65(9):2234-2237. · 0.96 Impact Factor
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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.
    Canadian Journal of Chemistry 02/2011; 71(2):210-215. · 0.96 Impact Factor
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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.
    Canadian Journal of Chemistry 02/2011; 72(9):1966-1971. · 0.96 Impact Factor
  • 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.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 111(2):79 - 87.
  • Hans Cerfontain, A. Koeberg‐Telder
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    ABSTRACT: NMR evidence is presented for complex formation between nitromethane and sulfur trioxide in thrichlorofluoromethane as solvent according to . In addition, kinetic evidence for complex formation between nitrobenzene and sulfur trioxide in trichlorofluoromethane was obtained from sulfonation studies of that system.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 89(6):569 - 574.
  • Hans Cerfontain, Jan A. J. Geenevasen
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    ABSTRACT: The photochemistry of 1-acetyl-3-methylbicyclo[1.1.0]butane in various solvents usingλ 254 and 300 nm radiation has been studied. In inert solvents, photoisomerization occurs with formation of 3 and 4 with subsequent photoconversion of 3 into 5. The (3 + 5)/4 ratios are significantly greater forλ 254 than forλ 300 nm radiation, illustrating direct reaction from the π* excited state(s). Additional photoreduction to 6 was observed forλ 300 nm in hydrogen-donating solvents, especially in diisopropyl ether and toluene. In carbon tetrachloride, atλ 300 nm, mainly the HCl addition compound 10 is formed via ketone-photosensitized decomposition of CCl4. Similarly, with methanol, 2-propanol and water as solvent or addendum, the 1,3-addition products 7–9 are obtained. Under all of these conditions, no photoproducts containing the intact bicyclo[1.1.0]butyl group were found, illustrating the high chemical reactivity of this severely strained group.Mechanisms for the formation of the photoisomerization, photoreduction and 1,3-dipolar addition products are proposed.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 105(10):386 - 394.
  • C. W. F. Kort, H. Cerfontain
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    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.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 86(8):865 - 872.
  • 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.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 86(8):873 - 878.
  • B. H. Bakker, R. M. Schonk, H. Cerfontain
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    ABSTRACT: Sulfonation of norbornene 1 with the SO3-dioxane complex affords the β-sultone 2, which rearranges at room temperature to the γ-sultone 3. Reaction of 1 with 2 equiv of SO3-nitromethane yields the carbyl sulfate 4. Carbocations are not involved in the formation of either the β-sultone or the carbyl sulfate.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 109(9):485 - 486.
  • J. J. I. Overwater, H. Cerfontain
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    ABSTRACT: Cyclopropanecarbaldehyde has been photolysed in the gas-phase with light in the 313 nm region at temperatures from 50 to 190 °C and at various aldehyde pressures. The most important gaseous reaction products are carbon monoxide, propene and cyclopropane. The quantum yield of propene, which is practically independent of temperature, decreases with increasing aldehyde pressure. The quantum yield of cyclopropane increases with both temperature and aldehyde pressure but decreases with increasing intensity of the absorbed light.It is proposed that propene is formed by intramolecular decomposition of singlet excited cyclopropanecarbaldehyde, whereas cyclopropane ultimately results from a radical decomposition of triplet cyclopropanecarbaldehyde.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 87(1):73 - 85.
  • A. Koeberg‐Telder, Hans Cerfontain
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    ABSTRACT: Sulfonation of anthracene-9-d with sulfur trioxide-dioxane in dioxane as solvent at 40° leads to 31 ± 2% α-, 8 ± 2% β- and 61 ± 2% meso-substitution. The substitution at the meso-position proceeds with a maximal substrate kinetic isotope effect of hydrogen - kH/kD = 6.8 with 5.6 and 8.6 as limiting values - indicating that the proton removal from the σ-complex is rate-limiting.From the data for anthracene-9-d it was calculated that the sulfonation of C14H10 leads to 21 ± 3% 1-, 6 ± 2% 2- and 73 ± 5% 9-substitution.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 91(1):22 - 32.
  • Margareth J. C. M. Koppes, Hans Cerfontain
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    ABSTRACT: The photochemical rearrangement of the two 2-(2-alkenyl)-2-(1-cyclopentenyl)cyclopentanones (E)-1a and (E)-2a have been studied under conditions of both direct (λ 300 nm) and tripletsensitized irradiation in order to determine the applicability of 2-alkenyl moieties as intramolecular quenchers of the lowest excited triplet states of the β,γ-enone chromophore.The β,γ·γ′,δ′-dienone (E)-1a, upon direct irradiation, exhibits a reversible 1,3-acyl shift (1,3-AS) leading to an eventual photostationary state {[(E)-1a]/[(E)-1b]}pss = 4.0 ± 0.8, whereas triplet photosensitization of (E)-1a gives the ODPM isomer (E)-1c. Both processes occur without (E)-(Z) isomerization of the 2-butenyl side-chain. Direct irradiation of (E)-2a yields, albeit very inefficiently, the 1,3-AS compound (E)-2b (Φ < 0.001) as the primary product which, upon electronic excitation, forms, in competing reactions, (E)-2a (Φ = 0.18) and (Z)-2b (Φ = 0.035). Upon triplet photosensitization of both (E)-2a and (E)-2b, only (E)-(Z) isomerization of the styryl side-chain is observed. The eventual photostationary state in the direct irradiation equals {[(E)-2a]/[(Z)-2a]/[(E)-2b]/[(Z)-2b]}pss=(33± 1)/(33 ± 1)/(17 ± 1)/(17 ± 1).The differences in photochemical behaviour of the β,γ·γ′,δ′-dienone substrates and their 1,3-AS products are discussed with special emphasis being placed upon the triplet energies of the 2-alkenyl chromophores relative to those of the β,γ-enone chromophores and the occurrence of CT interaction which enhances the internal conversion of the S1(nπ*) states of the β,γ-enone chromophores.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 104(10):272 - 276.
  • Paul L. Verheijdt, Hans Cerfontain
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    ABSTRACT: A series of α,α,ω,ω-tetramethyl-1,2-cycloalkanediones, with a ring size varying between 4 and 8 C atoms (la-e), together with 2,2,5,5-tetramethyl-3,4-hexanedione (2a), have been irradiated both in 2-propanol and in benzene in order to study the influence of the diketo conformation on the photochemical behaviour of 1,2-diketones. Irradiation of lb-d in 2-propanol leads exclusively to photoreduction with formation of the corresponding acyloins via intermolecular H abstraction, whereas le and 2 yield predominantly the 2-hydroxycyclobutanone product via intramolecular H abstraction. The irradiations of la-e in benzene lead to different products for the six homologous cyclic 1,2-diketones. Mechanisms for the formation of the various products are proposed. It is concluded that the 1,2-diketones with Φ (ground state) <90° and >90° react, upon excitation, from a conformation having a planar cisoid and transoid diketo geometry, respectively.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 102(3):173 - 181.
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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.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 109(10):502 - 508.
  • H. Cerfontain, A. Telder
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    ABSTRACT: The kinetic isotope effect of hydrogen in the sulfonation of benzene with sulfur trioxide in nitrobenzene as solvent has been determined at 25° in a competitive study as kH/kD = 1.35 ± 0.16; for nitromethane as solvent kH/kD = 1.25 ± 0.01. Small amounts of diphenylsulfone were obtained as by-product in the sulfonation reactions. For the sulfonylation reaction in the two solvents the kinetic isotope effect was determined at 25° as kH/kD = 0.96 ± 0.04 and 0.94 ± 0.07 respectively.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 84(12):1613 - 1616.
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    ABSTRACT: Photochemical E-Z isomerization of 2-(methoxyimino)-1-indanone (1) and its 7-methyl derivative (2) was studied under conditions of direct irradiation (λ 350 and 300 nm) and triplet photosensitization. The decay ratios k5/k6 for triplet photosensitization and direct irradiation at λ 350 nm are the same for a given compound, indicating that isomerization of the studied -oxo oxime ethers upon direct irradiation at λ 350 nm also proceeds from the (lowest) excited triplet state. Upon direct irradiation at λ 300 nm, the photostationary state (pss) was found to depend on the concentration of the 2-(methoxyimino)-1-indanone: at high concentrations, the (E)-isomer strongly dominates (>90%), whereas, at low -oxo oxime ether concentrations, a substantial amount of the (Z)-isomer is present (up to 35%). The concentration dependence of the pss is explained in terms of excimer formation of the S2(ππ*) state, the excimer being capable of inducing efficient E-Z isomerization with a different decay ratio than that of the excited triplet monomer.
    Recueil des Travaux Chimiques des Pays-Bas. 09/2010; 109(11):531 - 536.