Showing papers in "Recueil des Travaux Chimiques des Pays-Bas in 1972"

Formation of dialkylthiophenes by thermolysis of di(1-alkenyl) disulfides and alkyl 1-propenyl disulfides

Abstract: 3,4-Dialkylthiophenes are formed in good yields by heating di(1-alkenyl) disulfides at 150-200° in the presence of potassium hydrogen sulfate. Thermolysis of alkyl 1-propenyl disulfides gives mixtures of sulfur-containing compounds, consisting mainly of 3,4-dimethylthiophene, dialkyl disulfide, alkyl and 1-alkenyl monosulfides, and dialkyl trisulfide.

Chemistry of sulfines. XII: Cyclo‐addition reactions with dienes

Abstract: The cyclo-addition reaction of sulfines with 1,3-dienes is described. In all cases studied six-membered ring sulfoxides were formed (Schemes I, II and III). Sulfines with electron-withdrawing substituents, such as dichlorosulfine, appeared to be very reactive dienophiles. The stereochemistry of the reaction was studied with Z- and E-chloro-phenylsulfine and 2,3-dimethyl-1,3-butadiene. The results show that the stereochemical configuration of the starting sulfine is predominantly retained in the (2 + 4) cyclo-adduct.

Activity coefficients of single ions III: The difference between the standard chemical potentials of single ions in methanol and methanol-water mixtures and in water at 25°C, and some related quantities

Abstract: The method described by De Ligny et al. for the estimation of activity coefficients of single ions, which originated from ideas of Alfenaar and De Ligny, Buckingham, Halliwell and Nyburg and Muirhead-Gould and Laidler, has been improved further. The modified method was applied successfully to the transfer of ions from water to methanol and methanol-water mixtures. A similar method was used to estimate the standard partial molar enthalpy of transfer ΔH° of single ions, and from these data values for the standard partial molar entropy of transfer ΔS° were obtained. The differences between the standard real potentials of the chloride ion in methanol and methanol-water mixtures, and in water have been determined by Case and Parsons. From these data, the corresponding differences for the standard chemical potentials and the surface potential of water, the surface potentials of methanol and methanol-water mixtures, were determined.

Activity coefficients of single ions (V) in acetone and acetone-water mixtures

Abstract: A method for the estimation of standard chemical potential differences (Δμ°) of single ions for the transfer from one solvent to another, described previously, is further improved and applied to the transfer from water to acetone and acetone-water mixtures. With some reservation a value of the surface potential χ of acetone is derived.

Formation and PMR spectra of arene dipositive ions

Abstract: Perylene, naphthacene, anthracene and some substituted anthracenes are oxidized to the dipositive ions by SbF5 (neat or in SO2CIF). In FSO3H-SbF5 dication formation takes only place with the easily oxidizable arenes perylene and naphthacene. The dication of anthracene has also been obtained by bromide abstraction from 9, 10-dibromo-9, 10-dihydroanthracene. The PMR spectra of the dications are reported. Like in the dianions, the sum of the charge-induced shifts varies considerably from one arene to the other.

Solutes in sulfuric acid 4: Ionization of arenesulfonic acids; determination of pKa values by UV techniques

Abstract: The ionization of several aromatic sulfonic acids in aqueous sulfuric acid has been measured by means of UV techniques. The sulfonic acid ionization does not follow the aniline Ho acidity function, but the benzophenone Hao and the HA acidity functions. On the basis of the Hao scale, the pKa of benzenesulfonic acid is −6.65 ± 0.05. Substituent effects on the ionization of the sulfonic acid group are small; the Hammett ρ-value was estimated to be 0.7 ± 0.2.

Vibrational spectra and structure(s) of X(OR)4 molecules with X C,: Si and R = methyl, ethyl

Abstract: Vibrational spectra of tetramethoxymethane (TMM), tetraethoxymethane (TEM), tetramethoxysilane (TMS) and tetraethoxysilane (TES) have been recorded and assigned. DTA curves and temperature vs. time curves have been recorded in the region −150 to + 30°. No transition points have been observed, melting ranges are −1 to +2 (TMM); −16 to −12 (TEM); +10 to +16 (TMS) and −71 to −68° (TES). The liquid state of tetramethoxymethane (TMM) contains two rotamers; the skeleton C(OC)4 may have S4 or D2d symmetry. The S4 form is about 1 kcal/mole more stable than the D2d form of TMM in the liquid. Solid TMM consists probably of the D2d configuration only. There is no distinction between either configuration in tetramethoxysilane (TMS) as the rotation of methoxy groups around their SiO axes is apparently free for practical purposes. The methyl group of an ethoxy group in X(OC2H5)4 may occupy a gauche or a trans position relative to its XO bond. Rotational isomerism of this kind is probably present in tetraethoxymethane (TEM). Rotational isomerism is probably absent in tetraethoxysilane (TES).

A convenient synthesis of L‐1‐methylhistidine and L‐1‐ethylhistidine

Abstract: Alkylation of the easily accessible methyl ester of L-Na,3-dibenzoylhistidine with the aid of trimethyl- and triethyloxonium fluoroborate followed by decomposition with water and acid hydrolysis yielded L-1 -methyl- and L-1-ethylhistidine respectively. Comparison with natural L-1-methylhistidine confirmed the structure and optical purity.

The interaction between polyethyleneimine and sodium dodecyl sulfate in water

Abstract: The amount of sodium dodecyl sulfate bound by polyethyleneimine is measured under varying concentrations of the reactants and additional ions, in particular H+ ions. The results can be interpreted consistently as the formation of uncharged complexes between the negatively charged dodecyl sulfate ions and the positively charged monomeric groups of the polyethyleneimine molecule.

The coordination chemistry of phosphoryl compounds containing the ‐N(CH3)2, group. Part VI: Complexes of hexamethylphosphoramide and nonamethylimidodiphosphoramide with metal perchlorates

Abstract: A number of new perchlorate complexes of the ligands hexamethylphosphoramide and nonamethylimidodiphosphoramide is reported The compounds are characterized and identified by chemical analysis and physical measurements A number of complexes which were reported earlier by other workers, were reprepared and their properties were studied with the aid of X-ray powder measurements, infrared and ligand-field spectra In some cases this leads to quite different conclusions, which are supported by the results found for the new complexes The raman spectrum of nonamethylimidodiphosphoramide is reported for the first time and it is shown that this facilitates the assignment of absorption bands in the complexes It is pointed out that planarity of the six-membered ring , which is in some way suggested by infrared and raman measurements might explain the unusual stability of complexes with the ligand nonamethylimidodiphosphoramide

A method for determination of tulipalin A and B concentrations in crude extracts of tulip tissues

Abstract: A method for determining the concentration of the fungitoxic lactones tulipalin A and B in crude extracts of various parts of the tulip is described. After a simple fractionation of the extracts on Dowex 50 W, the amounts of these compounds can be measured by UV spectrophotometry.

Model studies for enzyme inhibition. Part V: Reactions of organophosphorus compounds with α-cyclodextrin. A quantitative approach of model activity and stereospecificity†

Abstract: The bimolecular rate constants for reaction of the enantiomers of isopropyl methylphosphonofluoridate, isopropyl p-nitrophenyl methylphosphonate and isopropyl S-2-dimethylaminoethyl methylphosphonothioate with α-cyclodextrin have been calculated from the dissociation constants (Kdiss) of the prereaction 1:1 inclusion complexes and the maximal rate constants (k2max) for the ensuing nucleophilic reactions. These data are compared with the corresponding rate constants for the inhibition of acetylcholinesterase. It is concluded that the stereospecificity exhibited by α-cyclodextrin in its reaction with enantiomeric organophosphorus compounds is reflected mainly in the nucleophilic reaction.

The nature of the s‐s bonds in different compounds II The crystal and molecular structure of diphenyl disulfone

Abstract: The crystal structure of diphenyl disulfone has been determined by X-ray diffraction at room temperature. Observed (average) values for the bonds involving a sulfur atom are: S S 2.193(1), SO 1.428(1), SC 1.753(1) A. In parentheses the standard deviations for the individual bonds are given.

Heterocylic synthesis via 1‐amino‐3‐oxo‐1‐cyclohexene

Abstract: 2,5-Dioxo-1,2,5,6,7,8-hexahydroquinoline 2 is formed upon condensation of methyl propiolate with ketone 1 in DMF as solvent. On the other hand, reaction 1 with propargylic acid led to 1,8-dioxo-perhydroacridine 4b as the sole isolable product.

Réactions D'Hétérocycles Oxygénés avec les Trialcoylsilyl-, -Germyl- et -Stannyl-Phosphines: II. Cas des lactones et des anhydrides d'acide

Abstract: The trialkyl-silyl-, -germyl- and -stannyl-phosphines R3MPEt2 react with β-propiolactone via the cleavage of the alkyl-oxygen bond of the lactone, leading to the trialkylmetal β-diethylphosphinopropionates R3MOCOCH2CH2PEt2 (M = Si, Ge, Sn). These reactions are accompanied by a strong polymerization of the β-propiolactone. The germyl- and silyl-phosphines cleave γ-butyrolactone at a rather high temperature and in the presence of catalyst (ZnCl2). Only the acyl-oxygen scission is observed in this case, with formation of the phosphorated ketoalkoxymetal derivatives R3MO(CH2)3COPEt2. Under the same conditions, the stannylphosphines decompose before reacting. In the case of the hydrosilylphosphines R2(H)SiPEt2, the ketoalkoxymetal derivative cyclises by intramolecular addition SiH/C=O with formation of 2-sila-1,3-dioxepane with a phosphorated substituent: The same acyl-oxygen cleavage is observed in the action of the metal-IVb phosphines on succinic anhydride to lead to the ketoesters R3MOCO (CH2)2COPEt2 (M = Si, Ge, Sn). The action of the hydro-germyl- or -silyl-phosphines R2(H)MPEt2 leads, in a first phase, to the corresponding γ-ketoesters R2(H)MOCOCH2CH2COPEt2 which cyclise via intramolecular addition with formation of cyclic germa- or sila-alkoxy esters.

Liquid‐phase CO‐oxidation of aldehydes and olefins radical versus non‐radical epoxidation

Abstract: In co-oxidations of aldehydes and olefins with molecular oxygen in the liquid phase, epoxides are formed via two different routes: (1) by reaction of intermediate acylperoxy radicals with the olefin, and (2) by a non-radical reaction of intermediate peracid with the olefin. For the systems benzaldehyde cis-1, 2-D2-1-octene and benzaldehyde cis- and trans-2-octene the ratio of radical to non-radical epoxidation has been calculated with the aid of the kinetic relationships derived for this type of reaction and has been determined experimentally from the stereo selectivity of the expoxidation and from the production of carbon dioxide. The results show that the ratio of radical to non-radical epoxidation increases with increasing reactivity of the olefin as well with increasing olefin/aldehyde ratio.

Kinetics of the cis‐trans isomerization of the diaquotetra‐amminecobalt(III) cation and conjugate bases

Abstract: A study is reported on the cis-trans isomerization rates and equilibria of the ions Co(NH3)4(H2O)23+, Co(NH3)4(OH)(H2O)2+ and Co(NH3)4(OH)2+ in acidic and ammoniacal solutions. The relative reaction rates follow the pattern shown by the analogous ethylenediamine complexes, whereas the absolute rates for the ammine complexes studied are a 100 times larger.

Investigations on organogermanium compounds. XIII: Synthesis of linear peralkylpolygermanes. Mechanism of the reaction of trialkylgermyl alkali metal compounds with trialkylhalogenogermanes†‡

Abstract: A full report is given of our investigations into the synthesis of a series of linear peralkylpolygermanes, both by reacting organohalogenogermanes with alkali metals and by coupling of organohalogenogermanes with trialkylgermyl alkali metal compounds2–4. The latter type of reaction always gives in addition to the asymmetric compound R3GeGeR3′, varying amounts of the symmetrical products R6Ge2 and R6′Ge2. Evidence is presented that these side-products are formed by a nucleophilic cleavage of the GeGe bond of the primary asymmetrical coupling products, rather than by a halogen-metal exchange reaction.

Structure and physical properties of aluminium alkoxides. Part IV: Vapour pressures of aluminium isopropoxide

Abstract: The vapour pressure of aluminium isopropoxide is measured statically at temperatures ranging from 80° to 126°. In the lower part of this range the compound is more volatile than is indicated by previous data. For the latent heat of vaporization a value of 11.5 ± 1.5 kcal/mole is calculated. This low value points to just small shifts in degree of association upon vaporization.

Reaction of methylpyrazinecarbonitriles and 2-methylquinoxaline with phosphorus oxychloride and organomagnesium compounds

Abstract: In the preparation of methyl methylpyrazinyl ketones by the sequence methyl-pyrazinecarboxylic ester, amide, nitrile, to ketone, methylpyrazinecarbonitriles were found to react with phosphorus oxychloride forming tricyclic compounds related to “2-methylquinoxaline orange”. 2-Methylpyrazine-6-carbonitrile with methylmagnesium iodide underwent addition at one of the ring CN bonds. 2-Methylquinoxaline reacted similarly with phosphorus oxychloride, and organomagnesium compounds. The methyl methylpyrazinyl ketone described in literature as the 2,6-isomer was shown to be the 2,5-isomer.

Photochemical cycloaddition of 9,10‐phenanthroquinone to allenes III: A kinetic study

Abstract: Phenanthroquinone was added photochemically to phenyl-, phenoxy-, t-butyl-, t-butoxy-, cyano- and bromo-allene yielding dihydrodioxin derivatives. Quantum yields and rate constants of the reaction of phenanthroquinone with several substituted allenes were determined. For comparison also quantum yields were measured of the reaction of phenanthroquinone with some corresponding alkenes. The influence of substituents on the reaction rates could satisfactorily be correlated with a ρσ-γER relationship of Yamamotu and Otsu.

Activation and transfer of oxygen VII: Synthesis and spontaneous oxidation of some 1, 8-blocked tetrahydropteridines†

Abstract: Some tetrahydropteridines carrying methyl substituents at the N(1)-, N(3)-and N(8)-positions were synthesized and subjected to autoxidation (V and XIII). A spontaneous oxidative contraction of the pyrimidine ring occurred in aqueous solution (XIII + O2 XXI). This result was in agreement with a theory which has already been put forward. 5-Acetyl-tetrahydropteridines were required for synthetic purposes. They could not generally be prepared by reduction of pteridines with zinc/acetic acid/acetic anhydride. A contraction of the pyrazine ring occurred in the attempted reductive acetylation of 1, 3, 6, 7-tetramethylpteri-2, 4-dione (IX). The product was identified as 1, 3, 8-trimethyl-2, 6-dioxopurine (XIV = 8-methyl-theophylline). Starting from 1, 3-dimethylpteri-2, 4-dione the same procedure led to a mixture of two dimeric acetyl-tetrahydropteridine derivatives.

The reduction of alkylnaphthalenes with lithium in liquid ammonia

Abstract: The reduction of naphthalene and alkylnaphthalenes with lithium in liquid ammonia has been studied. With excess of alkali metal and in the absence of a proton donor the reaction yields tetralins. The reduction of 1, 4-dideuteronaphthalene shows that the first proton addition at an α-position is irreversible and that the amide-catalyzed isomerization of the initially formed 1, 4- into the 1, 2-dihydronaphthalene is mainly a one step process. This isomerization is the rate-determining step in the reduction to tetralin. Reduction of 1-alkyl- and 1, 4-dialkyl-naphthalenes occurs mainly in the unsubstituted ring. With 2-alkyl-naphthalenes the selectivity of ring reduction depends on the alkyl group; in 2-methylnaphthalene the substituted ring is about twice as reactive as the unsubstituted ring whereas the reverse is true for 2-t-butylnaphthalene.

Studies of inter‐ and intra‐molecular donor‐acceptor interactions ‐ X: Intramolecular Charge transfer interaction in substituted N‐aralkyl‐phthalimides and ‐1,8‐naphthalimides

Abstract: Compounds D-(CH2)n-A (n = 1-5) are studied, in which D = an aromatic group with low ionization potential (e.g. an electron donor) and A is mainly the N-3,6-dinitro-1,8-naphthalimide group. Especially for n = 1 and n = 3, interaction between D and A leads to the observation of discrete intramolecular C(harge) T(ransfer) transitions in the electronic absorption spectra. For n = 1 this is explained by “homoconjugative” interaction, while for n = 3 the molecules probably adopt a folded conformation, a suggestion which is suppported by NMR data. For n = 2 close approach of D and A seems to be sterically excluded, while for n > 3 the interaction between D and A rapidly diminishes. For the compound with D = 9-anthryl and n = 3 steric interaction between the peri-hydrogens of the anthryl group and the trimethylene chain seems to inhibit the molecule from adopting a folded conformation. For the compounds with D = p-dimethylaminophenyl and n = 3 or 4 a double intramolecular CT transition is observed; a tentative explanation for this phenomenon is given.

Decyanation of cyanomethyl derivatives of aza‐aromatic compounds

Abstract: 2- and 4-Cyanomethylpyridine, 1-methyl- and 1-benzyl-2-cyanomethylimidazole and 3-cyanomethyl-1,2,4-triazole lose the cyano group on reaction with aqueous hydrazine at about 200°, yielding α- and γ-picoline, 1,2-dimethyl- and 1-benzyl-2-methylimidazole and 3-methyl-1,2,4-triazole, respectively. A mechanism is discussed.

Properties of cyclodextrins. Part VII: Gaschromatographic determination of the solubility of saturated hexane and 2,3‐dimethylbutane vapours in aqueous solutions of cyclodextrin derivatives

Abstract: Specific interaction of aqueous solutions of cyclodextrin derivatives has been investigated with respect to the isomers hexane and 2,3-dimethylbutane. Saturated vapour of hexane or 2,3-dimethylbutane is equilibrated with aqueous solutions of different concentrations of cyclodextrin derivatives at 1, 10, 20, 30 and 40°. The solubilities of the hydrocarbons in these solutions and in water are measured gaschromatographically. It appears that linear interaction isotherms are formed, from which the degree of occupation of the cyclodextrin voids can be calculated, assuming for the present a 1 : 1 composition of the inclusion complex. The complex association constant has been calculated for the equilibrium: saturated vapour + cyclodextrin derivative ⇆ inclusion complex. Plots of the natural logarithms of the association constants vs 1/T show linear relationships. The standard molar values of the free enthalpy, enthalpy and entropy pertaining to the above-mentioned equilibrium have been calculated.

The molecular and crystal structure of dipotassium mesitylene‐disulfonate dihydrate

Abstract: Dipotassium mesitylenedisulfonate dihydrate crystallizes in monoclinic needles, space group P21/c, cell constants a = 7.341, b = 12.330, c = 15.934 A, β = 94.60°, Z = 4. The overcrowding of substituents in the mesitylenedisulfonic group does not affect the bond lengths, but changes the bond angles, planarity and geometry of the molecule significantly.

Constantes ρ de Hammett dans les Reactions de Formation D'Oximes et de Combinaisons Bisulfitiques

Abstract: The Hammett reaction constant ρ has been measured for the addition reactions of NH2OH and SO−−3 ion to carbonyl compounds; the slopes of the best straigt lines of the log k, σ correlation fonctions are respectively: 0.32 and 1.12. These values are used to. draw conclusions concerning the structure of the transition state and its position along the reaction coordinate; they are consistent with a ‘reactant like’ transition state.