Showing papers in "Recueil des Travaux Chimiques des Pays-Bas in 1960"

On the impedance of galvanic cells: I. Theory

Abstract: Impedances of galvanic cells are treated as complex quantities and graphical methods for the determination of reaction rate constants of the redox reactions, double layer capacities, ohmic resistances and diffusion constants are proposed.

The effect of ultraviolet light on some components of the nucleic acids. VI The origin of the U.V. sensitivity of deoxyribonucleic acid

Abstract: The rapid decrease in extinction of deoxyribonucleic acid in the first moments of irradiation with U.V. light (2537 A) is due to the conversion of the pyrimidines into low-absorbing substances. Thymine in this natural polymer reacts according to the so-called “first irreversible reaction” shown by the free bases in solution. This could be demonstrated by means of a peculiar property of the irradiation product of thymine. Cytosine is supposed to react in the same way. The importance of this finding with respect to the lethal action of U.V. light on micro-organisms is discussed.

Physical properties of organic thiones. Part I. Electronic absorption spectra of nitrogen-containing thione compounds

Abstract: The electronic absorption spectra of some thioamides, dithiocarbamic esters, thioureas and one thioncarbamic ester are recorded in a hydrocarbon, diethyl ether, ethanol and concentrated sulphuric acid as solvents. The bands are classified according to their intensities and solvent effects. It is shown that the assignment of Koch must be reversed. The spectra of substituted thioureas are discussed in relation to their spatial structures.

On the impedance of galvanic cells: II. Experimental verification

Abstract: It is shown by experiment that both types of frequency dependency of the cell impedance, treated in Part I, occur. From the results the diffusion constant of the Hg++2 ion in 1M HClO4 and the reaction rate constant of the zinc amalgam electrode in 1M NaClO4 + 10−3M HClO4 base electrolyte are calculated. In addition the value of the double layer capacity of the zinc amalgam electrode is reported.

Physical properties of organic thiones: Part III. The evaluation of transition energies, resonance energies and charge diagrams of organic thiones and dithioates

Abstract: An empirical LCAO MO method, in which self-consistency was introduced, was applied to molecules of the general structure ABCS and ACS2−, in which A and B are saturated radicals bonded to the thione or dithioate group by carbon, sulphur, oxygen or nitrogen. The transition energies for n π* and π π* transitions, the resonance energies and the charge diagrams are evaluated. The calculated transition energies proved to be related to the measured absorption frequencies for both transitions. A discrepancy is encountered between the experimental and theoretical assignment of the π π* transition for the nitrogen-containing thiones.

Physical properties of organic thiones. Part II. Electronic absorption spectra of compounds containing the thiocarbonyl group

Abstract: Electronic absorption spectra of compounds containing a thiocarbonyl group bound to carbon, sulphur or oxygen are reported. The spectra were taken, whenever possible, in cyclohexane, ethanol and concentrated sulphuric acid. The bands are compared with those of nitrogen-containing thiones and an empirical assignment of the different types of bands is given.

Chemistry of acetylenic ethers XLVI: Addition of thiols to acetylenic ethers

Abstract: The free-radical addition of ethanethiol to ethoxyethyne produces much cis and a little trans 1-ethoxy-2-(ethylthio)ethene, whereas the nucleophilic addition of sodium ethanethiolate yields 1-ethoxy-1-(ethylthio)ethene. The same applies to additions of other thiols.

Mechanism of reactions of unsaturated ethers and thioethers. I: Add catalyzed addition of water to acetylenic thioethers

Abstract: The acid catalyzed addition of water to ethylthioethyne has been studied in aqueous solution. The reaction is general acid catalyzed and it is faster in H2O than in D2O. Substitution of a tertiary butyl group for the ethyl group results in a rate enhancement. The entropies of activation ΔS≠ for the hydration of ethylthioethyne and tertiary butylthioethyne are - 6.1 and - 0.6 cal. mole−1, deg.−1, respectively. These facts strongly suggest that protonation of the alkylthioethyne is the rate controlling step of the reaction.

Thermal quantities of cycloparaffins: Part IV. Heats of combustion of cycloparaffins with 10-17 C atoms†‡§

Abstract: The heats of combustion at 25° of purified samples of the cycloparaffins having from 10 to 17 C atoms, have been measured. A brief description is given of the preparation and purification of the samples. The enthalpies - ΔHR, given in the table below refer to the reactions: at 25° and 1 atm. A discussion will be given in a later paper.

Preparation of quinazoline derivatives through ring closure of aromatic ortho-cyano-acylamino compounds in alkaline alcoholic or phenolic medium II†

Abstract: Some new quinazoline derivatives were prepared by boiling the appropriate ortho-cyano-acylaminobenzene in alkaline alcoholic medium. Proofs of the constitution of the quinazoline derivatives are given.

Square wave electrolysis II: The cyclic current‐step method

Abstract: A new method, designated the cyclic current-step method, for the evaluation of kinetic parameters of electrochemical processes (especially the exchange current j0) is introduced in addition to the well-known (single) current-step method. Its essential basis is that a square wave current is forced through a polarisable electrode and the voltage response of the electrode is measured. It is shown mathematically that the voltage response approaches a constant pattern when “coulomb-symmetry” is present and a gradually changing pattern is observed when a departure from coulomb-symmetry occurs. Even when the pattern is continuously changing due to the presence of coulomb-asymmetry the evaluation of j0 may be easily achieved. By means of the cyclic current-step method it is easily visualised whether or not the influence of the double layer capacity is negligible. Moreover, the method provides a ready means for the elimination of the ohmic part of the voltage response of the electrolytic cell.

Square wave electrolysis. I. The cyclic potential‐step method

Abstract: Drawbacks of the well-known potential-step method are briefly mentioned. A new method called the cyclic potential-step method is introduced, the essential of which is that a square wave voltage is applied to a polarisable electrode. It is shown mathematically that the current response approaches rapidly to a constant pattern. The derivations presented are free from restrictions concerning the reversibility of the system and the magnitude of the amplitude of the square wave. It is shown that the cyclic potential-step method offers easy means for the determination of the transfer-coefficient (α) and the standard exchange current density (j00).

Mechanism of reactions of unsaturated ethers and thioethers II: Dipole moment and charge shift in acetylenic ethers†

Abstract: Electric dipole moments of the following compounds have been measured in benzene solution: C2H5OC2H5, H2CCHOC2H5, HC ≡ COC2H5, H3CC ≡ COC2H5, HC ≡ COCH3 and H3CC ≡ COCH3. The charge shift, caused by resonance, in HC ≡ COC2H5 and HC ≡ COCH3 amounts to approximately 0.11 e.

Alkyl‐substituted benzaldehydes

Abstract: The ortho-, meta- and para-isomers of methyl-, ethyl-, isopropyl- and tertiary butylbenzaldehyde have been synthesized for the purpose of an olfactory study1 . The aldehydes were isolated and purified via the semicarbazones. The ultra-violet absorption spectra of the aldehydes as well as those of the semicarbazones were determined. Particular attention was paid to ortho-alkylbenzaldehydes as to whether there is any steric effect of mesomerism.

Ester interchange equilibria from dimethyl terephthalate and ethylene glycol

Abstract: Ester interchange equilibrium products prepared from dimethyl terephthalate and ethylene glycol, in the presence of zinc acetate as a catalyst, have been investigated at 180 and 195°. For the analysis of these products quantitative volumetric methods for the determination of free methanol and of free ethylene glycol have been developed. In addition, a method for the fractional vacuum distillation and sublimation of methanol, ethylene glycol, dimethyl terephthalate, and β-hydroxyethyl methyl terephthalate has been worked out. The analytical results are evaluated in terms of equilibrium constants for the various reversible reactions pertaining to the present system. All equilibrium constants are found to depend only slightly on temperature and composition. The small values of the equilibrium constants related to the removal of methyl ester groups are in line with the practical difficulty of achieving complete glycolysis of dimethyl terephthalate before polycondensation to polyethylene terephthalate starts. The most important result is the fact that the “molecular” equilibrium constant KI of the first step of the glycolysis of dimethyl terephthalate equals the corresponding overall equilibrium constant Ke in terms of functional groups after correction for the functionality of reactants and products. Prom this fact it is concluded that the “molecular” equilibrium constants KI and KII for the first and second step of the glycolysis are equal.

Tautomerism of hydroxypyridines (II). Bromination of 2,4‐dihydroxypyridine and its ethyl derivatives

Abstract: 2,4-Dihydroxypyridine, 2-ethoxy-4-hydroxypyridine, 4-ethoxy-2-hydroxypyridine and 2,4-diethoxypyridine were brominated in pyridine as solvent. It appeared that bromine enters the 3-position during the bromination of the three first mentioned substances whereas from 2,4-diethoxypyridine the 5-bromo derivative is formed. Ultraviolet absorption spectra of substrates and reaction products in 50% aqueous ethanolic solution were measured. Comparison of these spectra with the known spectra of the mono- and dimethoxy derivatives of 2,4-dihydroxypyridine enabled the tautomeric structures of the substances to be investigated. The course of the brominations is connected with the structure of the substrates.

Studies in IVth group organometallic chemistry. VI: Preparation and polymerization of IVth group organometallic derivatives of styrene and α‐methylstyrene

Abstract: : The preparation of a series of IVth group organometallic vinyl monomers derived from styrene and a-methylstyrene, respectively, is described. Thermal or radical-initiated polymerization of the styrene derivatives yielded transparent, solid organometal-substituted polystyrenes. The monomers of the general structure p-(CH3)3M(IV)-C6H4-CH-CH2 display appreciably different rates of radical-initiated polymerization, i.e. in the order Pb > Si > C > Ge > Sn. (Author)

Note on the preparation of 3‐hydroxy‐5‐hydroxymethyl‐2,4‐dimethyl‐pyridine: (4‐Desoxyadermine)

Abstract: The intermediate steps in the synthesis of 4-desoxy-adermine described some time ago have been improved upon, particularly the conversion of the last intermediate 3-amino-2,4-dimethyl-5-methyl-amino-pyridine (VII) to desoxyadermine. As a result of these improvements, desoxyadermine can now be synthesized in an overall yield of 15%, based on the starting materials acetyl acetone and cyanoacetamide.

Synthesis of a tyrosine “homologue” of oxytocin

Abstract: A synthesis is described of the “protected” decapeptide N-benzyloxycarbonyl-S-benzyl-L-cysteinyl-L-tyrosyl-L-tyrosyl-L-isoleucyl-L-glutaminyl-L-asparaginyl-S-benzyl-L-cysteinyl-L-prolyl-L-leucylglycineamide (V). Removal of the blocking groups from V followed by oxidation yielded biologically active preparations believed to contain a “homologue” of oxytocin with two consecutive molecules of tyrosine instead of one (VI). Oxytocin-inhibiting activities of VI have been described by other investigators.

Phosphatidic acids and derivatives: XI. Infra‐red spectra of glycerol‐α‐kephalins and glycolkephalins

Abstract: In the present paper we are publishing the infra-red spectra of glycerol-α-kephalins and glycolkephalins synthesized in our laboratory. These spectra are discussed in relation with spectra of glycerol-α-kephalins already available in the literature.

The structure of the compound diphosphotrioxytetrachloride, P2O3Cl4

Abstract: The frequencies of and the polarization of most of the Raman lines of liquid P2O3Cl4 have been determined. The molecule contains an oxygen bridge connecting two groups. From the polarization measurements it is deduced that at least one symmetry element is still present in the molecule.

Chemistry of acetylenic ethers XLVII: Preparation of α-ketols from ethoxyethynylcarbinols

Abstract: A method is described for converting ethoxyethynylcarbinols I into α-ketols V, via the intermediate products II to IV inclusive. The synthesis occurs stereospecifically and, starting from the ethoxy-ethynylcarbinol VII, derived from 3β-acetoxyandrost-5-en-17-one VI, affords almost exclusively 3β,21-dihydroxypregn-5-en-20-one XI in about 50% yield.

Investigations on herbicides III: 2,4‐Disubstituted 6‐chloro‐1,3,5‐triazines

Abstract: In view of their herbicidal properties a number of similarly or differently 2,4-substituted 6-chloro-1,3,5-triazines was synthesized. Their herbicidal properties are briefly discussed.

N.M.R. spectra of some derivatives of nitrocyclopropane

Abstract: As part of the investigation of the structure of “trismethylene-trinitrobenzene” VIa, N.M.R. spectra are recorded of a number of its degradation products, viz. the dicarboxylic acid Ia, anhydride IIa, trans-nitrocyclopropane carboxylic acid III, the corresponding cis isomer IV and the lactone Va. The spectra are in accordance with the presence of cyclopropyl groups in all these compounds; alternative olefinic structures can definitely be excluded. Furthermore some information is obtained from the spectrum of “trismethylene-trinitrobenzene”, supporting structure VIa and excluding VIb. The protons of the cyclopropyl rings of compounds Ia and IIa are easily recognised as belonging to the AB2 and ABX classes, respectively. For these two compounds the chemical shift and the spin-spin coupling constant have been calculated.

Study of the reactions between titanium tetrachloride and ethylaluminium compounds in hydrocarbon solution: II. Gaseous reaction products

Abstract: Gaseous reaction products from the systems AlEt3/TiCl4, AlEt2Cl/TiCl4 and AlEtCl2/TiCl4 in isooctane solution at 80°C have been studied A set of reactions explaining the formation of the observed products H2, C2H6, C2H5Cl, n-C4H10 and n-C6H14 is given It is possible to account nearly quantitatively for the conversion of the ethyl groups and for the extent of reduction of TiCl4 It appeared that the formation of ethane is partly due to dis-proportionation of ethyl groups, and partly to ethyl groups abstracting hydrogen from the isooctane In the system AlMe3/TiCl4 the methyl groups quantitatively react in the latter way to form CH4 The isooctane to a small extent decomposes into isobutane and isobutene or into isopentane and propene It is supposed that the brown precipitates formed in the reduction of TiCl4 act as catalysts for this decomposition

A study of the ziegler‐type combinations TiCl4‐n‐C5H11Na and TiCl4‐(C2H5)2AlBr

Abstract: The reaction between catalyst components has been studied and polymerization experiments carried out on ethylene using the systems pentyl-sodium – TiCl4 (I) and diethylaluminium bromide – TiCl4 (II). Results of reduction of TiCl4 can be interpreted on the basis of the following equations: AmNa + TiCl4 TiCl3 + NaCl + Am•, in the case of I, Et2AlBr + TiCl4 TiX3 + EtAlX3 + Et• and EtAlX2 + TiCl4 TiX3 + + AlX3 + Et• (X = Cl, Br), in the case of II. The occurrence of the second reaction in II was confirmed by analyses of the precipitates formed in the reaction and by reacting TiCl4 with EtAlBr2. The reducing power of the organometallic compounds examined decreases in the range: AmNa > Et2AlBr > EtAlBr2. Polymerization results with system I showed that active catalysts are obtained only with AmNa/TiCl4 mole ratios > unity. The polymer yield appeared to increase with increasing catalyst ratio. This may reasonably be explained by postulating the existence of an AmNa-TiCl3 complex as the actual catalytic species. In this range of catalyst ratios, the intrinsic viscosities of the polyethylenes remain approximately constant. In the case of system II, polymerization results could also be interpreted by assuming the existence of one complex or a mixture of a number of complexes as the catalyst. With Et2AlBr/TiCl4 mole ratios > ∼ 2, a complex between Et2AlBr and TiCl3 (Et2AlX-TiX3) is postulated. With catalyst ratios in the vicinity of unity and lower, ambiguous results were obtained due to the occurrence of reactions between the catalyst components during polymerization.

The microchemistry of the platinum metals. Separation and determination of micro amounts of rhutenium, rhodium and palladium

Abstract: A method is outlined for the separation and determination of small amounts of ruthenium, rhodium and palladium individually as well as in combinations of two or even all three elements mentioned. It is based principally upon reactions of these elements with 8-hydroxyquinoline. Determinations are carried out spectrophotometrically on the metal oxinate extract in chloroform. The procedure gives reproducible results and provides a. rapid method for the determination of each of the three elements even in their mixtures.

Rapid determination of vapour‐liquid equilibria

Abstract: An apparatus for the determination of vapour-liquid equilibria at constant pressures within the range of 760 to 10 mm Hg is described The apparatus can produce eight pairs of samples of coexisting vapour and liquid, evenly distributed over the concentration range in one run within two hours As a proof of its operation the results obtained with six binary systems are recorded The systems investigated are: Carbon tetrachloride-benzene Carbon tetrachloride-toluene Benzene-dichloroethane n-heptane-methylcyclohexane methylcyclohexane-toluene n-decane-trans-decahydronapththalene The results obtained agree with a thermodynamic criterion which is discussed separately

A synthesis of 1‐hydroxy‐8‐methoxyanthraquinone‐3‐carboxylic acid

Abstract: The structure of 1‐hydroxy‐8‐methoxyanthraquinone‐3‐carboxylic acid, previously obtained by the action of dimethyl sulphate on the sodium salt of synthesized rhein monoglucoside, has now been confirmed by synthesis.

Synthesis of a tyrosine “homologue” of oxypressin

Abstract: The synthesis is described of the protected linear decapeptide: N-benzyloxycarbonyl-S-benzyl-L-cysteinyl-L-tyrosyl-L-tyrosyl-L-phenylalanyl-L-glutaminyl-L-asparaginyl-S-benzyl-L-cysteinyl-L-prolyl-L-leucylglycineamide (III, Fig. 2). Removal of the blocking groups from III, followed by oxidation, yielded a preparation assumed to contain a “homologue” of oxypressin with two consecutive molecules of tyrosine instead of one (Fig. 1, n = 2).