Additional CH2 Research Articles

Kinetics of oxidation of 3-aminopropan-1-ol and related compounds by silver(III) species

The oxidation of 3-aminopropan-1-ol (3-AP) and certain diamines by diperiodatoargentate(III) (DPA) has been studied by stopped-flow spectrophotometry at pH 8.0. The kinetics of the reaction of 3-AP consist of three steps—an induction period, then a fast decay, which is followed by a slower decay. The initial step involves the axial binding of the substrate to the silver(III) species; this rearranges during the induction period (0.2 s) and takes up another ligand in the following step with a second-order rate constant of 4 × 103 dm3 mol−1 s−1 to yield [AgIII(H2IO6)(3-AP)2]. The silver(III) centre in this complex is reduced by 3-AP in the rate-determining step with a rate constant of 0.50 × 102 dm3 mol−1 s−1. Both of these processes show inverse dependence on [IO4−] and [OH−]. The kinetics of the oxidation of diamines by silver(III) follow a different kinetic behaviour. The rates of their complexation and oxidation follow the order 1,2-diaminoethane > 1,3-diaminopropane > 1,4-diaminobutane. Separation of the two functional groups by an additional CH2 in the studied substrates reduces the rates of both the steps. In case of the diamines, the formation of a cyclic complex involving silver(III) and the substrate prior to its oxidation is suggested. The mechanisms of these reactions are being analysed.

Syntheses and Comparative Base Hydrolysis Reactions of Chlorocobalt(III) Complexes of Pendant-Arm Macrocyclic Polyamines and Polyamino Acids

Chlorocobalt(III) complexes of the pendant-arm macrocycles 1,4,8,12-tetraazacyclopentadecane-10-carboxylate (2) and 1,5,9,13-tetraazabicyclo[11.2.2]heptadecane-7-carboxylate (4) have been prepared to complement the known complexes of 10-methyl-1,4,8,12-tetraazacyclopentadecan-10-amine (1) and 7-methyl-1,5,9,13-tetraazabicyclo[11.2.2]heptadecan-7-amine (3). The pairs (1),(3) and (2),(4) differ in replacement of pendant amine and methyl groups in the former pair by a pendant carboxylate group and hydrogen in the latter pair. The macromonocyclic ligands (1) and (2) form cis-chlorocobalt(III) complexes whereas the macrobicyclic ligands (3) and (4) (which contain an additional –CH2–CH2– ‘strap’ linking two amines) form trans-chlorocobalt(III) complexes, defined in terms of location of the pendant donor and the chloride donor. Chloride base hydrolysis kinetics varies with ligand {cis-[Co(1)Cl]2+, kOH 6700 dm3 mol-1 s-1 ; cis-[Co(2)Cl] +, kOH 1800 dm3 mol-1 s-1;trans-[Co(3)Cl]2+, kOH 3450 dm3 mol-1 s-1; trans-[Co(4)Cl]+, kOH 2250 dm3 mol-1 s-1 at 25°C}. Variations in rate constant are tied mainly to variations in activation enthalpy. Chloride hydrolyses occur with retention of configuration, but slow following isomerization can lead to products such as trans-[Co(2)(OH2)] (ClO4)2.2H2O, which crystallizes in the monoclinic space group P21/c, a 9·581(2), b 16·214(2), c 14·350(2) Å and β 94·66(1)°. The pendant carboxylate group and two adjacent secondary amines necessarily occupy an octahedral face, with the water molecule bound trans to the pendant carboxylate. The four Co–N distances range from 1·981(2) to 2·22(3) Å, and along with carboxylate Co–O (1·882(3) Å) and water Co-O (1·934(2) Å) distances are similar to usual distances in cobalt(III) complexes.

Polycarboxylic acids containing acetal functions: calcium sequestering compounds based on oxidized carbohydrates

AbstractA number of polycarboxylic acids containing acetal functions have been prepared by a two‐step oxidation of carbohydrates. Their calcium sequestering behavior is compared with that of a series of model polycarboxylic acids. It is found that calcium sequestration by oxidized carbohydrates is less than that by corresponding ether polycarboxylates, since (a) acetal oxygens have a lower coordinating power than ether oxygens, and (b) there is extra steric repulsion upon calcium complexation by both the additional CH2 OH groups and the unfavorable natural configuration of the oxidized carbohydrates investigated. Some of the oxidized carbohydrates show greater calcium sequestering capacities than corresponds to the stability constant. This is probably caused by crystal growth inhibition or precipitation‐inhibition phenomena. Two model compounds illustrate that the acetal moiety is sufficiently stable under washing conditions, whilst it hydrolyses under acidic waste water conditions into small (hydr)oxycarboxylates.

Purification and properties of the P2 primary alkylsulphohydrolase of the detergent-degrading bacterium pseudomonas C12B.

The P2 primary alkylsulphohydrolase of the soil bacterium Pseudomonas C12B was purified to homogeneity (200-250-fold) by column chromatography on DEAE-cellulose, Sephadex G-100 and butyl-agarose. The intact protein is a dimer with a mol. wt. of 160 000. Activity towards primary alkyl sulphate esters was maximal at pH 8.3, varied little in the range pH 7.8-8.7, but decreased sharply at higher pH. For a homologous series of primary alkyl sulphate substrates (C6-C12), logKm decreased linearly with increasing chain length, corresponding to a contribution to the free energy of association between enzyme and substrate of -2.5kJ/mol for each additional CH2 group in the alkyl chain. logKi for the competitive inhibition by secondary alkyl 2-sulphate esters followed a similar pattern (-2.4kJ/mol for each additional CH2 group) except that only n-1 carbon atoms effectively participate in hydrophobic bonding, implying that the C-1 methyl group is not involved. logKi values for inhibition primary alkanesulphonates also depended linearly on chain length but with a diminished gradient, indicating a free-energy increment of -1.2kJ/mol per additional CH2 group. The collective results showed the presence of a hydrophobic site on the enzyme capable of accomodating an alkyl chain of considerable length. Cationic structures (in the form of arginine, lysine or histidine), whose presence might be expected for binding the anionic sulphate group, were not detectable at the active site.

The surface activity of the lower homologues of n-alkylammonium chlorides in aqueous solutions. Effect of hydrophobic hydration

The surface tensions of aqueous solutions ofn-alkylammonium chlorides (methyl to hexyl) have been measured at 25 °C. With methylammonium chloride the surface tension increased with concentration, whereas with ethylammonium chloride and higher homologues, the surface tension decreased with concentration. The results suggest that this transition is attributed to the effect of hydrophobic hydration. For propylammonium chloride and higher homologues, the relation between the surface tension lowering da and the concentrationC in the range of 0–10 dyne/cm, can be expressed by the equation;Δσ = A√C + BC, whereA andB are constants. The surface tension coefficientB has been found to increase approximately twofold for each additional CH2 group of alkyl chain.

Carrier-amino acid stoichiometry in amino acid transport in ehrlich ascites cells

1.1.The initial flux of l-tryptophan in “exchange diffusion” and in “competition” experiments with other amino acids is significantly increased by certain of the amino acids.2.2.For the straight-chain amino acids with aliphatic side chains, there is a progressive, almost constant increase in the stimulatory effect obtained in these experiments for each additional CH2 group in the side chain.3.3.In the competition experiments, branching the chain, decreases the stimulation of initial flux.4.4.A model of the transport system in which the ratio of amino acid to carrier is I:I can predict the stimulation in the exchange-diffusion experiments. An Amino acid to carrier ratio of 2:1 must be assumed to also predict the stimulation observed in competition experiments.

Raman Spectra of Some Disubstituted Diacetylenes

Raman frequencies and relative intensities are reported for dimethyldiacetylene, diethyldiacetylene, dipropyldiacetylene, dibutyldiacetylene, and diamyldiacetylene. Depolarization factors also were obtained except for diethyldiacetylene. The relative intensities and depolarization factors were obtained with the use of a Gaertner microdensitometer. A tentative assignment was made of all the observed Raman frequencies of dimethyldiacetylene, assuming that it has the symmetry D′3h. Using the chain and methyl group frequencies thus established for dimethyldiacetylene, a comparison was made with the other spectra in order to determine how these frequencies are affected by introducing additional CH2 groups into the dimethyldiacetylene molecule. A comparison was made of the Raman spectra of the disubstituted diacetylenes with those of the corresponding acetylenes. For dimethyldiacetylene, three cases of Fermi resonance occurred, but there were also two cases where only a single line was observed, in spite of the fact that the frequency and symmetry conditions for resonance were satisfied. The carbon-carbon triple-bond frequency, which appears at 2183 cm−1 for diacetylene, increases to 2264 for dimethyldiacetylene, then drops to 2251–2257 for the other four compounds.