Acetate Molecules Research Articles

Configuration of amylose acetate in dilute solution

AbstractIntrinsic viscosities of potato amylose acetate fractions have been investigated as function of temperature, solvent, and molecular weight. Relationship of viscosity with molecular weight has been established and the exponent ν in [η] = K′Mν has been discussed in the light of heterogeneity of the fractions. From the study of flexibility of the amylose acetate molecule in CH3NO2 as calculated from the effective bond length the KUHN‐KUHN equivalent chain segment length, and the ratio of the unperturbed dimension to the dimension assuming free rotation of chain units, it has been observed that amylose acetate is not as stiff as cellulose but stiffer than polystyrene. However, the values of \documentclass{article}\pagestyle{empty}\begin{document}$\overline {\cos } $\end{document}Φ indicates that the steric hindrance in the amylose chain is equal to that in the cellulose chain which is much higher than a flexible polymer chain.

Genetic control of fatty acid biosynthesis in rapeseed (Brassica napus L.)

AbstractIsolation of rapeseed plants containing no erucic acid in their seed oil gave simultaneous selection for low eicosenoic acid. Genetic analy‐sis of populations segregating for erucic acid content indicated that the synthesis of these fatty acids was controlled, in the developing embryo, by two genes which displayed no domi‐nance and acted in an additive manner. As the genetic capacity for erucic acid synthesis de‐creased, there was an increase in percentage of oleic acid with no corresponding decrease in total oil content. The percentage of eicosenoic acid re‐mained relatively constant with decreasing erucic acid except in the zero erucic acid genotype where only 1% eicosenoic was detected instead of approx 12%. These observations were in‐terpreted to mean that eicosenoic and erucic acids were formed by a genetically controlled carbon chain lengthening system operating by the addi‐tion of acetate molecules to the carboxyl end of oleic acid. This hypothesis was supported by data obtained from the injection of radioactive sodium acetate into immature rapeseed pods. In the monoene fraction of the oil, eicosenoate had three times the specific activity of oleate and erucate had twice the activity of eicosenoate. On oxidation, the monocarboxylic fragments of these three acids had low and similar specific activities while in the dicarboxylic acids, where chain elongation has presumably taken place, activity increased in the ratio of 1:5:19.

Optical anisotropy of polyvinyl acetate (PVA) molecules—III. Effect of the solvent on the internal rotation in PVA molecules

Optical anisotropy of polyvinyl acetate (PVA) molecules—III. Effect of the solvent on the internal rotation in PVA molecules

Die Biosynthese des Digitoxigenins, Herkunft des C‐20. Glykoside und Aglykone, 253. Mitteilung

AbstractMevalonic‐[3‐14C] acid (Ia) has been prepared by partial reduction of β‐hydroxy‐β‐methyl‐glutari‐[3‐14C] acid. After introduction of the ammonium salt of Ia into Digitalis lanata plants by the vick technique, crist. radioactive digitoxigenin was isolated. This contained a significant amount of radioactivity in C‐20 position. From this, together with results of former authors, it follows that the biosynthesis of digitoxigenin from mevalonic acid (probably via squalene) proceeds through a pregnane derivative. The latter needs only one molecule of acetate to form the butenolide ring.

Studies on amylose and its derivatives V — The sedimentation of amylose acetate in dilute solution

Sedimentation and viscosity measurements have been carried out on seven fractions of amylose acetate dissolved in nitromethane at a temperature of 25°C. The effect of pressure on the sedimentation constant has been investigated and the relation between S 0 0 and M W was found to be S 0 0 = 4.14 × 10 −15 bar M 0.38 W . Data obtained previously for the acetate dissolved in nitromethane, and chloroform have been reassessed using a modification of the Flory theory proposed recently by Kurata and Stockmayer, and it has been found that the amylose acetate molecule can be regarded as a flexible coil with negligible draining. The possibility of a helical form in solution is also discussed.

Homolytic copolymerization of vinyl acetate and trichlorethylene at high pressures

1. Vinyl acetate and trichlorethylene show copolymerization at atmospheric pressure. The molecular weight of the copolymer increases as the pressure is raised. The fact that the chlorine composition in the resulting copolymers is independent of pressure shows that the reduction in volume is approximately the same whether the activated complex is formed by adding the radical with the end group CH2.CHOCOCH3 to the trichlorethylene molecule or to the vinyl acetate molecule. 2. The copolymerization rate of vinyl acetate and trichlorethylene increases with increase in pressure. The value of the volume change when the activated complex is formed in the chain-breaking reaction is negative when calculated from the kinetic data, which shows that the chain-breaking is occurring in the kinetic rather than in the diffusion range.

STUDIES OF HYDRANGENOL IN HYDRANGEA MACROPHYLLA SER.: II. BIOSYNTHESIS OF HYDRANGENOL FROM C14-LABELLED COMPOUNDS

Hydrangenol-C14 was isolated from root tissues of Hydrangea macrophylla after the administration of L-phenylalanine-U-C14, -1-C14, and -3-C14, of cinnamic-2-C14, and of acetate-2-C14 and it was degraded by alkaline fusion. The distribution of labelling between two of the degradation products, 2,6-cresotic acid and p-hydroxybenzoic acid, was found to be consistent with the proposed scheme for the biosynthesis of hydrangenol, namely the condensation of an intact phenylpropanoid molecule with three molecules of acetate.

STUDIES OF HYDRANGENOL IN HYDRANGEA MACROPHYLLA SER.: II. BIOSYNTHESIS OF HYDRANGENOL FROM C14-LABELLED COMPOUNDS

Hydrangenol-C14 was isolated from root tissues of Hydrangea macrophylla after the administration of L-phenylalanine-U-C14, -1-C14, and -3-C14, of cinnamic-2-C14, and of acetate-2-C14 and it was degraded by alkaline fusion. The distribution of labelling between two of the degradation products, 2,6-cresotic acid and p-hydroxybenzoic acid, was found to be consistent with the proposed scheme for the biosynthesis of hydrangenol, namely the condensation of an intact phenylpropanoid molecule with three molecules of acetate.

Synthesis of succinate from acetate by an enzyme system of pig heart muscle.

THE oxidation and condensation of two molecules of acetate to form succinate was first proposed by Thunberg1. Many later attempts have been made to demonstrate this reaction, with for the most part equivocal results. Recently, evidence has been presented2 that the reaction does not occur in E. coli. On the other hand, evidence has been presented3,4 that extracts of Tetrahymena catalyse the Thunberg reaction at a slow rate, and Seaman5 has presented evidence that mammalian tissue catalyses the reduction of succinate to acetyl coenzyme A.

Light scattering and viscosity studies of polyvinyl acetate solutions

AbstractA light scattering photoelectric photometer was built and calibrated by a narrow fraction of polystyrene for which the molecular weight was assigned by the viscosity method. The instrument was used to determine the molecular weights of polyvinyl acetate fractions. The light scattering molecular weights of the polyvinyl acetates, up to a value of 477,000, agreed with those obtained from viscosity data employing the Nakajima equation: [η] = 8.91 × 10−3 × P0.62, where [η] is the intrinsic viscosity in benzene and P is the degree of polymerization. k′ and μ values lie in the expected ranges. The rootmean‐square end‐to‐end distances of the polyvinyl acetate molecules determined by the dissymmetry method are found to be much smaller than those calculated by Fox‐Flory relation from viscosity data.

Direct Interaction between Copper Ions in the Molecules of Copper Acetate and Propionate

EXAMINATION of the magnetic properties1 and also X-ray photographs2 showed that the crystal of copper acetate consists of molecules, Cu2(CH3COO)4.2H2O, in which a direct type of metal-to-metal interaction might be anticipated. A similar metal-to-metal interaction was proposed for copper propionate3. Recently, we have made a quantitative determination of the dichroism of microcrystals of copper formate, acetate and propionate, demonstrating the existence of the copper-to-copper linkage in the crystal of the latter two compounds, and absence of this linkage in the former.

Utilization of acetate in experimental diabetes.

IT is well known that acetic acid occupies an important place in the intermediary metabolism, and that the participation of this substance in many reactions requires the activation of the acetate molecule. It is now generally considered that ‘active acetate’ corresponds to acetyl coenzyme A. Therefore, it appears reasonable to assume that a reduction of the acetylation of coenzyme A, that is, of the formation of ‘active acetate’, would lead to the accumulation of acetic acid.

Determination of the molecular weights of fractionated polyvinyl acetates by a new type of light‐scattering instrument

AbstractA new light‐scattering instrument is described, in which the incident light beam is rotated by a mirror system, and the photomultiplier cell (E.M.I. type 5311) which measures the scattered light remains stationary. A study of the osmotic and light‐scattering molecular weights (Mw) of a series of polyvinyl acetate fractions shows that the process of fractionation separates the several molecular species present according to both size and shape. The average dimensions of the polymer chain (D) can be deduced from the dissymmetry measurements, assuming the random chain model. These results show that the most insoluble fraction has the highest molecular weight, but is also the least extended in solution. The lower‐molecular‐weight samples are relatively longer. The ratio Mw/D2 is a measure of the degree of branching of the polymer chain, and the minimum value measured for ten samples is 0.5. This is believed to be the value characteristic of the linear molecule. A photopolymer prepared at −25°C. and low conversion, that is, under conditions favoring the formation of linear polyvinyl acetate molecules, also had this same minimum value of Mw/D2 = 0.5.

Interferometric studies in diffusion. II. Influence of concentration and orientation on diffusion in cellulose acetate

The techniques developed in part I are used to study the diffusion of the five penetrants, chloroform, acetone, methylene chloride, water and methyl alcohol into stretched cellulose acetate sheet. The diffusion coefficient—concentration relationship for diffusion at right angles to the direction of stretch is obtained at 25° C for the first three penetrants and also at 40° C for chloroform. In each case a marked increase in diffusion coefficient occurs at a volume concentration of penetrant of about 60 to 70 %. The results for chloroform indicate a mean activation energy of about 6 kcal. Photographs of interferometer fringe systems in the neighbourhood of a corner of the cellulose acetate sheet are shown for each penetrant. Each photograph reveals anisotropic behaviour. This behaviour is due partly to the diffusion coefficient being less in the direction of stretch, than perpendicular to it, and partly to the overall range of concentration being less as a result of the restricted swelling of the polymer in the former direction. The degree of anisotropy is studied quantitatively for chloroform and acetone. New evidence is provided on the nature of the sharp boundaries seen under the microscope when a penetrant enters a polymer. In particular the middle boundary, which approximately indicates the concentration at which the polymer relaxes and becomes isotropic, is found to occur at avolumeconcentration of 60 to 70 % for each penetrant examined quantitatively. On inspecting a model of a cellulose acetate molecule it seems likely that at this volume concentration the polymer chains are sufficiently well separated to allow one repeating unit of the polymer chain to rotate about the axis of the chain without hindrance from neighbouring chains. An analogy with second-order transition phenomena is drawn.

On the Shape of Amylose Acetate Molecule

On the Shape of Amylose Acetate Molecule

On the Structure of Cellulose Acetate Molecules in Acetone Solution

Data obtained from sedimentation velocity and viscosity measurements on a series of cellulose acetate fractions in acetone are interpreted in terms of two models, the impenetrable ellipsoid of rotation and the uniform density random coil. The lack of agreement using the former model is shown to be a real effect, rather than one determined by experimental inaccuracy. As other investigations have revealed, the uniform density random coil is not a satisfactory model for these molecules either. Probably the best hydrodynamical model for these and other extended but not perfectly rigid molecules in solution is a penetrable ellipsoid of rotation.

Determination of the velocity coefficients for polymerization processes. - I. The direct photopolymerization of vinyl acetate

This paper describes a method whereby the individual velocity coefficients of a vinyl polymerization reaction have been determined by a detailed analysis of the kinetics of the photo-polymerization of liquid vinyl acetate. The evaluation of the coefficients is made by the development of an accurate method for measuring the lifetime of the active polymeric molecules employing intermittent radiation. In addition, the kinetic chain length and the number average molecular weight of the polymers have been measured. It is shown that each absorbed quantum of radiation activates one vinyl acetate molecule probably as a diradical. The chain terminates by a disproportionation reaction between the polymer radicals. The size of the growth or propagation bimolecular coefficient decreases only slightly as the molecule grows, the energy of activation is 4400 cal. and the steric factor of the growth reaction is 10 -5 . In the termination reaction there is likewise only a small decrease of velocity coefficient with increasing molecular size—no energy of activation is required and the steric factor has the surprisingly large value of 10 -2 .