Isomeric Change Research Articles

Ultrasonic relaxation in liquid C5-C10, C12 and C14 n-alkanes

Ultrasonic absorption has been measured in liquid n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-dodecane and n-tetradecane, over the temperature range from –40°C or the melting point to 25°C and frequency range 15 to 230 MHz. A relaxation observed in the four higher members of this series has been discussed in terms of rotational isomeric processes. The important feature of the results is that the frequency of the acoustically active conformation change decreases with increasing chain length. The variation is similar to that expected for the first normal mode of motion of a chain of damped torsional oscillators. The ratio of compressional to shear viscosities in these systems decreases with increasing chain length, again indicating that a rotational isomeric change of finite volume change is involved in both shear and compressional relaxation.

Kinetic and Equilibrium Studies ond-Glucose-d-Fructose Isomerization Catalyzed by Glucose Isomerase fromStreptomycessp.

The equilibrium constant of the isomerization reaction between d-glucose and d-fructose which is catalyzed by a. glucose isomerase from Streptomyces sp. was obtained by both methods of chemical analysis and of kinetic study over the temperature range of 25° to 70°C. It was found that the formation of d-fructose from d-glucose was an endothermic reaction with the heat of the reaction, ΔH, of +2220 cal/mole. The standard free energy change, ΔG, and the standard entropy change, ΔS, associated with the isomeric change were found to be +180 cal/mole and + 6.8 cal/deg. mole at 25°C, respectively. The values of these thermodynamic quantities at other temperature are also summarized.

Inhibition of glycosidases by aldonolactones of corresponding configuration: Preparation of (1→5)-lactones by catalytic oxidation of pyranoses and study of their inhibitory properties

1. A method was devised for the preparation of (1-->5)-lactones from pyranose sugars and uronic acids by platinum-catalysed oxidation with gaseous oxygen in aqueous solution at acid pH. It was applied to mannose, N-acetylglucosamine, N-acetylgalactosamine, glucuronic acid, galacturonic acid, galactose, l-arabinose and d-fucose. 2. Only the first three yielded products that could be obtained in the solid state without decomposition. In every case, however, the oxidation product in aqueous solution behaved as the aldono-(1-->5)-lactone, and was more inhibitory towards the appropriate glycosidases than any aldonolactone preparation hitherto examined. 3. The stabilities of the oxidation products were studied, and their interconversion with the (1-->4)-lactones was demonstrated. Ring-opening does not appear to be mandatory for this isomeric change, which in some instances is very rapid. 4. To explain all the inhibitory effects observed with aldonolactones on glycosidases of corresponding configuration, it is tentatively postulated that inhibition may be due entirely to the (1-->5)-lactone, and that any inhibitory effect seen with the (1-->4)-lactone is a measure of the extent and speed of its conversion into the (1-->5)-lactone in aqueous solution.

Kinetic and Equilibrium Studies on D-Glucose-D-Fructose Isomerization Catalyzed by Glucose Isomerase from Streptomyces sp.

The equilibrium constant of the isomerization reaction between d-glucose and d-fructose which is catalyzed by a. glucose isomerase from Streptomyces sp. was obtained by both methods of chemical analysis and of kinetic study over the temperature range of 25° to 70°C. It was found that the formation of d-fructose from d-glucose was an endothermic reaction with the heat of the reaction, ΔH, of +2220 cal/mole. The standard free energy change, ΔG, and the standard entropy change, ΔS, associated with the isomeric change were found to be +180 cal/mole and + 6.8 cal/deg. mole at 25°C, respectively. The values of these thermodynamic quantities at other temperature are also summarized.

A Comparison of the Isomeric Changes in the Induced and Spontaneous Aquation of Ions of the Type CoIII(en)2YX

A Comparison of the Isomeric Changes in the Induced and Spontaneous Aquation of Ions of the Type Co^III(en)₂YX

Gamboge. Part II

The isolation of gambogic acid is described. Reactions of gambogic acid are discussed and it is shown that some reactions involve isomeric change in the molecule. The possible relationship of gambogic acid to morellin is considered, the substitution pattern being examined in detail, and a structure is assigned which is consistent with much of the known chemistry of gambogic acid.

The ultraviolet spectra of aromatic hydrocarbons: Predicting substitution and isomerism changes

Presents a theory that allows one to predict the UV spectra of many benzene derivatives and their isomers.

METHYLENE VIOLET (BERNTHSEN), BY ZINC-ALKALI-CHLORATE HYDROLYSIS OF METHYLENE BLUE.

Though Bernthsen's methylene violet (MV) is a common constituent of polychrome methylene blue, the hydrolytic oxydation of methylene blue to yield azure-free MV has been considered a difficult chemical reaction since the time of Bernthsen, who used Ag2O in the hydrolysis. MV is qualitatively distinguished from azures by Bernthsen's criteria and the author's new tests: (1) light-excited isomeric change, (2) reactivity to acidity, (3) reaction with KCIO, and (4) reaction with Na2SO3 of azures in CHCI3, while MV gives none. But MV shows (5) indicator properties at pH 4, while azures do not. For practical hydrolysis, treat methylene blue (10 parts by weight) and KCIO3 (1 part) with 1-2 N NaOH to convert methylene blue to a mixture of MV and azures. Then dilute the solution, add a Zn salt and NaHCO3 in excess of the amount needed to convert the NaOH to Na2CO3. Boil the solution gently for 1-2 hr. The end point of the reaction is found by pipetting a drop of reactant into 3% acetic acid in a test tube, adding CHC13 and extracting. The acetic layer should then be almost colorless while the CHC13 is colored intensely cherry red. After cooling, the precipitated dye is filtered and dried. This procedure gives good yields of a dye which meets the criteria given by Bernhsen. The peak of the absorption curve in solution, pH 4-11, is at 624 mμ (Bernthsen 625 mμ) and in acid solution, pH 0-4, 588 mμ (Biological Stains, 1953; 580 μ). The dye contains so little azures, that purification of the MV fraction obtained from the reaction mixture is unnecessary when it is used in the Wright-type Romanowsky stain. The remarkable staining effect of MV is its power to bring out red azurophil granules of monocytes and lymphocytes when used with eosinated thiazins in Wright's stain.

Preparation of anthocyanidins and their glygosides from related flavonoids

Improvements in the method of reductive acetylation of flavonols provide pure samples of anthocyanidins, the examples studied being cyanidin and its O-pentamethyl and O-5,7,3′,4′-tetramethyl derivatives. The method can also be used for the conversion of flavonol glycosides into anthocyanins; the preparation of cyanidin and pelargonidin-3-rhamnoglucosides are described. 3-Hydroxyflavanones, e.g. taxifolin, aromadendrin and dihydrorobinetin undergo isomeric change into ψ-base acetates of anthocyanidins on heating at 150–155° with acetic anhydride solution and a base catalyst and the ψ-base acetates undergo conversion into anthocyanidins in very good yields. The mechanism of this transformation is made clear by the isolation of intermediate stages in the case of taxifolin tetramethyl ether. This result suggests the possibility of a direct route for the biogenesis of 3-hydroxy anthocyanidins from the 3-hydroxy flavanones. But this change has not so far been successfully carried out with flavanones not having the 3-hydroxyl. Flavones, e.g. apigenin and its trimethyl ether, yield on reductive acetylation, a mixture of products, in which flavenes seem to be predominant. The intermediates undergo conversion into apigeninidin chloride and its O-trimethyl derivative in good yields. 2′-Hydroxy-4,4′,6′-trimethoxy dibenzoyl methane on reduction with borohydride gives the diol which undergoes conversion in acids satisfactorily to apigeninidin trimethy] ether. Substituted flavan-4-ols, prepared by reduction of a flavanone, give the corresponding anthocyanidins (yield ca. 10 per cent) on heating in alcoholic hydrochloric acid.

Derivatives of 1,4-dioxo-cyclohexane as possible intermediates in isomeric changes dependent on cobamide coenzymes.

Derivatives of 1,4-Dioxo-Cyclohexane as Possible Intermediates in Isomeric Changes Dependent on Cobamide Coenzymes

Ring-isomeric change in isoflavones : Synthesis of 5,7-dimethoxy-6-hydroxyisoflavone, muningin and 5,7-dihydroxy-6-methoxyisoflavone

The above mentioned compounds have been prepared by methods involving isomeric change from the more readily available 5,7,8-substituted isoflavones.

Synthetic experiments in the benzopyrone series

8-Methyl baicalein has been made (1) from 8-methyl chrysin by the preparation of the 6-aldehyde and subsequent Dakin's reaction and (2) from C-methyl phloracetophenone dimethyl ether by steps involving persulphate oxidation and flavone ring closure. The isomeric 6-methyl compound has been obtained by the nuclear methylation of norwogonin and demethylation with aluminium chloride. The methyl ethers of the former undergo only demethylation when boiled with hydriodic acid whereas those of the latter undergo isomeric change besides demethylation.

Syntheses in the quinazolone series—VI: The synthesis of 1:2:3:4-tetrahydro-2-aryl-4-oxoquinazolines

An investigation of the isomeric change of N 2-arylideneorthanilamides has led to the synthesis of a new series of 1:2:3:4-tetrahydro-4-oxoquinazolines from which the corresponding quinazol-4-ones have been obtained by oxidation. Based on the present investigation, a new synthesis of 2-( o-aminophenyl)-3 H-quinazol-4-one (VI) is also reported.

Mechanism of the catalytic polymerization of propene under pressure

1. It was established that, unlike the polymerization of propene over phosphoric acid (which proceeds by simple stepwise addition of propene), its polymerization over zinc chloride is accompanied by isomeric changes which result in the formation of hydrocarbons containing quaternary carbon atoms. 2. It was shown that, apart from trialkylalkenes containing quaternary carbons or three consecutive tertiary carbons, the propene trimers included also dialkylalkenes (3,4-dimethyl- 3-heptene, 2,6-dimethyl- 2-heptene, and 4,6-dimethyl-1-heptene) and the monoalkylalkene 7-methyl-3-octene. 3. The formation of only slightly branched olefins indicates that in the polymerization of propene isomeric changes occur, not only in the direction of the formation of highly branched forms, but also in the reverse direction, with conversion of highly branched forms into only slightly branched forms according to the mechanism of isomeric transformations in the corresponding carbonium ions.

Low-temperature alkylation of ?- and ?- olefins with tertiary alkyl halides in presence of zinc chloride

1. A study was made of low-temperature alkylation of olefine with tertiary alkyl halides in presence of zinc chloride, and the relationship between the structure of the reactants and the character of the side reactions — isomeric changes accompanying the reaction of addition of chloroalkans to alkaŋes — was elucidated. 2. It was established that in the alkylation of 2-butene, both with tert-butyl chloride and with 2-chloro-2, 3-dimethylbutane. the octene and decene isomers predicted by theory are formed. 3. I the alkylation of 2-methyl-2butene with tert-butyl chloride, only one isometric form of the expected structure is formed (2,3,3,4-tetramethyl-4-heptene), and in alkylation with 2-chloro-2,3,3-trimethylbutane, again only one isomeric form (2,3,3,4,40pentamethyl-1-hexene).

Dehydrochlorination of trichloro(chloroalkyl)- and trichloro(dichloroalkyl)-silanes. Rearrangement of 1,1,1,2,4,4,4-heptachloro-1,4-dislabutane during dehydrochlorination with aluminum chloride

1. The dehydrochlorination of the following compounds was carried out for the first times With the aid of quinolines Cl2SiCH2CHClCH2, Cl2SiCH2CCl(CH2)2 and Cl2SiCHClCH2SiCl2. With the aid of aluminum chloride: 1,1- 1,2- and 2,2-dichloroethyltrichlorosilanes, Cl2SiCH2CH (CH2)CH2Cl and Cl2SiCHClCH2SiCl2. 2. It was shown that, when quinolines was used, dehydrochlorination products were obtained in high yield only when the chlorine atom was in the\gb-position with respect to silicon, the products being exclusively 1-alkenylsilanes. Aluminum chloride can be applied for dehydrochlorination only in the case of trichlorochloroalkyl)silanes, but the chlorine atom may be in the\ga-,\gb-, or\gg-position. 3. A new arrangement in organosilicon chemistry was discovered. In the dehydrochlorination of 1-chloro-1,2-bistrichlorosillylethane (1,1,2,4,4,4-heptachloro-1,4-disilabutane) with quinoline, only 1,2-bistrichlorosilylethylene was formed, whereas in dehydrochlorination with aluminum chloride the same product was obtained in admixture with 1,1-bistrichlorosilylethylene. A scheme is given in which an isomeric change in the skeleton of the original compound occurs in the course of the dehydrochlorination.

Ultrasonic Propagation and Its Relation to Molecular Structure in the Diols

Measurements of viscosity, ultrasonic absorption, and velocity were made in a group of associated organic liquids, known as the diols. Included in the measurements were ethanediol, two isomers of propanediol, and three isomers of butanediol. In these liquids the values of absorption ranged from 1.66 to 2.20 times that value calculated from Stokes formula. The effect of the structural differences indicated the following, when the addition of CH2 groups was considered, (1) an increase in shear viscosity, (2) an increase in adiabatic compressibility, (βad), and (3) an increase in the ratio of αobs/αcalc. Effects caused by isomeric changes were (1) an increase in βad and (2) an increase in αobs/αcalc as the (OH) groups were brought closer together. It was concluded that a relationship existed between the ratio of αobs/αcalc and βad. Measurement of absorption vs temperature in ethanediol over a viscosity range of 24:1 indicated that the difference in activation energy of shear and compressional viscosity could be no greater than 0.1 percent.

Thermochemical investigation of isomeric platinum compounds

1. A method has been proposed for the determination of the differences between the total energies of isomeric platinum chloroammines. 2. A hermetic calorimeter for liquids, having constant heat exchange and permitting measurements to be taken from room temperature to 100–120°, has been constructed. The thermometer of the calorimeter has a sensitivity of the order of 5 · 10−6. The calorimetric sensitivity of the apparatus is 1.5 · 10−8 cal. The amount of complex compound required for the measurement is 0.1 – 0.3 g. 3. Measurements have been made of the heats of reaction of five chloroammines of bivalent platinum with aqueous ammonia (9.4% NH2) at 70°, the probable error being about 1%. The heats of four isomeric changes have been estimated (probable error about 10%).

Synthesis of isocarajuretin hydrochloride

7-Hydroxy-5:8:4′-trimethoxy flavylium chloride has now been prepared and subjected to demethylation with hydriodic acid. The resulting flavylium iodide and the colour-base (Isocarajuretin) and the flavylium chloride obtained from it, are different from carajuretin and its salts. Hence it is concluded that no isomeric change takes place during the demethylation of derivatives of 5:7:8-hydroxy-flavylium salts related to flavones, supporting the constitution of carajurin, given by Chapman, Perkin and Robinson.

Nuclear oxidation in flavones and related compounds

Using methods of nuclear oxidation 7 : 8-dihydroxy-2-methyl isoflavone, 5 : 7 : 8-trihydroxyisoflavone and 5 : 7 : 8-trihydroxy-2-methyl isoflavone and their derivatives have been prepared. Demethylation of the 5 : 7 : 8-trimethoxy isoflavones with or without a 2-methyl group does not produce isomeric change in the trihydroxy product. It could therefore be concluded that a phenyl group in the 3-position prevents this isomeric change just like a methoxyl (hydroxyl) in the same position and that substitution in the 2-position has no influence.