Partial methylation of methyl α-D- and β-D-threofuranoside

1990 ◽  
Vol 55 (7) ◽  
pp. 1777-1782 ◽  
Author(s):  
Jiří Jarý ◽  
Miroslav Marek ◽  
Ivan Raich
Keyword(s):  
Sodium Hydroxide ◽  
Methyl Iodide ◽  
Rate Constants ◽  
Relative Rate ◽  
Hydroxyl Groups ◽  
Partial Methylation ◽  
Methylation Rate ◽  
Consecutive Reactions ◽  
Relative Rate Constants ◽  
The Individual

The methylation rate of hydroxyl groups of the title glycosides I and II has been studied in their reaction with methyl iodide and sodium hydroxide in acetonitrile. From the relative rate constants determined for the side and consecutive reactions taking place the differences in methylation rate of the individual hydroxyl groups have been deduced and are discussed from the standpoint of possible steric and polar effects.

Partial methylation of methyl 2,6-dideoxy-α-D-xylo- and α-D-lyxo-hexopyranoside

1981 ◽  
Vol 46 (10) ◽  
pp. 2410-2420 ◽  
Author(s):  
Jiří Jarý ◽  
Miroslav Marek
Keyword(s):  
Sodium Hydroxide ◽  
Methyl Iodide ◽  
Rate Constants ◽  
Relative Rate ◽  
Reaction Rates ◽  
Steric Effects ◽  
Side Reactions ◽  
Hydroxyl Groups ◽  
Partial Methylation ◽  
Relative Rate Constants

Rate of methylation of the hydroxyl groups in the title glycosides was investigated during their reaction with methyl iodide and sodium hydroxide in acetonitrile. Relative rate constants of the side-reactions and subsequent reactions taking place were calculated. The differences in the reaction rates of methylation of individual hydroxyl groups are discussed in connection with the possible polar and steric effects.

Selective Accessibilities of Hydroxyl Groups in the Microstructure of Cotton Cellulose

1969 ◽  
Vol 39 (6) ◽  
pp. 530-542 ◽  
Author(s):  
S. P. Rowland ◽  
E. J. Roberts ◽  
C. P. Wade
Keyword(s):  
Sodium Hydroxide ◽  
Rate Constants ◽  
Relative Rate ◽  
Heterogeneous Systems ◽  
Heterogeneous Reactions ◽  
Cotton Cellulose ◽  
Hydroxyl Groups ◽  
Relative Rate Constants ◽  
The Individual ◽  
Liquid Chromatographic

The reactions of 2-chloroethyldiethylamine with the hydroxyl groups at C-2, C-3, and C-6 of the d-glucopyranosyl unit of cotton cellulose were investigated as a means of evaluating the relative accessibilities of these hydroxyl groups in heterogeneous reactions of fibrous cellulose. The relative rate constants for reactions of the individual types of hydroxyl groups were determined from reactions of cellulose in solution and from reactions of disordered cellulose in heterogeneous systems. Quantitative determinations of the distributions of 2-(diethylamino)ethyl substituents in the mono-substituted d-glucopyranosyl units involved hydrolysis of the chemically modified cellulose to glucose and substituted glucoses followed by gas-liquid chromatographic analysis. The relative accessibilities of the hydroxyl groups at C-2 and C-3 vs those at C-6 were estimated for crystalline celluloses by employing the relative rate constants (noted above) together with the experimentally measured distributions of substituents resulting from heterogeneous reactions of crystalline celluloses and appropriate kinetic expressions. The relative accessibilities of the hydroxyl groups at C-2, C-3, and C-6 in cellulose in strong mercerizing media approach those of cellulose in solution. In media of lower concentration of sodium hydroxide (i.e., 4 N or 13.9%), selective accessibilities of the individual types of hydroxyl groups become evident, and these selective accessibilities become pronounced in sodium hydroxide solutions of still lower concentrations (e.g., N and 2 N).

Partial methylation of methyl 4,6-dideoxy-α- and β-L-ribo-hexopyranosides

1984 ◽  
Vol 49 (9) ◽  
pp. 2130-2140 ◽  
Author(s):  
Karel Kefurt ◽  
Zdeňka Kefurtová ◽  
Jiří Jarý
Keyword(s):  
Gas Chromatography ◽  
Ir Spectra ◽  
Sodium Hydroxide ◽  
Methyl Iodide ◽  
Rate Constants ◽  
Hydroxyl Groups ◽  
View Point ◽  
Partial Methylation ◽  
H Nmr ◽  
Analogous Data

Anomeric methyl 4,6-dideoxy-L-ribo-hexopyranosides I and V, prepared from aldose IX, were etherified with methyl iodide in acetonitrile in the presence of sodium hydroxide. From the products of partial methylation methyl 4,6-dideoxy-2-O-methyl-α-L-ribo-hexopyranoside (II) and methyl 4,6-dideoxy-2,3-di-O-methyl-α-L-ribo-hexopyranoside (IV), or methyl 4,6-dideoxy-2-O-methyl-β-D-ribo-hexopyranoside (VI) and methyl 4,6-dideoxy-2,3-O-methyl-β-L-ribo-hexopyranoside (VIII), respectively, were isolated. The substances were identified by 1H NMR, mass and IR spectra and comparison with standards. The course of etherification of glycosides I and V was checked by gas chromatography and the reactivity of the hydroxyl groups was evaluated by determining the rate constants or their ratios. The observed values were compared with analogous data for other isomers of methyl 4,6-dideoxyhexopyranosides and discussed from the view-point of sterical and polar influence on the reactivity of both their hydroxylic groups.

Kinetics of Methylation of Methyl 5-Deoxy-α/β-D-xylofuranosides

2004 ◽  
Vol 69 (10) ◽  
pp. 1877-1888
Author(s):  
Mária Oščendová ◽  
Jitka Moravcová
Keyword(s):  
Sodium Hydroxide ◽  
Methyl Iodide ◽  
Rate Constants ◽  
Reaction Rate ◽  
Steric Effect ◽  
Order Reaction ◽  
Half Time ◽  
First Order ◽  
Consecutive Reactions ◽  
Kinetics Of

The kinetics of methylation of methyl 5-deoxy-α-D-xylofuranoside (1), methyl 5-deoxy-β-D-xylofuranoside (2) and their partly methylated derivatives with methyl iodide in the presence of sodium hydroxide in acetonitrile was studied. The reaction rate was independent of the base concentration during the first half-time only and the methylation proceeded as a first-order reaction. The rate constants of all side and consecutive reactions were calculated and the influence of both polar and steric effect is discussed. The methylation of 1 was highly regioselective giving almost exclusively 5-deoxy-2-O-methyl-α-D-xylofuranoside.

Reactivity of hydroxyl groups of 1,6 : 2,3- and 1,6 : 3,4-dianhydrido-β-D-hexapyranoses in methylation with iodomethane

1988 ◽  
Vol 53 (3) ◽  
pp. 633-637 ◽  
Author(s):  
Stanislav Sámek ◽  
Tomáš Trnka ◽  
Miloslav Černý
Keyword(s):  
Hydrogen Bonds ◽  
Rate Constants ◽  
Silver Oxide ◽  
Relative Rate ◽  
Steric Effects ◽  
Hydroxyl Groups ◽  
Intramolecular Hydrogen Bonds ◽  
Relative Rate Constants ◽  
Intramolecular Hydrogen

Relative rate constants for reaction of 1,6 : 2,3- and 1,6 : 3,4-dianhydro-β-D-hexapyranoses with iodomethane in acetonitrile in the presence of silver oxide were measured. Their values, ranging from 1 to 8.6 were interpreted on the basis of polar and steric effects and intramolecular hydrogen bonds.

Kinetics of the successive chlorination of 1,2-dichloroethane in the liquid phase

1969 ◽  
Vol 22 (6) ◽  
pp. 1177 ◽  
Author(s):  
DS Caines ◽  
RB Paton ◽  
DA Williams ◽  
PR Wilkinson
Keyword(s):  
Liquid Phase ◽  
Rate Constants ◽  
Relative Rate ◽  
Stirred Tank ◽  
Continuous Stirred Tank Reactor ◽  
Alternative Pathways ◽  
Tank Reactor ◽  
Relative Rate Constants ◽  
Continuous Stirred Tank ◽  
Kinetics Of

Liquid 1,2-dichloroethane has been chlorinated by dissolved chlorine to a succession of chloroethanes up to the ultimate hexachloroethane. The results of both batch and continuous stirred tank reactor systems have been analysed by computer techniques to give a set of relative rate constants from which one can predict the product composition for a given chlorine uptake, the aim in this work being to optimize the production of tetrachloroethanes. An unusual feature of the kinetics is that 1,1,1,2- and 1,1,2,2-tetrachloroethanes provide alternative pathways between 1,1,2-trichloroethane and pentachloroethane.

RECOMBINATION OF OPPOSITELY CHARGED AQUEOUS CLUSTER IONS USING ELECTROSTATICALLY MERGED ION BEAMS

1996 ◽  
Vol 03 (01) ◽  
pp. 655-660 ◽  
Author(s):  
B. PLASTRIDGE ◽  
K.A. COWEN ◽  
D.A. WOOD ◽  
M.H. COHEN ◽  
J.V. COE
Keyword(s):  
Rate Constants ◽  
Cluster Size ◽  
Collision Energy ◽  
Relative Rate ◽  
Center Of Mass ◽  
Cluster Ions ◽  
Charged Cluster ◽  
Relative Rate Constants ◽  
Oppositely Charged ◽  
Electrostatic Quadrupole

A new method for studying cluster-cluster interactions is introduced which involves merging mass-selected beams of oppositely charged cluster ions with an electrostatic quadrupole deflector. Recombination is monitored by measuring the rate of fast neutral production. Relative rate constants have been measured for the reaction of H 3O+( H 2 O )n+ OH −( H 2 O )m as a function of cluster size (m=n=0–3), which display a pronounced enhancement with clustering. Relative rate constants have also been measured as a function of center-of-mass collision energy for a heavily clustered reaction (n=3, m=3) and a lightly clustered reaction (n=1, m=0) revealing that clustering produces a dramatic change in the reaction mechanism.

REACTION OF OXYGEN ATOMS WITH BUTADIENE

1960 ◽  
Vol 38 (11) ◽  
pp. 2187-2195 ◽  
Author(s):  
R. J. Cvetanović ◽  
L. C. Doyle
Keyword(s):  
Pressure Dependence ◽  
Rate Constants ◽  
Room Temperature ◽  
Relative Rate ◽  
Excess Energy ◽  
General Mechanism ◽  
Arrhenius Parameters ◽  
Heats Of Reaction ◽  
Relative Rate Constants ◽  
Oxygen Atoms

Reaction of oxygen atoms with 1,3-butadiene has been investigated at room temperature. It is found that it conforms to the general mechanism established previously for the analogous reactions of monoolefins. Only 1,2-addition occurs, and the addition products, butadiene monoxide and 3-butenal, possess excess energy when formed as a result of high heats of reaction. The pressure dependence of the formation of the addition products yields the values of the "lifetimes" of the initially produced "hot" molecules. The relative rate constants have been determined at 25 and 127 °C and from these the relative values of the Arrhenius parameters have been calculated.

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