Derivatives of 2-Mercaptobenzothiazole and Dimethyldithiocarbamic Acid as Vulcanization Accelerators

1959 ◽  
Vol 32 (4) ◽  
pp. 983-991 ◽  
Author(s):  
M. S. Fel'dshteĭn ◽  
I. I. Eĭtingon ◽  
D. M. Pevzner ◽  
N. P. Strel'nikova ◽  
B. A. Dogadkin
Keyword(s):  
Functional Groups ◽  
Chemical Structure ◽  
Practical Interest ◽  
Hydroxyl Group ◽  
Carboxyl Group ◽  
Methyl Radical ◽  
Methyl Derivative ◽  
Great Practical Interest ◽  
Analogous Functional ◽  
Derivatives Of

Abstract 1. We have synthesized and investigated as vulcanization accelerators the derivatives of 2-mercaptobenzothiazole (MBT) in which the thiol hydrogen is replaced by the nonpolar methyl radical, as well as compounds in which methyl hydrogen of the methyl derivative is replaced by various functional groups. 2. It has been shown that methyl-2-thiolbenzothiazole is not an accelerator. The replacement in this compound of one of the methyl hydrogens by a polar hydroxyl group substantially enhances the activity (see, however, editors note in the text). The substitution of hydrogen by a carboxyl group does not increase vulcanizing activity. 3. We have determined that replacement of a methyl hydrogen by an amino radical increases sharply the accelerating activity. The structure obtained as a result of this reaction, benzothiazolyl-2-thiolmethyldiethylamine (BTMA), is of great practical interest as an accelerator. 4. The accelerator BTMA in stocks of natural and SKS rubber gives vulcanizates which are substantially superior in their properties to rubbers cured with MBT, and are practically equal to vulcanizates obtained with sulfenamide accelerators—sulfenamide BT and sulfenamide Z (Santocure). 5. The accelerator BTMA is much cheaper than sulfenamide BT since its production requires much less diethylamine. 6. It has been determined that, just as in the case of 2-mercaptobenzothiazole derivatives, for the derivatives of dimethyldithiocarbamic acid containing analogous functional groups the same results are obtained for the change in activity depending upon the chemical structure of the accelerator.

scholarly journals New bio-amphiphilic structures of sucrose via amides linkages

2019 ◽  
Vol 10 (4) ◽  
pp. 3143-3154
Author(s):  
Salih Mahdi Salman
Keyword(s):  
Chemical Structure ◽  
13C Nmr Spectroscopy ◽  
Alkyl Halides ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Staudinger Reaction ◽  
Target Structure ◽  
Leaving Group ◽  
Derivatives Of ◽  
Resolution Mass

A series of four new derivatives of sucrose have been synthesized using the straightforward methodology in order to give a mono substituted analogs of sucrose at C-6’ of fructose moiety. The synthesis was started from the reaction of sucrose with tert-butylchlorodiphenylsilane, which is able to react with an only less steric hindrance hydroxyl group at C-6’ due to its bulky structure. The other hydroxyl groups were acetylated by the reaction with acetic anhydride in pyridine. Then free the hydroxyl group at C-6’ again by the treatment with t-butylammonium fluoride in THF. The later was activated by conversion to a good leaving group via tosylation, followed by functionalized via azidation to give the precursor of the target series hepta-O-acetyl-6’-azido- sucrose. The precursor was coupled with four alkyl halides (C12, C8-4, C14, C10-8) via Staudinger reaction to produced the target structure after deacetylating. The purity and chemical structure of the synthesized compound was confirmed by CHN elemental analysis, high-resolution mass and 1H, 13C NMR spectroscopy. 

Inductive effect in EI-mass spectra of some 5,6-dihalogenides and 5,6-halohydrins of 5α-cholestan-3β-ol and 3β-acetoxy-5α-cholestane

1982 ◽  
Vol 47 (11) ◽  
pp. 2946-2960 ◽  
Author(s):  
Antonín Trka ◽  
Alexander Kasal
Keyword(s):  
Mass Spectra ◽  
Inductive Effect ◽  
Molecular Ions ◽  
Hydroxyl Group ◽  
Halogen Atoms ◽  
Derivatives Of

Partial EI-mass spectra of 3β-hydroxy- and 3β-acetoxy-5α-cholestanes substituted in positions 5α-, 6β- or 5α,6β- with a hydroxyl group or halogen atoms (fluorine, chlorine, bromine) are presented. The molecular ions of 5α,6β-disubstituted derivatives of 3β-hydroxy-5α-cholestane (or of its 3-acetate) are considerably more stable than the corresponding monosubstituted derivatives if at least one of the pair of the vicinal substituents is chlorine or fluorine. This increase in stability, most striking in 5α- and 6β-fluoro compounds, is explained by the inductive effect.

Some 2-substitution derivatives of 5-(4-oxo-6-hydroxy-3,4-dihydro-5-pyrimidinyl)pentanoic acid

1983 ◽  
Vol 48 (1) ◽  
pp. 304-311 ◽  
Author(s):  
Jiří Křepelka ◽  
Jan Beneš ◽  
Vladimír Pouzar ◽  
Jaroslav Vachek ◽  
Jiří Holubek
Keyword(s):  
Nitrile Group ◽  
Antineoplastic Activity ◽  
Carboxyl Group ◽  
Positional Isomers ◽  
Pentanoic Acid ◽  
Pharmacological Tests ◽  
Derivatives Of

Condensation of triethyl ester of 1,1,5-pentanetricarboxylic acid (XI) with substituted guanidines XXII - XXIX gave acids II - IX, which were converted into esters XI - XIX. The acid II and the ester XI were obtained as mixtures of positional isomers. Analogously, condensation of the triester XXI with dicyanodiamide gave rise to acid X, whose nitrile group, under conditions of esterification of a carboxyl group, produced iminoether XX. In pharmacological tests for antineoplastic activity the compounds prepared exhibited weaker efficacy than 5-(2-amino-6-hydroxy-4-oxo-3,4-dihydro-5-pyrimidinyl)pentanoic acid (I), employed as standard.

scholarly journals Reactivity of Aliphatic and Phenolic Hydroxyl Groups in Kraft Lignin towards 4,4′ MDI

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2131
Author(s):  
Leonardo Dalseno Antonino ◽  
Júlia Rocha Gouveia ◽  
Rogério Ramos de Sousa Júnior ◽  
Guilherme Elias Saltarelli Garcia ◽  
Luara Carneiro Gobbo ◽  
...  
Keyword(s):  
Experimental Work ◽  
Chemical Structure ◽  
31P Nmr ◽  
Kraft Lignin ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Diphenylmethane Diisocyanate ◽  
Complex Chemical ◽  
Heterogeneous Reactivity ◽  
Phenolic Hydroxyl Groups

Several efforts have been dedicated to the development of lignin-based polyurethanes (PU) in recent years. The low and heterogeneous reactivity of lignin hydroxyl groups towards diisocyanates, arising from their highly complex chemical structure, limits the application of this biopolymer in PU synthesis. Besides the well-known differences in the reactivity of aliphatic and aromatic hydroxyl groups, experimental work in which the reactivity of both types of hydroxyl, especially the aromatic ones present in syringyl (S-unit), guaiacyl (G-unit), and p-hydroxyphenyl (H-unit) building units are considered and compared, is still lacking in the literature. In this work, the hydroxyl reactivity of two kraft lignin grades towards 4,4′-diphenylmethane diisocyanate (MDI) was investigated. 31P NMR allowed the monitoring of the reactivity of each hydroxyl group in the lignin structure. FTIR spectra revealed the evolution of peaks related to hydroxyl consumption and urethane formation. These results might support new PU developments, including the use of unmodified lignin and the synthesis of MDI-functionalized biopolymers or prepolymers.

scholarly journals Combustion and gasification characteristics of low-temperature pyrolytic semi-coke prepared through atmosphere rich in CH4 and H2

2021 ◽  
Vol 10 (1) ◽  
pp. 189-200
Author(s):  
Yuan She ◽  
Chong Zou ◽  
Shiwei Liu ◽  
Keng Wu ◽  
Hao Wu ◽  
...  
Keyword(s):  
Functional Groups ◽  
Chemical Structure ◽  
Nitrogen Adsorption ◽  
Inhibitory Effect ◽  
X Ray ◽  
Coke Reactivity ◽  
Reducing Gas ◽  
Reactivity Indexes ◽  
Infrared Spectrometer ◽  
Reducing Gases

Abstract Thermoanalysis was used in this research to produce a comparative study on the combustion and gasification characteristics of semi-coke prepared under pyrolytic atmospheres rich in CH4 and H2 at different proportions. Distinctions of different semi-coke in terms of carbon chemical structure, functional groups, and micropore structure were examined. The results indicated that adding some reducing gases during pyrolysis could inhibit semi-coke reactivity, the inhibitory effect of the composite gas of H2 and CH4 was the most observable, and the effect of H2 was higher than that of CH4; moreover, increasing the proportion of reducing gas increased its inhibitory effect. X-ray diffractometer and Fourier-transform infrared spectrometer results indicated that adding reducing gases in the atmosphere elevated the disordering degree of carbon microcrystalline structures, boosted the removal of hydroxyl- and oxygen-containing functional groups, decreased the unsaturated side chains, and improved condensation degree of macromolecular networks. The nitrogen adsorption experiment revealed that the types of pore structure of semi-coke are mainly micropore and mesopore, and the influence of pyrolytic atmosphere on micropores was not of strong regularity but could inhibit mesopore development. Aromatic lamellar stack height of semi-coke, specific surface area of mesopore, and pore volume had a favorable linear correlation with semi-coke reactivity indexes.

Preparation of Water-Soluble Carboxymethylated Lignin from Wheat Straw Alkali Lignin

2012 ◽  
Vol 550-553 ◽  
pp. 1293-1298 ◽  
Author(s):  
Lin Huo Gan ◽  
Ming Song Zhou ◽  
Xue Qing Qiu
Keyword(s):  
Wheat Straw ◽  
Acid Concentration ◽  
1H Nmr Spectroscopy ◽  
Water Soluble ◽  
Monochloroacetic Acid ◽  
Hydroxyl Group ◽  
Carboxyl Group ◽  
Optimum Conditions ◽  
Alkali Lignin ◽  
Carboxyl Group Content

Water-soluble carboxymethylated lignin (CML) was synthesized using wheat straw alkali lignin (WAL) in aqueous medium. The process of carboxymethylation was optimized with respect to the NaOH concentration, monochloroacetic acid concentration, reaction temperature and time. The optimized product has a yield of 80.47% and a carboxyl group content of 2.8231 mmol•g-1, respectively. The optimum conditions for carboxymethylation are NaOH concentration of 20.0% (wt%), monochloroacetic acid concentration of 37.5% (wt%), temperature of 70 °C and time of 90 min. The optimized CML was characterized by FTIR spectroscopy, 1H NMR spectroscopy and interfacial tension apparatus. The result shows that the substitution reaction of carboxymethylation occurs simultaneously in the phenolic hydroxyl group and aliphatic hydroxyl group in WAL. CML has the surface activity in water for industrial application as dispersant.

The syntheses of 6-C-alkyl derivatives of methyl α-isomaltoside for a study of the mechanism of hydrolysis by amyloglucosidase

2001 ◽  
Vol 79 (2) ◽  
pp. 238-255 ◽  
Author(s):  
Ulrike Spohr ◽  
Nghia Le ◽  
Chang-Chun Ling ◽  
Raymond U Lemieux
Keyword(s):  
Hydrogen Bonds ◽  
Molecular Model ◽  
Aromatic Amino Acids ◽  
Hydroxyl Group ◽  
Bulk Solution ◽  
Anomeric Effect ◽  
Nmr Studies ◽  
Intermolecular Hydrogen Bonds ◽  
Model Calculations ◽  
Derivatives Of

The epimeric (6aR)- and (6aS)-C-alkyl (methyl, ethyl and isopropyl) derivatives of methyl α-isomaltoside (1) were synthesized in order to examine the effects of introducing alkyl groups of increasing bulk on the rate of catalysis for the hydrolysis of the interunit α-glycosidic bond by the enzyme amyloglucosidase, EC 3.2.1.3, commonly termed glucoamylase (AMG). It was previously established that methyl (6aR)-C-methyl α-isomaltoside is hydrolysed about 2 times faster than methyl α-isomaltoside and about 8 times faster than its S-isomer. The kinetics for the hydrolyses of the ethyl and isopropyl analogs were also recently published. As was expected from molecular model calculations, all the R-epimers are good substrates. A rationale is presented for the catalysis based on conventional mechanistic theories that includes the assistance for the decomposition of the activated complex to products by the presence of a hydrogen bond, which connects the 4a-hydroxyl group to the tryptophane and arginine units. It is proposed that activation of the initially formed complex to the transition state is assisted by the energy released as a result of both of the displacement of perturbed water molecules of hydration at the surfaces of both the polyamphiphilic substrate and the combining site and the establishment of intermolecular hydrogen bonds, i.e., micro-thermodynamics. The dissipation of the heat to the bulk solution is impeded by a shell of aromatic amino acids that surround the combining site. Such shields are known to be located around the combining sites of lectins and carbohydrate specific antibodies and are considered necessary to prevent the disruption of the intermolecular hydrogen bonds, which are of key importance for the stability of the complex. These features together with the exquisite stereoelectronic dispositions of the reacting molecules within the combining site offer a rationalization for the catalysis at ambient temperatures and near neutral pH. The syntheses involved the addition of alkyl Grignard reagents to methyl 6-aldehydo-α-D-glucopyranoside. The addition favoured formation of the S-epimers by over 90%. Useful amounts of the active R-isomers were obtained by epimerization of the chiral centers using conventional methods. Glycosylation of the resulting alcohols under conditions for bromide-ion catalysis, provided methyl (6aS)- and (6aR)-C-alkyl-hepta-O-benzyl-α-isomaltosides. Catalytic hydrogenolysis of the benzyl groups afforded the desired disaccharides. 1H NMR studies established the absolute configurations and provided evidence for conformational preferences.Key words: amyloglucosidase (AMG), exo-anomeric effect, 6-C-alkyl-α-D-glucopyranosides and isomaltosides, mechanism of enzyme catalysis.

scholarly journals NMR and X-ray studies of apetalic acid isolated from Calophyllum brasiliense and of its chiral amides

2021 ◽  
Author(s):  
Marie-Rose Van Calsteren ◽  
Ricardo Reyes-Chilpa ◽  
Chistopher K Jankowski ◽  
Fleur Gagnon ◽  
Simón Hernández-Ortega ◽  
...  
Keyword(s):  
Antimycobacterial Activity ◽  
Side Chain ◽  
Carboxyl Group ◽  
X Ray Diffraction ◽  
Rain Forests ◽  
X Ray ◽  
X Ray Crystallography ◽  
Calophyllum Brasiliense ◽  
Derivatives Of

The tropical tree Calophyllum brasiliense (Clusiaceae) grows in the rain forests from Brazil to Mexico. Its leaves, as well as those of other Calophyllum species, are rich sources of chromanone acids, such as apetalic acid, isoapetalic acid, and their derivatives. Apetalic acid has shown significant antimycobacterial activity. The biological activity of apetalic acid has been related to the configuration of three asymmetric centers and the stereochemistry of the molecule; however, the C-19 configuration in the acidic side chain has not been fully resolved. For this reason, the unequivocal determination of the absolute configuration by means of X-ray crystallography in a sample of unique homogeneous apetalic acid stereoisomer was the most important point to start this study. We prepared some chiral amides using the carboxyl group. We determined the C-19 stereochemistry of apetalic acid, and its specific chiral derivatives, using NMR, X-ray diffraction methods, and molecular mechanics. Finally, we observed that steric hindrance in the side chain of apetalic acid leads to restriction of rotation around the pivotal link C-10 and C-19 establishing chiral centers at C2(R), C3(S), and C19(R). We were able to separate derivatives of these two high-rotatory-barrier conformers of apetalic acid by forming diastereoisomeric amides with phenylglycine methyl ester having a chiral center at C-2’. Our results allowed the conclusion of the existence of atropisomerism in the apetalic acid molecule.

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