Modern Views on the Chemistry of Vulcanization Changes. II. Role of Hydrogen Sulfide

1947 ◽  
Vol 20 (2) ◽  
pp. 353-359 ◽  
Author(s):  
Ralph F. Naylor
Keyword(s):  
Hydrogen Sulfide ◽  
Hydrogen Atom ◽  
Ultraviolet Light ◽  
Radical Reaction ◽  
Radical Type ◽  
Polar Reaction ◽  
Reaction Chain ◽  
Free Sulfur

Abstract 1. The normal addition of hydrogen sulfide to olefins is catalyzed by very small proportions of sulfur, but the rate of addition is too slow to provide a satisfactory basis for the hydrogen sulfide-actuated mechanism of vulcanization. 2. The main products of the sulfur-catalyzed (polar) reaction of hydrogen sulfide with polyisoprenes are substituted pentamethylene sulfides, derived by intramolecular normal addition of the initially formed monothiols. 3. The main products of the ultraviolet light-catalyzed (radical) reaction of hydrogen sulfide with polyisoprenes are monothiols and substituted pentamethylene sulfides, the latter derived by intramolecular abnormal addition. 4. The resemblance of the cyclic sulfides obtained by reaction of free sulfur with polyisoprenes to the products of polar hydrogen sulfide addition (as opposed to the products of the radical-type addition) supports the hypothesis that, in the sulfur-olefin reaction, the radical reaction chain is terminated by the capture of a hydrogen atom by an RS* radical, the thiol so formed adding intramolecularly in a polar reaction catalyzed by sulfur.

Role of Hydrogen Disulfide in Vulcanization

1958 ◽  
Vol 31 (2) ◽  
pp. 353-355
Author(s):  
E. I. Tinyakova ◽  
E. K. Khrennikova ◽  
B. A. Dolgoplosk
Keyword(s):  
Hydrogen Sulfide ◽  
Vulcanization Accelerator ◽  
Free Sulfur

Abstract It was shown that the breakdown of hydrogen disulfide in α-olefins results in the exclusive formation of addition products (mono-, di-, and tetrasulfides) without formation of hydrogen sulfide and free sulfur. Similar results were obtained when sulfur reacted with monoethanolamine (vulcanization accelerator) in α-olefin solution.

Nitrogen and Sulfur Transferases

2007 ◽  
Author(s):  
Perry A. Frey ◽  
Adrian D. Hegeman
Keyword(s):  
Steady State ◽  
Reaction Mechanism ◽  
Active Site ◽  
Reaction Mechanisms ◽  
Radical Reaction ◽  
Amino Group ◽  
Steady State Kinetics ◽  
Ping Pong ◽  
Polar Reaction

Unlike other group transfer reactions in biochemistry, the actions of nitrogen transferring enzymes do not follow a single unifying chemical principle. Nitrogen-transferring enzymes catalyze aminotransfer, amidotransfer, and amidinotransfer. An aminotransferase catalyzes the transfer of the NH2 group from a primary amine to a ketone or aldehyde. An amidotransferase catalyzes the transfer of the anide-NH2 group from glutamine to another group. These reactions proceed by polar reaction mechanisms. Aminomutases catalyze 1,2-intramolecular aminotransfer, in which an amino group is inserted into an adjacent C—H bond. The action of lysine 2,3-aminomutase, described in chapter 7, is an example of an aminomutase that functions by a radical reaction mechanism. Tyrosine 2,3-aminomutase also catalyzes the 2,3-amino migration, but it does so by a polar reaction mechanism. In this chapter, we consider NH2-transferring enzymes that function by polar reaction mechanisms. Transaminases or aminotransferases are the most extensively studied pyridoxal-5'-phosphate (PLP)–dependent enzymes, and many aminotransferases catalyze essential steps in catabolic and anabolic metabolism. In the classic transaminase reaction, aspartate aminotransferase (AAT) catalyzes the fully reversible reaction of L-aspartate with α-ketoglutarate according to fig. 13-1 to form oxaloacetate and L-glutamate. Like all aminotransferases, AAT is PLP dependent, and PLP functions in its classic role of providing a reactive carbonyl group to function in facilitating the cleavage of the α-H of aspartate and the departure of the α-amino group of aspartate for transfer to α-ketoglutarate (Snell, 1962). PLP in the holoenzyme functions in essence to stabilize the α-carbanions of L-aspartate or L-glutamate, the major biological role of PLP discussed in chapter 3. The functional groups of the enzyme catalyze steps in the mechanism, such as the 1,3-prototropic shift of the α-proton to C4' of pyridoxamine 5'-phosphate (PMP). The steady-state kinetics corresponds to the ping pong bi bi mechanism shown at the bottom of fig. 13-1. This mechanism allows L-aspartate to react with the internal aldimine, E=PLP in fig. 13-1, to produce an equivalent of oxaloacetate, with conversion of PLP to PMP at the active site (E.PMP), the free, covalently modified enzyme in the ping pong mechanism.

The Role of Reactive Oxygen Species, Kinases, Hydrogen Sulfide, and Nitric Oxide in the Regulation of Autophagy and Their Impact on Ischemia and Reperfusion Injury in the Heart

2020 ◽  
Vol 16 ◽  
Author(s):  
Andrey Krylatov ◽  
Leonid Maslov ◽  
Sergey Y. Tsibulnikov ◽  
Nikita Voronkov ◽  
Alla Boshchenko ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Reactive Oxygen Species ◽  
Hydrogen Sulfide ◽  
Ischemia Reperfusion ◽  
Reactive Oxygen ◽  
Ischemia And Reperfusion ◽  
Oxygen Species ◽  
Ischemia And Reperfusion Injury ◽  
Adaptive Process

: There is considerable evidence in the heart that autophagy in cardiomyocytes is activated by hypoxia/reoxygenation (H/R) or in hearts by ischemia/reperfusion (I/R). Depending upon the experimental model and duration of ischemia, increases in autophagy in this setting maybe beneficial (cardioprotective) or deleterious (exacerbate I/R injury). Aside from the conundrum as to whether or not autophagy is an adaptive process, it is clearly regulated by a number of diverse molecules including reactive oxygen species (ROS), various kinases, hydrogen sulfide (H2S) and nitric oxide (NO). The purpose this review is to address briefly the controversy regarding the role of autophagy in this setting and to examine a variety of disparate molecules that are involved in its regulation.

Taurine treatment reverses protein malnutrition-induced endothelial dysfunction of the pancreatic vasculature: the role of hydrogen sulfide

Metabolism ◽  
2021 ◽  
pp. 154701
Author(s):  
Daniele M. Guizoni ◽  
Israelle N. Freitas ◽  
Jamaira A. Victorio ◽  
Isabela R. Possebom ◽  
Thiago R. Araujo ◽  
...  
Keyword(s):  
Hydrogen Sulfide ◽  
Endothelial Dysfunction ◽  
Protein Malnutrition ◽  
Taurine Treatment

Crystal Violet, an Electronic Model Substance for Rubber and Related Olefins

1951 ◽  
Vol 24 (1) ◽  
pp. 169-181 ◽  
Author(s):  
G. J. van Veersen
Keyword(s):  
Crystal Violet ◽  
Electronic Structures ◽  
Radical Reaction ◽  
Test Tube ◽  
Chemical Agent ◽  
Blue Color ◽  
Electronic Model ◽  
Model Substance ◽  
Model Substances ◽  
Polar Reaction

Abstract It is shown that triphenylmethyl dyes like crystal violet can be used as model substances for rubber and related olefins. Arguments are given in support of the assumption that agents which react with rubber and related olefins in a polar manner cause a reversible shift in color from blue to yellow with crystal violet, whereas a fading of the blue color of crystal violet (if alkaline or reducing agents are excluded) points to a radical reaction. Since the electronic structures of donor olefins and crystal violet are considered and not the molecular structure, as usually is done in the choice of a model substance, these dyes have been named electronic model substances. Though crystal violet, as an electronic model substance cannot be used for the study of the overall reactions, information can often be obtained concerning the first step in a reaction of rubber with a certain chemical agent by means of a simple test-tube reaction with crystal violet. It was pointed out that the π-electron availability at the non-methylated carbon atom of the double bond in rubber and at the nitrogen atoms in crystal violet is probably of the same order. As an application of crystal violet as an electronic model substance for rubber, a polar reaction between sulfur and rubber is suggested as the first step in vulcanization.

Role of hydrogen sulfide in cerebrovascular alteration during aging

2019 ◽  
Vol 42 (5) ◽  
pp. 446-454 ◽  
Author(s):  
Juyeon Mun ◽  
Hye-Min Kang ◽  
Junyang Jung ◽  
Chan Park
Keyword(s):  
Hydrogen Sulfide

NaHS inhibits NF-κB signal against inflammation and oxidative stress in post-infectious irritable bowel syndrome

RSC Advances ◽  
2016 ◽  
Vol 6 (69) ◽  
pp. 64208-64214 ◽  
Author(s):  
Shenglan Yang ◽  
Danfang Deng ◽  
Yingying Luo ◽  
Yanran Wu ◽  
Rui Zhu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Irritable Bowel Syndrome ◽  
Hydrogen Sulfide ◽  
Murine Model ◽  
Irritable Bowel ◽  
And Oxidative Stress ◽  
Post Infectious

In this study, the alleviating role of hydrogen sulfide (H2S) was investigated in a Post-Infectious Irritable Bowel Syndrome (PI-IBS) murine model and Caco-2 cells.

scholarly journals Role of molybdenum in corrosion of iron-based alloys in contact with hydrogen sulfide containing solution

2016 ◽  
Vol 68 (6) ◽  
pp. 595-603 ◽  
Author(s):  
G. Genchev ◽  
C. Bosch ◽  
E. Wanzenberg ◽  
A. Erbe
Keyword(s):  
Hydrogen Sulfide ◽  
Iron Based ◽  
Corrosion Of Iron
Sign in / Sign up

Export Citation Format

Share Document