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Thousands of HarveyFlooded Vehicles Still on Roads

first_img X Listen Share Al Ortiz/Houston Public Media This file photo shows a car stranded near Cypress Creek, north of Houston, on August 29, 2017, during Hurricane Harvey. center_img To embed this piece of audio in your site, please use this code: Vehicle information service Carfax estimates more than 150,000 cars that received flood damage during hurricanes Harvey and Irma are back on American roads.Why is that a problem?Cars that have been flooded can rot from the inside out, Carfax’s Chris Basso said, even long after the flooding occurred.“The water can affect the mechanical systems. It can short out the electrical systems,” he said. “It can even impact the safety systems of the car, like the airbags and the anti-lock brakes, effectively turning these cars into ticking time bombs.”He said if you’re considering a used car for purchase, you should get the vehicle history with the help of its VIN number and have a mechanic inspect it for potential flood damage.Carfax’s research suggests there are nearly half a million flooded cars on American roads overall. 00:00 /00:44last_img read more

A new DielsAlder reaction

first_imgTerminology associated with various cyclizations in the Diels–Alder family of 4π + 2π reactions. a, The classic example of a diene (1,3-butadiene, 1) and a dienophile (ethylene, 2) reacting to give a six-membered cyclic alkene (cyclohexene, 3). b, The absence of four hydrogen atoms gives the tetradehydro (TDDA) variant; the product is in the benzene oxidation state. c, The absence of six hydrogen atoms gives the hexadehydro Diels–Alder (HDDA) variant. d, The unprecedented pentadehydro-Diels–Alder (PDDA) reaction proceeds via an α,3-dehydrotoluene (see 12); importantly, both the HDDA and PDDA reactions result in formation of trappable reactive intermediates. e, α,3-Dehydrotoluenes have previously been generated principally by cyclization of allenyl enynes like 14. Credit: Teng Wang, et al. Nature (2016). DOI: 10.1038/nature17429 Explore further Journal information: Nature Researchers provide evidence for a non-enzymatic pathway to produce paracaseolide A © 2016 Phys.org In the current research Teng Wang, Rajasekhar Reddy Naredla, Severin K. Thompson, and Thomas R. Hoye trap an intermediate formed from the removal of five hydrogens from the typical reactants in a [4+2] Diels-Alder cycloaddition. This intermediate, called α,3-dehydrotoluene, is of interest because its oxidation state is analogous to benzyne, and like benzyne, it can be chemically trapped. This allows for functionalization at unique positions on the molecule. Their work appears in Nature.Removal of hydrogens from the diene of a [4+2] Diels-Alder cycloaddition results in either an allenyne, an unsaturated organic molecule that contains both a double and triple bond, or a diyne, a molecules with two triple bonds. In the case of a tetra-dehydro Diels-Alder reaction, in which four hydrogens are removed, the cycloaddition results in a benzene ring. In the hexa-dehydro Diels Alder reaction (HDDA), a alkyne and a diyne reaction to form a benzyne intermediate, 1, 2-dehydrobenzene. The penta-dehydro Diels Alder reaction (PDDA) involves the reaction of an allenyne an alkyne to produce α,3-dehydrotoluene as an intermediate. The benzyne intermediate from the HDDA reaction and the α,3-dehydrotoluene intermediate from the PDDA reaction are tautomers of each other, and both can be trapped using an appropriate trapping agent. Hoye’s group is the first to trap α,3-dehydrotoluene in a PDDA cyclization reaction. Hoye’s group first suspected that this intermediate occurs from a reaction they did with a particular tetrayne at room temperature in a solution of piperidine. α,3-dehydrotoluene has been observed as a result of Myers-Saito cyclization reaction, but prior to this study, has not been isolated as part of a formal cycloaddition reaction. They found that differences between the intermediates in the HDDA and PDDA reaction has to do with a base-promoted rate-limiting step in the PDDA reaction. Their initial reaction showed that the tetrayne undergoes a piperdine-catalyzed isomerization to produce an allenyne. This then undergoes a PDDA cyclization reaction whose intermediate can be trapped with piperidine, a secondary amine. This mechanism can be generalized to a base-promoted isomerization to produce an allenyne, followed by trapping the intermediate with a protic trapping agent. Hoye’s group looked at other primary and secondary amines as well as oxygen-based nucleophiles such as methanol and water, and found that all of them served as good trapping agents for the α,3-dehydrotoluene intermediate. Hoye’s group also found that the PDDA cyclization reaction worked with a nitrile in place of the alkyne on the allenyne reactant. Furthermore, the PDDA cyclization worked with electron withdrawing groups on the nitrile, and the intermediate can be trapped using the same trapping agents as with the allenyne reaction. Notably, nitriles to do not undergo cyclization in HDDA reactions, therefore, its ability to cyclize in PDDA reactions allows for greater diversity in the types of products that can be made from these reactions.This newly discovered reaction mechanism and isolation of its intermediate allows for the synthesis of several types of organic molecules that would be of interest, including pyridine products. Additionally, it provides insight into the mechanistic differences between the hexa-dehydro Diels Alder reaction and the penta-dehydro Diels Alder reaction, which may be exploited for further studies on cyclization reactions.center_img This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. More information: Teng Wang et al. The pentadehydro-Diels–Alder reaction, Nature (2016). DOI: 10.1038/nature17429AbstractIn the classic Diels–Alder [4 + 2] cycloaddition reaction, the overall degree of unsaturation (or oxidation state) of the 4π (diene) and 2π (dienophile) pairs of reactants dictates the oxidation state of the newly formed six-membered carbocycle. For example, in the classic Diels–Alder reaction, butadiene and ethylene combine to produce cyclohexene. More recent developments include variants in which the number of hydrogen atoms in the reactant pair and in the resulting product is reduced by, for example, four in the tetradehydro-Diels–Alder (TDDA) and by six in the hexadehydro-Diels–Alder (HDDA) reactions. Any oxidation state higher than tetradehydro (that is, lacking more than four hydrogens) leads to the production of a reactive intermediate that is more highly oxidized than benzene. This increases the power of the overall process substantially, because trapping of the reactive intermediate can be used to increase the structural complexity of the final product in a controllable and versatile manner. Here we report an unprecedented overall 4π + 2π cycloaddition reaction that generates a different, highly reactive intermediate known as an α,3-dehydrotoluene. This species is in the same oxidation state as a benzyne. Like benzynes, α,3-dehydrotoluenes can be captured by various trapping agents to produce structurally diverse products that are complementary to those arising from the HDDA process. We call this new cycloisomerization process a pentadehydro-Diels–Alder (PDDA) reaction—a nomenclature chosen for chemical taxonomic reasons rather than mechanistic ones. In addition to alkynes, nitriles (RC≡N), although non-participants in aza-HDDA reactions, readily function as the 2π component in PDDA cyclizations to produce, via trapping of the α,3-(5-aza)dehydrotoluene intermediates, pyridine-containing products. (Phys.org)—The Diels-Alder reaction is a mainstay in organic chemistry. The reaction traditionally involves a diene and a dienophile. The diene has four carbons that are sp2 hybridized to form pi bonds. The dienophile has two sp2 hybridized carbons. The diene and dienophile undergo a cycloaddition reaction to form a cyclohexene. This reaction can be tweaked to make six-membered rings with a higher oxidation state by removing hydrogens from the reactants to make sp hybridized carbons. For example, rather than an alkene and a diene reacting, the reactants could be an alkyne and an allenyne. Citation: A new Diels-Alder reaction (2016, April 27) retrieved 18 August 2019 from https://phys.org/news/2016-04-diels-alder-reaction.htmllast_img read more

Rennesbased research and technology institute B

first_imgRennes-based research and technology institute B<>com and Thomson Video Networks will highlight their ongoing collaboration with the announcement of b<>com’s Ultra Player, a solution for playing the latest generation of uncompressed audio/video content. The b<>com 4K Ultra Player is being sold by Thomson Video Networks as a complement to its ViBE 4K HEVC encoder. Ultra Player is a solution that combines ultra high definition (UHD) images with spatial audio that makes it possible to play immersive content and all videos with very high resolution. Initially developed for b<>com researchers, the tool also completely meets the needs of professionals who want to edit audio/video content prior to compression. Ultra Player’s Web user interface incorporates any workflow, and it works in applications including broadcasting systems, testing laboratories, exhibits, museums and theme parks, universities, and surgical operating theatres, according to the pair.Thomson Video Networks will offer Ultra Player as a bundled solution with the company’s ViBE 4K HEVC encoder for UHD broadcasting.“We work each day to develop innovative solutions that accelerate time to market for content providers looking to offer a higher-quality experience to the end user. The business partnership with Thomson Video Networks is a win-win situation and a perfect example of our willingness to transfer technology to our partners. This new deal will allow both partners to address one of the key issues in the market for new media formats — improving the sensation of being immersed in content,” said Bertrand Guilbaud, CEO of b<>com.“We are already working on upgrades to our Ultra Player; for instance, it will soon be able to play new formats such as UHD HDR at 120 frames per second along with 64 audio tracks. This will make it an essential tool for experimenting with UHD Phase 2, combining immersive video and spatialized audio. Our agreement with Thomson Video Networks is the concrete result of a partnership between the Institute of Research and Technology and an internationally recognised broadcast technology provider, paving the way for b<>com to develop future collaborations with other partners.”Eric Gallier, vice president of marketing at Thomson Video Networks, said, “The experts at b<>com conceive and design technologies that allow content to be published, stored, and shared widely in a constantly changing market. Several of our engineers were involved in the original design of *Ultra Player* within b<>com, so it was only natural that we partner with them for its distribution. This agreement confirms our position at the cutting edge of technologies that are driving the broadcast industry forward, including 4K Phase 2.”Thomson Video Networks will exhibit at IBC on stand 14.A10last_img read more