• Non-isocyanate polyurethane (NIPU) foams from a commercial hydrolysable tannin extract, chestnut wood tannin extract, have been prepared to determine what chemical species and products are taking part in the reactions involved. (techscience.com)
  • RNH2 + CO2}}} This reaction is exploited in tandem with the production of polyurethane to give polyurethane foams. (wikipedia.org)
  • Both are based on a two-component system , and the curing mechanisms is by co-reaction, where isocyanate is a common component, and the second component is a polyether polyamine for polyureas, while polyether polyol is for polyurethane (see Figure 1). (corrosionpedia.com)
  • Polyurea and polyurethane reactions. (corrosionpedia.com)
  • The polyurethane reaction is sensitive to low temperatures and moisture due to the addition of catalysts. (corrosionpedia.com)
  • The polyurethane system is susceptible to blistering when the humidity is greater than 5% , due to the competition between hydroxyl-polyol and water for the reaction with an isocyanate group. (corrosionpedia.com)
  • Polyurethane foam is a porous, cellular-structured, synthetic material made from the reaction of polyols and diisocyanates. (iqsdirectory.com)
  • The first polyurethane was formed by the reaction between a diamine-forming polyurea and an aliphatic diisocyanate. (iqsdirectory.com)
  • In this one-step process, polyurethane was formed by the reaction of the isocyanates with the hydroxyl-functional groups from the polyester, while its gas phase was formed by the generation of carbon dioxide. (iqsdirectory.com)
  • Further refining of blowing agents, polyether polyols, and polymeric isocyanates led to the advancement from flexible polyurethane foams to rigid polyurethane foams. (iqsdirectory.com)
  • There are a number of health concerns associated with memory foam, primarily due to the isocyanate chemicals in polyurethane. (savvyrest.com)
  • Two industrially important chemicals where CO 2 utilization can have a significant impact on sustainability are the production of aromatic carbamates, which may be potential precursors of isocyanates for the polyurethane industry, and the production of dimethylcarbonate (DMC). (sintef.no)
  • Cleaners for Cured PU Foam, Cured Polyurethane Foam, PU Foam Remover, Cured PU and Isocyanate Foam Cleaner, Isocyanates Remover. (tedgar.net)
  • In addition to introducing thiourethane dynamic chemistry as a simple way to achieve high-value recyclability of polyurethane-type networks by reprocessing and/or monomer recovery, our study shows that tuning of the reaction stoichiometry may be a facile approach to optimize property recovery after reprocessing for some dynamic networks that exhibit property loss when at stoichiometric balance. (northwestern.edu)
  • Isocyanates have been a leading chemical cause of occupational asthma since their utility for generating polyurethane was first recognized over 60 years ago, yet the mechanisms of isocyanate asthma pathogenesis remain unclear. (cdc.gov)
  • Persons exposed only to methyl isocyanate gas pose no risk of secondary contamination. (cdc.gov)
  • The new results from ALMA show that methyl isocyanate gas surrounds each of these young stars. (eurekalert.org)
  • Polyurethanes can be synthesized during the polyaddition reaction by using suitable catalyst systems to increase the reaction time of the components. (corrosionpedia.com)
  • In phenyl isocyanate, the C=N and C=O distances are respectively 1.195 and 1.173 Å. (wikipedia.org)
  • In the industrial synthesis of 4,4'-methylene diphenyl diisocyanate (MDI), an unwanted side reaction between the product and the starting material, 4,4'-methylene dianiline, can lead to the formation of ureas. (gla.ac.uk)
  • In terms of bonding, isocyanates are closely related to carbon dioxide (CO2) and carbodiimides (C(NR)2). (wikipedia.org)
  • 1-Methyl-phospholene-1-oxide is used as a catalyst in the production of carbodiimides from isocyanates. (clariant.com)
  • Reducing carbodiimides (RN=C=NR) and isocyanates (RN=C=O) is an appealing route to formamidine and formamide functional groups, which appear, for example, in biologically active compounds. (chemistryviews.org)
  • Using this catalyst, the team performed hydroboration reactions of seven carbodiimides and nine isocyanates with pinacolborane at room temperature. (chemistryviews.org)
  • The carbohydrate skeleton of the hydrolysable tannin is also able to participate through its hydroxyl groups to the same two reactions rendering the whole molecular complex able to react to form NIPUs. (techscience.com)
  • C6H11N)2C + CO2}}} Isocyanates also can react with themselves. (wikipedia.org)
  • In each case, the isocyanates react preferentially with the N-terminus of the peptide. (cdc.gov)
  • Due to the highly reactive thiol end-groups, polysulfide polymers react under the influence of oxidizing agents, epoxies, isocyanates or acrylates by forming highly elastic and rubber-like high-molecular-weight macromolecules without significant physical shrinking. (adhesivesmag.com)
  • Methyl isocyanate is readily absorbed through the upper respiratory tract. (cdc.gov)
  • Acute exposure to methyl isocyanate vapors below the odor threshold can be irritating to the eye and respiratory epithelium. (cdc.gov)
  • Animal studies have suggested that skin exposure to isocyanates may be an important risk factor for respiratory sensitization leading to asthma. (cdc.gov)
  • The present study provides in vivo evidence that a GSH mediated pathway underlies asthma-like eosinophilic inflammatory responses to respiratory tract isocyanate exposure. (cdc.gov)
  • The HCP who developed acute respiratory illnesses (ARI) (1 of acute cough, runny nose, body aches, or feverishness) were tested for influenza using reverse-transcription polymerase chain reaction (rt-PCR). (cdc.gov)
  • Owing to the hazardous nature of phosgene, the production of isocyanates requires special precautions. (wikipedia.org)
  • Methyl isocyanate is made by reacting methylamine with phosgene. (cdc.gov)
  • It has been postulated these ureas undergo further reaction with phosgene to produce a precursor to chlorine radicals, which could then attack the MDI backbone forming conjugated systems that would promote colour in the final products. (gla.ac.uk)
  • Novel nano-cellulose based nano-structures modified with hyper-branched polymers were prepared by using isocyanate linking chemistry. (4spe.org)
  • Methods Three auto body shops of different size which use different paint systems were examined for the presence of aliphatic isocyanates on environmental surfaces and workers' skin and for breakthrough of personal protective equipment. (cdc.gov)
  • Using model compounds, we demonstrated the dual nature of the mechanism associated with catalyzed thiourethane dynamic chemistry: At elevated temperature, thiourethane groups undergo exchange reactions with free thiol groups and thermal reversion to thiols and isocyanates. (northwestern.edu)
  • Throughout the project side reactions involving the formation of carbodiimide from CCC and a secondary route for the phosgenation of the urea to the isocyanate have been investigated and are presented within a global reaction scheme. (gla.ac.uk)
  • It also catalyses phosgenation reactions. (clariant.com)
  • It was also found the ureas were only partially soluble in the process solvent leading to research into the structure of three different urea molecules and the proposal of a modified reaction scheme. (gla.ac.uk)
  • Structural elucidation of isocyanate-peptide adducts using tandem mass spectrometry. (cdc.gov)
  • Worachartcheewan, Apilak Abstract: Pyrrolidines type 2,4-disubstituted (alkyl, aryl or heteroaryl)-6,8-dioxo-3,7-diazabicyclo [3.3.0] octanes (8a-d) were successfully synthesized by an efficient one pot 1,3-dipolar cycloaddition of azomethine ylides (in situ generated from the reaction of aromatic aldehydes and methyl ester of alpha-amino acids) with dipolarophile (N-phenylmaleimide). (tu-dortmund.de)
  • Tp* 2 U(NBn), Tp* 2 U(N p -Tol), and Tp* 2 U(Ndetp), along with previously reported Tp* 2 U(NPh) and Tp* 2 U(NAd) (Ad = 1-adamantyl), readily undergo [2π+2π] cycloaddition with isocyanates and isothiocyanates to generate κ 2 -ureato and κ 2 -thioureato derivatives, respectively. (acs.org)
  • This method is based on two main steps: the reaction with dimethyl carbonate and the formation of urethane bonds by further reaction of the carbonated tannin with a diamine-like hexamethylene diamine. (techscience.com)
  • Hypersensitivity pneumonitis is a type of inflammation in and around the tiny air sacs (alveoli) and smallest airways (bronchioles) of the lung caused by a hypersensitivity reaction to inhaled organic dusts or, less commonly, chemicals. (msdmanuals.com)
  • Organic dusts that contain microorganisms or proteins, and chemicals, such as isocyanates, may cause hypersensitivity pneumonitis. (msdmanuals.com)
  • Persons whose skin or clothing is contaminated with liquid methyl isocyanate can secondarily contaminate rescuers by direct contact or through offgassing of vapor. (cdc.gov)
  • I suspect his symptoms are due to toluene diisocyanate or a similar isocyanate vapor. (cdc.gov)
  • Addition of multiple isocyanates to the peptide occurs via polymerization of the isocyanate at the N-terminus, rather than via addition of multiple isocyanate molecules to varied residues within the peptide. (cdc.gov)
  • In this area, we have developed a methodology for the incorporation of protected isocyanates into organic molecules and this chemistry is being applied to the synthesis of a diverse set of biologically important, nitrogen-containing heterocycles. (exeter.ac.uk)
  • In particular, we have developed methods for the stereoselective incorporation of the 1,2,4-dithiazolidine-3,5-dione (Dts imide) moiety into molecules as a masked isocyanate equivalent. (exeter.ac.uk)
  • Toxicity aside, memory foam can be a comforting surface with a contouring reaction that provides good pressure relief initially. (savvyrest.com)
  • Examples of compounds that may cause sensitization in some individuals are diazomethane, various isocyanates, formaldehyde, and benzylic and allylic halides. (unr.edu)
  • Those of highest concern include halogenated flame retardants, formaldehyde-based binders, and isocyanates reacting on site. (healthybuilding.net)
  • Isocyanates are common intermediates in the synthesis of primary amines via hydrolysis: Hofmann rearrangement, a reaction in which a primary amide is treated with a strong oxidizer such as sodium hypobromite or lead tetraacetate to form an isocyanate intermediate. (wikipedia.org)
  • Whilst much has been written about this reaction, relatively little characterisation has been carried out on the reaction intermediates. (exeter.ac.uk)
  • Addition of in situ generated Schwartz reagent to widely available isocyanates enables a chemoselective, high-yielding, and versatile synthesis of variously functionalized formamides. (organic-chemistry.org)
  • Isocyanates are electrophiles, and as such they are reactive toward a variety of nucleophiles including alcohols, amines, and even water having a higher reactivity compared to structurally analogous isothiocyanates. (wikipedia.org)
  • In organic chemistry, isocyanate is the functional group with the formula R−N=C=O. Organic compounds that contain an isocyanate group are referred to as isocyanates. (wikipedia.org)
  • Polythiourethane (PTU) can be synthesized by a type of click chemistry involving the reaction of thiols with isocyanates. (northwestern.edu)
  • Test: Reaction Mechanism Level - 5 for Chemistry 2023 is part of Organic Chemistry preparation. (edurev.in)
  • The Test: Reaction Mechanism Level - 5 questions and answers have been prepared according to the Chemistry exam syllabus.The Test: Reaction Mechanism Level - 5 MCQs are made for Chemistry 2023 Exam. (edurev.in)
  • Solutions of Test: Reaction Mechanism Level - 5 questions in English are available as part of our Organic Chemistry for Chemistry & Test: Reaction Mechanism Level - 5 solutions in Hindi for Organic Chemistry course. (edurev.in)
  • Inhalation is the major route of exposure to methyl isocyanate. (cdc.gov)
  • Significant exposure to methyl isocyanate vapors would most likely be the result of accidental release of methyl isocyanate to the air such as occurred in Bhopal, India in 1984, where the primary effect was pulmonary edema with some alveolar wall destruction. (cdc.gov)
  • Significant dermal exposure to methyl isocyanate would not likely occur outside an occupational environment in which methyl isocyanate is stored or used. (cdc.gov)
  • Once sensitization to a chemical occurs, subsequent exposure to extremely low doses of the chemical produces an allergic reaction (for example, skin rash or asthma). (unr.edu)
  • Background Little is known about the extent of human isocyanate skin exposure in auto body shops and the effectiveness of personal protective equipment. (cdc.gov)
  • Conclusions Contaminated environmental surfaces and skin exposure to isocyanates were documented in several auto body shops. (cdc.gov)
  • 1989]. However, exposure isocyanates were not available until recently when calori- characterization in auto body workers, particularly painters, metric sampling pads were developed. (cdc.gov)
  • The mechanisms by which isocyanates cause asthma remain unclear, hampering disease prevention, diagnosis, and treatment.7 It is assumed the reactive nature of N=C=O groups underlies isocyanate asthma, with a hapten-based mechanism as the most obvious pathway to pathogenesis.8 However, the critical "self" reaction targets for isocyanate in vivo remain uncertain. (cdc.gov)
  • Isocyanates should not be confused with cyanate esters and isocyanides, very different families of compounds. (wikipedia.org)
  • The reaction of compounds 8a-d with hydrazine in ethanol at room temperature took place under nucleophilic substitution which furnished 5-amino-4,6-dioxo-octahydropyrrolo [3,4-b] pyrrole-3-carboxylic acid phenylamides (12a-d). (tu-dortmund.de)
  • O. Maduka Ogba, Allegra L. Liberman-Martin, Chapman University, Orange, CA, USA, and colleagues have developed a method for the selective hydroboration of carbodiimide and isocyanate substrates (pictured above) using Lewis-basic carbon catalysts. (chemistryviews.org)
  • According to the team, the work represents the first report of carbodiimide or isocyanate reduction catalyzed by a neutral, Lewis-basic organocatalyst. (chemistryviews.org)
  • May produce an allergic reaction. (diy.com)
  • The choice of catalyst controls the selectivity of the targeted isocyanate reactions. (corrosionpedia.com)
  • The hydroxyl groups on the tannin polyphenols and on the carbohydrates intimately linked with it and part of a hydrolysable tannin are the groups involved in these reactions. (techscience.com)
  • It is also possible to make so-called hybrid systems, in which the isocyanate is reacted with a mixture of hydroxyl and amino groups. (corrosionpedia.com)
  • The importance of the Bergmann cyclisation reaction in the mode of action of anti-tumour enediyne antibiotics such as calicheamicin- alpha and the neocarzinostatins provided the starting point for this collaborative project for which Dr David Smith is the principal investigator. (exeter.ac.uk)
  • Dusts that contain microorganisms or proteins may cause a hypersensitivity reaction in the lungs. (msdmanuals.com)
  • [ 2 ] According to Huber et al, the presence of corrosion products and a hypersensitivity reaction in patients suggests that there is a relation between corrosion and implant-related hypersensitivity. (medscape.com)
  • At temperatures below 39ºC (102ºF), methyl isocyanate is a very flammable colorless liquid that readily evaporates when exposed to air. (cdc.gov)
  • Methyl isocyanate is handled and transported as a very flammable and explosive liquid. (cdc.gov)
  • An organic compound with two isocyanate groups is known as a diisocyanate. (wikipedia.org)
  • Foam insulations commonly contain toxic flame retardants, and spray foam contains asthma -causing isocyanates. (healthybuilding.net)
  • Agents encountered by workers can also cause allergic problems such as asthma, nasal and sinus allergies, hives, and even severe anaphylactic reactions. (cdc.gov)
  • 1990]. A number of studies have described cases of However, little has been reported in the literature on surface asthma in auto body spray painters [Cockcroft and Mink, and skin contamination by isocyanates in auto body shops. (cdc.gov)
  • Direct contact with liquid or concentrated vapors of methyl isocyanate may cause irritation of the skin or eyes and severe ocular damage. (cdc.gov)
  • Although unlikely, ingestion of liquid methyl isocyanate could produce severe gastrointestinal irritation. (cdc.gov)
  • Curtius rearrangement degradation of an acyl azide to an isocyanate and nitrogen gas. (wikipedia.org)
  • Methyl isocyanate contains carbon, hydrogen, nitrogen and oxygen atoms in the chemical configuration CH3NCO. (eurekalert.org)
  • The cyanate (cyanate ester) functional group (R−O−C≡N) is arranged differently from the isocyanate group (R−N=C=O). Isocyanides have the connectivity R−N≡C, lacking the oxygen of the cyanate groups. (wikipedia.org)
  • The direct observation of isocyanate binding to the N-terminus of peptides under these experimental conditions is in good agreement with previous studies on the relative reaction rate of isocyanate with amino acid functional groups. (cdc.gov)
  • Qualitative detection of contamination by isocyanates was conducted using a wipe-sampling technique. (cdc.gov)
  • The analysis by Matrix-Assisted Laser Desorption Ionization (MALDI-TOF) mass spectrometry and 13 C Nuclear Magnetic Resonance ( 13 C NMR) to further investigate the reaction mechanisms involved revealed the unsuspected complexity of chestnut hydrolysable tannin, with different fragments reacting in different manners forming a hardened network of considerable complexity. (techscience.com)
  • However, the presence of multiple polar double bonds in these heterocumulene-type substrates can make selective reduction reactions challenging to achieve. (chemistryviews.org)
  • Children exposed to the same levels of methyl isocyanate as adults may receive larger doses because they have relatively greater lung surface area:body weight ratios and higher minute volume:weight ratios. (cdc.gov)
  • To better understand the chemical species produced when isocyanates are reacted with model peptides, tandem mass spectrometry was employed to unambiguously identify the binding site of four commercially-relevant isocyanates on model peptides. (cdc.gov)
  • Carbon is a product of the reaction of diisocyanates with water. (iqsdirectory.com)
  • image: ALMA has observed stars like the Sun at a very early stage in their formation and found traces of methyl isocyanate -- a chemical building block of life. (eurekalert.org)
  • Two teams of astronomers have harnessed the power of the Atacama Large Millimeter/submillimeter Array ( ALMA ) in Chile to detect the prebiotic complex organic molecule methyl isocyanate [1] in the multiple star system IRAS 16293-2422. (eurekalert.org)
  • Results Environmental surfaces such as painters' workbenches, spray equipment, and cleaning tools were found contaminated with isocyanates. (cdc.gov)
  • Significant exposures to methyl isocyanate occur primarily in occupational settings. (cdc.gov)
  • Odors of methyl isocyanate may not provide adequate warning of hazardous concentrations because the Immediately Dangerous to Life or Health (IDLH) limit is only 3 ppm and the threshold for detection of methyl isocyanate vapors ranges from 2 to 5 ppm in humans. (cdc.gov)
  • Health(IDLH) limit is only 3 ppm and the threshold for detection of methyl isocyanate vapors ranges from 2 to 5 ppm in humans. (cdc.gov)
  • Supporting Information: LC-MS characterization of GSH-MDI reaction products, Tables of peptides matched to albumin or modified albumin, and MS/MS data on the GSH-MDI modified albumin peptide containing residues 411-428. (cdc.gov)
  • Each team identified and isolated the signatures of the complex organic molecule methyl isocyanate [4]. (eurekalert.org)
  • Isocyanates, both MDI and TDI are widely used in as spraying applications of insulation due to the speed and flexibility of applications. (wikipedia.org)
  • Latex gloves were not adequate protection for workers using isocyanate paints. (cdc.gov)
  • Lossen rearrangement, the conversion of a hydroxamic acid to an isocyanate via the formation of an O-acyl, sulfonyl, or phosphoryl intermediate. (wikipedia.org)
  • No evidence of side-chain/ isocyanate adduct formation exclusive of the N-terminus was observed. (cdc.gov)
  • This image shows the spectacular region of star formation where methyl isocyanate was found. (eurekalert.org)
  • The mechanism for this reaction is based on the formation of a sulfur ylide-like intermediate. (beilstein-journals.org)
  • In addition, they may be exposed to higher levels than adults in the same location because of their short stature and the higher levels of methyl isocyanate found nearer to the ground. (cdc.gov)
  • Following the discovery of sugars, we've now found methyl isocyanate. (eurekalert.org)
  • A small level (10 mol %) of excess thiol groups reduces reversion, thereby suppressing undesired side reactions during reprocessing and promoting thiol-thiourethane exchange reactions, leading to excellent property recovery after multiple recycling steps. (northwestern.edu)