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What is a good way to synthesize unsymmetrical ureas?

Phosgene reacts with carboxylic acids to give anhydrides, with liberation of carbon dioxide. This has been used to activate acids to attack from nucleophiles, e.g.

In contrast, reaction with acids in the presence of a variety of catalysts (including , , and ) cleanly affords the corresponding acid chloride. has also been used as a catalyst (eq 2).Phosgene reacts with alcohols to give chloroformates,, and with secondary amines to give chloroformamides (it reacts preferentially with the latter). The formation of a chloroformate is the first step in the Barton oxidation of primary alcohols to aldehydes, which is followed by complex formation with and elimination by base (eq 3), a mechanism closely related to that of the Swern and Moffatt oxidations.There are many examples of further displacement of the chloroformate in an intramolecular or intermolecular sense by suitably disposed second nucleophiles (e.g.

DDT was first synthesized in 1874 by a young German chemistry student, Othmar Zeidler.

What is a good way to synthesize unsymmetrical ureas

The sulfur mustards, of which mustard gas is a member, are a class of related , vesicant with the ability to form large blisters on exposed skin. In their pure form most sulfur mustards are colorless, odorless, viscous liquids at room temperature. When used as they are usually yellow-brown in color and have an odor resembling mustard plants, garlic or horseradish, which is how they got their name. However, these compounds have absolutely no relation whatsoever to culinary mustard.

Sulfur mustards are variations of mustard gas (bis-(2-chloroethyl) sulfide), which was first synthesized by in 1860, though it is possible that it was developed as early as 1822 by M. Depretz. In 1886 V. Meyer published a paper describing a synthesis which produced good yields. Mustard gas is referred to by numerous other names, including HD, senfgas, sulfur mustard, blister gas, s-lost, lost, Kampfstoff LOST, yellow cross liquid, and yperite. The abbreviation LOST comes from the names Lommel and Steinkopf, who developed a process for mass producing the gas for war use at the German company . This involved reacting thiodiglycol with .

Mustard agents, including sulfur mustard, are regulated under the 1993 . Three classes of chemicals are monitored under this convention, with and mustard grouped in the highest risk class, "schedule 1".

Phosgene still is used to create numerous products including plastics, pharmaceutical agents, polyurethanes, dyes, and . Industries in the United States alone use over 1 billion pounds of phosgene yearly ().

It has also been used extensively as a most notably in World War I.

The great majority of phosgene is used in the ..

Phosgene was first used as a in World War I by the Germans, but was later used by the French, Americans, and British in that same conflict (). Initial deployment of the gas was by the Germans at on , 1915 when they released around 4000 cylinders of phosgene combined with against the British. Phosgene has rarely been used since World War I, partly because most countries frowned upon the use of chemical weapons and partly because newer agents were developed (). Phosgene was responsible for the majority of deaths that result from ().

Hence, available VLE data of relevant carbonate systems has been taken from literature to fit corresponding UNIFAC parameters which have subsequently been used for the description of the relevant chemical equilibria and reaction kinetics.

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The great majority of phosgene is used in the production of ..

Industry widely uses phosgene for the synthesis of isocyanates, ..

Phosgene-derived chloroformates and acid chlorides are, by their nature, reactive chemical species and are employed as key building blocks in many diverse downstream applications. These intermediates are used in the manufacture of organic peroxide initiators for use in plastics and in activating groups used to make antibiotics and other pharmaceuticals.

Phosgene is the chemical compound with the formula COCl 2

The research group headed by Prof. Deng Youquan of the R&D Center for Green Chemistry and Catalysis of the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, (LICP, CAS) has achieved the heterogeneous catalyzed non-phosgene synthesis of N-substituted carbamates, an important isocyanate precursor.

Here Are The Four Main Poison Gases Used In World War I

However, the Vilsmeier reagent generated from phosgene is claimed to be a more efficient reagent for the dehydration of primary amides to nitriles.Tertiary amides (and thioamides) with an -proton react instead to give chloro enamines. These can undergo nucleophilic substitution (eq 15)., Chloro enamines are also intermediates in synthetically useful dehydrogenation reactions, using or DMSO as oxidant (eq 16). Tertiary ureas and thioureas form related adducts which have been utilized in the synthesis of hindered guanidine bases by further reaction with amines (eq 17).In recent years, (triphosgene) has been introduced as a crystalline phosgene source; similarly, (diphosgene) has been used as a liquid equivalent (bp 128 °C, 1.65 g mL-1).

Carboxylic acid - Synthesis of carboxylic acids | …

Researchers have developed a nickel-promoted magnetic iron oxide catalyst for the effective syntheses of N-substituted carbamates. The catalyst could be easily isolated using external magnetic field and recovered for several runs without deactivation. In general, good to excellent yields were obtained with various amines and alkyl carbamates. Catalyst characterization results suggested the catalytic activity may be derived from the delicate synergy between Ni and Fe species resulted in specific basic sites. Reaction pathway investigations revealed that the N-substituted carbamates were formed via substitute urea intermediate and the catalyst mainly promoted the further alcoholysis of the urea intermediate. The technology provided a cheap, safe and environmental-benign non-phosgene route for the N-substituted carbamates synthesis.

Synthesis of urea derivatives - Organic Chemistry Portal

Isocyanates are major raw materials for the manufacture of polyurethane, which have been widely used in producing elastomer, elastic fiber, coatings, and so on. They mainly include hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenyl-methane-diisocyanate (MDI) and isophorone diisocyanate (IPDI). Currently, isocyanates are produced on a commercial scale using extremely toxic phosgene as the carbonyl source, which leads to serious equipment corrosion, phosgene leakage, environmental pollution and even personnel death. Thus, there have been increasing interests in developing green alternative methods for isocyanate production. The existing non-phosgene approaches mainly involve reductive carbonylation of nitro-compound, oxidative carbonylation of amine compounds and aminolysis reaction of dimethyl carbonate. These methods avoid using phosgene, however, they have many problems, such as the toxicity of CO, the explosion of CO and O2 under high temperature, high cost of dimethyl carbonate and difficult separation from the methanol. Theoretically, CO2 should be the ideal carbonyl source in carbonylation reactions. Unfortunately, the high chemical inertness of CO2 limits its practical use in carbonylation processes.


This useful reaction constitutes a general method for isocyanate synthesis (eq 7).With tertiary amines, phosgene-amine complexes can be formed. Warming results in decomposition to an -dialkylchloroformamide by elimination of alkyl chloride. This has been utilized for the mild and high yielding deprotection of -methyl amines (eq 8). -Chloroethyl chloroformate, prepared from phosgene and , has also been used for this purpose.The action of phosgene on amides (and thioamides) initially gives dehydration to a chloromethyleneiminium chloride (eq 9).

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