Tetramethylurea
Chemical compound
From Wikipedia, the free encyclopedia
Tetramethylurea (TMU) is the organic compound with the formula (Me2N)2CO. It is a substituted urea. This colorless liquid is used as an aprotic-polar solvent, especially for aromatic compounds and is used e. g. for Grignard reagents.[1] TMU has a mild aromatic odor and, unlike other compounds of urea, is a colorless liquid.[2]
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| Names | |
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| Preferred IUPAC name
Tetramethylurea | |
| Other names
1,1,3,3-Tetramethylurea | |
| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.010.159 |
| EC Number |
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PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| C5H12N2O | |
| Molar mass | 116.164 g·mol−1 |
| Appearance | Colorless liquid |
| Density | 0.968 g/mL |
| Melting point | −1.2 °C (29.8 °F; 271.9 K) |
| Boiling point | 176.5 °C (349.7 °F; 449.6 K) |
| Hazards | |
| GHS labelling: | |
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| Danger | |
| H302, H360, H361 | |
| P201, P202, P264, P270, P281, P301+P312, P308+P313, P330, P405, P501 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Production
TMU is obtained by the reaction of dimethylamine with phosgene in aqueous sodium hydroxide in a 2:1 ratio.[3] A similar method combines dimethylcarbamoyl chloride with excess dimethylamine.[4][5] This reaction is highly exothermic. The removal of the resulting dimethylamine hydrochloride requires some effort.[1]
The reaction of diphenylcarbonate with dimethylamine in an autoclave is also effective.
TMU is formed upon the oxygenation of tetrakis(dimethylamino)ethylene (TDAE).[6]
TMU is also a common by-product formed in amide bond forming reactions and peptide synthesis with uronium and guanidinium-based reagents including HATU, HBTU, and TCFH.
Applications
TMU is miscible with a variety of organic compounds, including acids (e.g. acetic acid), bases (e.g. pyridine), and organic substances (e.g. ε-caprolactam, benzoic acid). TMU can also dissolve some inorganic salts such as silver nitrate and sodium iodide.[7][8] TMU is often used in place of hexamethylphosphoramide (HMPA), which is a suspected carcinogen.[9]
TMU is suitable as a reaction medium for the polymerization of aromatic diacid chlorides (such as isophthalic acid) and aromatic diamines (such as 1,3-diaminobenzene (m-phenylenediamine)) to aramids such as poly (m-phenylene isophthalamide) (Nomex)[10][11]
The polymerization of 4-amino benzoic acid chloride hydrochloride in TMU provides isotropic viscous solutions of poly(p-benzamide) (PPB), which can be directly spun into fibers.[12]
In a TMU-LiCl mixture, stable isotropic solutions can be obtained up to a PPB polymer concentration of 14%.[13]
TMU also dissolves cellulose ester and swells other polymers such as polycarbonates, polyvinyl chloride, or aliphatic polyamides - usually at elevated temperature.[1]
Strong and hindered non-nucleophilic guanidine bases are accessible from TMU in a simple manner,[14][15] which are in contrast to the fused amidine bases DBN or DBU not alkylated.
A modification of the Koenigs-Knorr reaction for building glycosides from 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide (acetobromoglucose) originates from S. Hanessian who used the silver salt silver trifluoromethanesulfonate (TfOAg) and as a proton acceptor tetramethylurea.[16] This process variant is characterized by a simplified process control, high anomeric purity and high yields of the products. If the reaction is carried out with acetobromoglucose and silver triflate/tetramethylurea at room temperature, then tetramethylurea reacts not only as a base, but also with the glycosyl to form a good isolable uroniumtriflates in 56% yield.[17]
Safety
The acute toxicity of TMU is moderate. However, it is embryotoxic and teratogenic towards several animal species.[18] TMU has been demonstrated to exhibit dermal and eye irritation.[19] The sensitization potential of TMU was shown to be low compared (non-sensitizing at 1% in LLNA testing according to OECD 429[20]).