Toluene diisocyanate
Encyclopedia : T : TO : TOL : Toluene diisocyanate
| Toluene-2,4-diisocyanate | |
|---|---|
|
| |
| General | |
| Systematic name | 2,4-Diisocyanatotoluene |
| Molecular formula | C9H6N2O2 |
| SMILES | ? |
| Molar mass | 174.2 g/mol |
| Appearance | colorless liquid or solid |
| CAS number | [584-84-9] |
| Properties | |
| Density and phase | 1.2 g/cm3, solid |
| Solubility in water | Reacts |
| Melting point | 22 °C |
| Boiling point | 251 °C |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Very toxic (T+) Carc. Cat. 3 |
| NFPA 704 | |
| R-phrases | R26, R36/37/38, R40, R42/43, R52/53 |
| S-phrases | S1/2, S23, S36/37, S45, S61 |
| Flash point | 127 °C |
| RTECS number | CZ6300000 |
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Related isocyanates | Methylene diphenyl diisocyanate |
| Related compounds | Polyurethane |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) [Chemical infoboxInfobox disclaimer and references] | |
Toluene diisocyanate (TDI) is an aromatic diisocyanate. It is produced for reaction with polyols to form polyurethanes. It is a highly produced diisocyanate, accounting for 34.1 % of the global isocyanate market in 2000, second only to MDI.[#endnote_TPB-1]
Numbering of the ring atoms shown with blue numbers
Synthesis
There are six steps to the synthesis of pure 2,4-TDI:[#endnote_TPB-2]- Nitration: Reaction of toluene with nitric acid and a catalyst to form dinitrotoluene
- Hydrogenation: Reaction of the dinitrotoluene with hydrogen and a catalyst to form a mixture of isomers of toluene diamine (TDA)
- Purification: Distillation of the TDA mixture to produce meta-TDA
- Phosgenation: Reaction of the meta-TDA with phosgene to form a crude TDI mixture
- Purification: Distillation of the crude TDI mixture to produce an 80:20 mixture of 2,4-TDI and 2,6-TDI, known as TDI (80/20)
- Differentiation: Separation of the TDI (80/20) to produce pure 2,4-TDI and a 65:35 mixture of 2,4-TDI and 2,6-TDI, known as TDI (65/35)
Chemistry
Each of the isocyanate functional groups in TDI can react with a hydroxyl group to form a urethane linkage.2,4-TDI is an asymmetrical molecule and thus has two isocyanate groups of different reactivity. The 4-position is approximately four times more reactive than the 2-position. 2,6-TDI is a symmetrical molecule and thus has two isocyanate groups of similar reactivity, similar to the 2-position on 2,4-TDI. However, since both isocyanate groups are attached to the same aromatic ring, reaction of one isocyanate group will cause a change in the reactivity of the second isocyanate group.[#endnote_TPB-3]
Hazards
Exposure to TDI and its vapors should be avoided.See also
References
- ↑
- ↑
- ↑
External links
- [International Chemical Safety Card 0339]
- [IARC Monograph: "Toluene Diisocyanates"]
- [NIOSH Pocket Guide to Chemical Hazards]
- [Hazards of TDI, MDI, and HDI] (pdf)
- [NIOSH Safety and Health Topic: Isocyanates], from the website of the National Institute for Occupational Safety and Health (NIOSH)
- For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].
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