Toluene diisocyanate

Toluene-2,4-diisocyanate
Names
	Preferred IUPAC name 2,4-Diisocyanato-1-methylbenzene
	Other names Toluene diisocyanate; Toluene-2,4-diisocyanate; Methyl phenylene diisocyanate; Benzylene 2,4-diisocyanate; 2,4-Di(nitrogencarbonyl)toluene
Identifiers
CAS Number	2,4: 584-84-9 ; 2,6: 91-08-7;
3D model (JSmol)	2,4: Interactive image; 2,6: Interactive image;
Beilstein Reference	744602
ChEBI	2,4: CHEBI:53556 ; 2,6: CHEBI:53557;
ChEMBL	2,4: ChEMBL1086446 ; 2,6: ChEMBL1443390;
ChemSpider	2,4: 13835351 ; 2,6: 6773;
ECHA InfoCard	100.008.678
EC Number	2,4: 209-544-5; 2,6: 202-039-0;
PubChem CID	2,4: 11443; 2,6: 7040;
RTECS number	2,4: CZ6300000; 2,6: CZ6310000;
UNII	2,4: 17X7AFZ1GH ; 2,6: 78243HXH5O;
UN number	2078
CompTox Dashboard (EPA)	2,4: DTXSID7026156 ; 2,6: DTXSID2026157;
	InChI InChI=1S/C9H6N2O2/c1-7-2-3-8(10-5-12)4-9(7)11-6-13/h2-4H,1H3 Key: DVKJHBMWWAPEIU-UHFFFAOYSA-N ; 2,4: InChI=1/C9H6N2O2/c1-7-2-3-8(10-5-12)4-9(7)11-6-13/h2-4H,1H3 Key: DVKJHBMWWAPEIU-UHFFFAOYAL; 2,6: InChI=1S/C9H6N2O2/c1-7-8(10-5-12)3-2-4-9(7)11-6-13/h2-4H,1H3 Key: RUELTTOHQODFPA-UHFFFAOYSA-N;
	SMILES 2,4: Cc1ccc(cc1\N=C=O)\N=C=O; 2,6: CC1=C(C=CC=C1N=C=O)N=C=O;
Properties
Chemical formula	C9H6N2O2
Molar mass	174.2 g/mol
Appearance	Colorless liquid
Odor	sharp, pungent
Density	1.214 g/cm3, liquid
Melting point	21.8 °C (71.2 °F; 294.9 K)
Boiling point	251 °C (484 °F; 524 K)
Solubility in water	Reacts
Vapor pressure	0.01 mmHg (25°C)
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H315, H317, H318, H319, H330, H334, H335, H351, H412
Precautionary statements	P201, P202, P260, P261, P264, P271, P272, P273, P280, P281, P284, P285, P302+P352, P304+P340, P304+P341, P305+P351+P338, P308+P313, P310, P312, P320, P321, P332+P313, P333+P313, P337+P313, P342+P311, P362, P363, P403+P233, P405, P501
NFPA 704 (fire diamond)	3 1 1
Flash point	127 °C (261 °F; 400 K)
Explosive limits	0.9–9.5%
	Lethal dose or concentration (LD, LC):
LC50 (median concentration)	14 ppm (rat, 4 hr); 13.9 ppm (guinea pig, 4 hr); 9.7 ppm (mouse, 4 hr); 11 ppm (rabbit, 4 hr)
	NIOSH (US health exposure limits):
PEL (Permissible)	C 0.02 ppm (0.14 mg/m3)
REL (Recommended)	Ca
IDLH (Immediate danger)	Ca [2.5 ppm]
Related compounds
Related isocyanates	Methylene diphenyl diisocyanate; Naphthalene diisocyanate, 1,3-Diisocyanatobenzene
Related compounds	Polyurethane
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Toluene diisocyanate (TDI) is an organic compound with the formula CH₃C₆H₃(NCO)₂. Two of the six possible isomers are commercially important: 2,4-TDI (CAS: 584-84-9) and 2,6-TDI (CAS: 91-08-7). 2,4-TDI is produced in the pure state, but TDI is often marketed as 80/20 and 65/35 mixtures of the 2,4 and 2,6 isomers respectively. It is produced on a large scale, accounting for 34.1% of the global isocyanate market in 2000, second only to MDI.^[3] Approximately 1.4 billion kilograms were produced in 2000.^[4] All isomers of TDI are colorless, although commercial samples can appear yellow.

Synthesis

2,4-TDI is prepared in three steps from toluene via dinitrotoluene and 2,4-diaminotoluene (TDA). Finally, the TDA is subjected to phosgenation, i.e., treatment with phosgene to form TDI. This final step produces HCl as a byproduct and is a major source of industrial hydrochloric acid.^[4]

Distillation of the raw TDI mixture produces an 80:20 mixture of 2,4-TDI and 2,6-TDI, known as TDI (80/20). Differentiation or separation of the TDI (80/20) can be used to produce pure 2,4-TDI and a 65:35 mixture of 2,4-TDI and 2,6-TDI, known as TDI (65/35).

Description and description of reactivity

The isocyanate functional groups in TDI react with hydroxyl groups to form carbamate (urethane) links. The two isocyanate groups in Toluene diisocyanate react at different rates: 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.^[3]

Applications

Toluene diisocyanate is used in the production of rigid polyurethane foams with a high temperature stability.

It is also sometimes used in rocket propellants.^[5]

Hazards

The LD50 for TDI is 5800 mg/kg for oral contact and LC50 of 610 mg/m³ for the vapour. Despite the indicated low toxicity, TDI is classified as "very toxic" by the European Community.^[4]

In the United States, the Occupational Safety and Health Administration has set a permissible exposure limit with a ceiling at 0.02 ppm (0.14 mg/m³), while the National Institute for Occupational Safety and Health has not established a recommended exposure limit, due to the classification of toluene diisocyanate as a possible occupational carcinogen.^[6] This chemical was one of many that were stored by the company whose chemical warehouse stationed in Tianjin, China was the site of massive explosions on August 12, 2015.^[7]

Information is available on handling, personal protective equipment, exposure monitoring, transport, storage, sampling and analysis of TDI, dealing with accidents, and health and environmental themes.^[8] All major producers of TDI are members of the International Isocyanate Institute,^{[citation needed]} whose aim is the promotion of the safe handling of TDI in the workplace, community, and environment.

High-level exposure can result in reactive airways dysfunction syndrome.^{[citation needed]}

References

^ ^a ^b ^c ^d ^e ^f NIOSH Pocket Guide to Chemical Hazards. "#0621". National Institute for Occupational Safety and Health (NIOSH).
^ "Toluene-2,4-diisocyanate". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
^ ^a ^b Randall, D.; Lee, S. (2003). The Polyurethanes Book. New York: Wiley. ISBN 978-0-470-85041-1.
^ ^a ^b ^c Six, C.; Richter, F. "Isocyanates, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a14_611. ISBN 978-3527306732.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)
^ "Ababil-100/Al Fat'h". GlobalSecurity.org. Archived from the original on 15 April 2019.
^ National Institute for Occupational Safety and Health (May 1994). "Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs)". Centers for Disease Control and Prevention.
^ Ripley, Will; Jiang, Steven; Mullen, Jethro (13 August 2023). "Tianjin explosion: Dozens dead, areas of Chinese port city devastated". CNN. Retrieved 1 October 2023.
^ Allport, D. C.; Gilbert, D. S.; Outterside, S. M., eds. (2003). MDI and TDI: Safety, Health and the Environment: A Source Book and Practical Guide. Wiley. ISBN 978-0-471-95812-3.

External links

International Chemical Safety Card 0339
IARC Monograph: "Toluene Diisocyanates"
NIOSH Pocket Guide to Chemical Hazards
NIOSH Safety and Health Topic: Isocyanates, from the website of the National Institute for Occupational Safety and Health (NIOSH)
International Isocyanate Institute http://www.diisocyanates.org

[PGCH-1] ^ ^a ^b ^c ^d ^e ^f NIOSH Pocket Guide to Chemical Hazards. "#0621". National Institute for Occupational Safety and Health (NIOSH).

[2] "Toluene-2,4-diisocyanate". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).

[Randall-3] Randall, D.; Lee, S. (2003). The Polyurethanes Book. New York: Wiley. ISBN 978-0-470-85041-1.

[Ullmann-4] Six, C.; Richter, F. "Isocyanates, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a14_611. ISBN 978-3527306732.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)

[5] "Ababil-100/Al Fat'h". GlobalSecurity.org. Archived from the original on 15 April 2019.

[6] National Institute for Occupational Safety and Health (May 1994). "Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs)". Centers for Disease Control and Prevention.

[7] Ripley, Will; Jiang, Steven; Mullen, Jethro (13 August 2023). "Tianjin explosion: Dozens dead, areas of Chinese port city devastated". CNN. Retrieved 1 October 2023.

[8] Allport, D. C.; Gilbert, D. S.; Outterside, S. M., eds. (2003). MDI and TDI: Safety, Health and the Environment: A Source Book and Practical Guide. Wiley. ISBN 978-0-471-95812-3.

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