Triacetin

Triacetin is the organic compound with the formula C₃H₅(OCOCH₃)₃. It is classified as a triglyceride, i.e., the triester of glycerol with acetic acid. It is a colorless, viscous, and odorless liquid with a high boiling point and a low melting point. It has a mild, sweet taste in concentrations lower than 500 ppm, but may appear bitter at higher concentrations.^[6] It is one of the glycerine acetate compounds.

Triacetin^[1]

Names
Systematic IUPAC name Propane-1,2,3-triyl triacetate
Other names Glycerol triacetate glycerin triacetate 1,2,3-triacetylglycerol 1,2,3-triacetoxypropane
Identifiers
CAS Number	102-76-1 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:9661 N
ChEMBL	ChEMBL1489254 N
ChemSpider	13835706 Y
ECHA InfoCard	100.002.775
EC Number	203-051-9
E number	E1518 (additional chemicals)
KEGG	D00384 Y
PubChem CID	5541
RTECS number	AK3675000
UNII	XHX3C3X673 Y
CompTox Dashboard (EPA)	DTXSID3026691
InChI InChI=1S/C9H14O6/c1-6(10)13-4-9(15-8(3)12)5-14-7(2)11/h9H,4-5H2,1-3H3 Y Key: URAYPUMNDPQOKB-UHFFFAOYSA-N Y InChI=1/C9H14O6/c1-6(10)13-4-9(15-8(3)12)5-14-7(2)11/h9H,4-5H2,1-3H3 Key: URAYPUMNDPQOKB-UHFFFAOYAH
SMILES CC(=O)OC(COC(=O)C)COC(C)=O
Properties
Chemical formula	C9H14O6
Molar mass	218.205 g·mol−1
Appearance	Oily liquid
Density	1.155 g/cm3[2]
Melting point	−78 °C (−108 °F; 195 K)[3]: 3–534
Boiling point	259 °C (498 °F; 532 K)[3]: 3–534
Solubility in water	6.1 g/100 mL[4][page needed]
Solubility in ethanol	Miscible
Solubility in benzene	soluble
Solubility in diethyl ether	soluble
Solubility in acetone	very soluble
Vapor pressure	1 Pa (0.0075 mmHg) (37.6 °C (99.7 °F; 310.8 K)) 10 Pa (0.075 mmHg) (62 °C (144 °F; 335 K)) 100 Pa (0.75 mmHg) (90 °C (194 °F; 363 K)) 1 kPa (7.5 mmHg) (124 °C (255 °F; 397 K)) 10 kPa (75 mmHg) (165 °C (329 °F; 438 K)) 100 kPa (750 mmHg) (214 °C (417 °F; 487 K))[3]: 6–88
Refractive index (nD)	1.4301 (20 °C (68 °F; 293 K))[3]: 3–534
Viscosity	23 mPas (20 °C (68 °F; 293 K))[2]
Thermochemistry[5][3]: 6–121
Heat capacity (C)	389 J⋅mol−1·K-1
Std molar entropy (S⦵298)	458.3 kJ⋅mol−1·K-1
Std enthalpy of formation (ΔfH⦵298)	−1330.8 kJ⋅mol−1
Std enthalpy of combustion (ΔcH⦵298)	4211.6 kJ⋅mol−1
Enthalpy of vaporization (ΔfHvap)	85.74 kJ⋅mol−1
Hazards[2]
NFPA 704 (fire diamond)	0 1 0
Flash point	138 °C (280 °F; 411 K)
Autoignition temperature	430 °C (806 °F; 703 K)
Explosive limits	7.73%-?
Lethal dose or concentration (LD, LC):
LD50 (median dose)	3 g/kg (rat, oral)[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Uses

Triacetin is a common food additive, for instance as a solvent in flavorings, and for its humectant function, with E number E1518 and Australian approval code A1518. It is used as an excipient in pharmaceutical products, where it is used as a humectant, a plasticizer, and as a solvent.^[7]

Potential uses

The plasticizing capabilities of triacetin have been utilized in the synthesis of a biodegradable phospholipid gel system for the dissemination of the cancer drug paclitaxel (PTX).^[8] In the study, triacetin was combined with PTX, ethanol, a phospholipid and a medium chain triglyceride to form a gel-drug complex. This complex was then injected directly into the cancer cells of glioma-bearing mice. The gel slowly degraded and facilitated sustained release of PTX into the targeted glioma cells.

Triacetin can also be used as a fuel additive as an antiknock agent for gasoline, and to improve low-temperature viscosity properties of biodiesel.^[9]

It has been considered as a possible source of food energy in artificial food regeneration systems on long space missions. It is believed to be safe to get over half of one's dietary energy from triacetin.^[10]

Synthesis

Triacetin was first prepared in 1854 by the French chemist Marcellin Berthelot. Triacetin was prepared in the 19th century from glycerol and acetic acid.^[11][12]

Its synthesis from acetic anhydride and glycerol is simple and inexpensive:

3 (CH₃CO)₂O + C₃H₅(OH)₃ → C₃H₅(OCOCH₃)₃ + 3 CH₃CO₂H

This synthesis has been conducted with catalytic sodium hydroxide and microwave irradiation to give a 99% yield of triacetin.^[13] Synthesis has also been conducted with a cobalt(II) Salen complex catalyst supported by silicon dioxide and heated to 50 °C (122 °F) for 55 minutes to give a 99% yield of triacetin.^[14]

Safety

The US Food and Drug Administration has approved it as generally recognized as safe food additive and included it in the database according to the opinion from the Select Committee On GRAS Substances (SCOGS). Triacetin is included in the SCOGS database since 1975.^[15][16]

Triacetin was not toxic to animals in studies of exposure through repeated inhalation over a relatively short period.^[17]