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.^[6] 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.^[7] It is one of the glycerine acetate compounds.

Triacetin^[1]

Names
Systematic IUPAC name Propane-1,2,3-triyl triacetate
Other names Glycerol triacetate[2] 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[3]
Melting point	−78 °C (−108 °F; 195 K) at 760 mmHg[2]
Boiling point	259 °C (498 °F; 532 K) at 760 mmHg[2]
Solubility in water	6.1 g/100 mL[2]
Solubility	Miscible in EtOH Soluble in C6H6, (C2H5)2O, acetone[2]
Vapor pressure	0.051 Pa (11.09 °C) 0.267 Pa (25.12 °C) 2.08 Pa (45.05 °C)[4] ln(P/Pa)=22.819-4493/T(K)-807000/T(K)²
Refractive index (nD)	1.4301 (20 °C)[2] 1.4294 (24.5 °C)[4]
Viscosity	23 cP (20 °C)[3]
Thermochemistry
Heat capacity (C)	389 J/mol·K[5]
Std molar entropy (S⦵298)	458.3 J/mol·K[5]
Std enthalpy of formation (ΔfH⦵298)	−1330.8 kJ/mol[5]
Std enthalpy of combustion (ΔcH⦵298)	4211.6 kJ/mol[5]
Hazards
NFPA 704 (fire diamond)	[3] 1 1 0
Flash point	138 °C (280 °F; 411 K)[3]
Autoignition temperature	430 °C (806 °F; 703 K)[3]
Explosive limits	7.73%[3]
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1100 mg/kg (mice, oral)[3]
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.^[8]

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).^[9] 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 which can reduce engine knocking in gasoline, and to improve cold and viscosity properties of biodiesel.^[10]

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.^[11]

Synthesis

Triacetin was first prepared in 1854 by the French chemist Marcellin Berthelot.^[12] Triacetin was prepared in the 19th century from glycerol and acetic acid.^[13]

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

3 (CH₃CO)₂O + 1 C₃H₅(OH)₃ → 1 C₃H₅(OCOCH₃)₃ + 3 CH₃CO₂H

This synthesis has been conducted with catalytic sodium hydroxide and microwave irradiation to give a 99% yield of triacetin.^[14] It has also been conducted with a cobalt(II) Salen complex catalyst supported by silicon dioxide and heated to 50 °C for 55 minutes to give a 99% yield of triacetin.^[15]

Safety

The US Food and Drug Administration has approved it as generally recognized as safe^[16] 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.^[17]

Triacetin was not toxic to animals in studies of exposure through repeated inhalation over a relatively short period.^[18]