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CAS 56-81-5 Polyol Solvent / Tonicity Agent Polyol Solvent / Tonicity Agent

Synthetic Glycerol (for injection)

IUPAC: Propane-1,2,3-triol View on PubChem
CAS NUMBER
56-81-5
MOL. FORMULA
C3H8O3
MOL. WEIGHT
92.09 g/mol
Scientific Overview

Glycerol's three hydroxyl groups make it fully miscible with water and give it strong hygroscopic, viscosity-modifying, and cryoprotective properties. In parenteral formulations it is used to adjust tonicity and as a co-solvent for poorly water-soluble drugs; in oral liquids it acts as a sweetening and viscosity agent. Synthetic (petrochemical-derived) glycerol is preferred for injectable use because its manufacturing process avoids the contamination risks associated with some natural/rendered glycerin sources.

Synthetic Glycerol (glycerin) is a clear, colorless, viscous, hygroscopic triol widely used as a solvent, tonicity-adjusting agent, and humectant in injectable and oral pharmaceutical formulations. The injection grade is manufactured synthetically (from propylene) to guarantee freedom from diethylene glycol and other toxic contaminants found in some natural-source glycerin.

Full Technical Data
Chemical Name Glycerol (Glycerin)
CAS Number 56-81-5
IUPAC Name Propane-1,2,3-triol
Molecular Formula C3H8O3
Molecular Weight 92.09 g/mol g/mol
Boiling Point 290°C (decomposes)
Density 1.261 g/cm³ at 20°C
Refractive Index 1.473 at 20°C
Flash Point 176°C
Reaction Scheme
Propylene (via Epichlorohydrin or Allyl Alcohol route)
NA
NA
Synthetic Glycerol
NA
Commercial Applications

Parenteral Tonicity Agent

Adjusts osmolality of injectable solutions to isotonic levels, used in IV and IM formulations.

Co-solvent for Poorly Soluble Drugs

Enhances solubility of lipophilic APIs in injectable and oral liquid formulations.

Cryoprotection

Protects cells and biologics during freeze-thaw cycles in biologics and vaccine manufacturing.

Oral Liquid Excipient

Functions as a sweetener, viscosity modifier, and humectant in syrups and elixirs.

Market Therapeutic Focus
POLYOL SOLVENT / TONICITY AGENT PHARMACEUTICAL MANUFACTURING INJECTABLE & PARENTERAL FORMULATION VACCINE & BIOLOGICS MANUFACTURING SPECIALTY EXCIPIENTS CRO/CDMO
Scientific Literature

Diethylene Glycol Poisoning in 2006: A Report from the Panama Poison Control Center

Authors: Rentz, E.D. et al.

Clin. Infect. Dis.

Glycerin: A Literature Review for Pharmaceutical and Cosmetic Formulators

Authors: Fluhr, J.W. et al.

Skin Pharmacol. Physiol.

Pharmaceutical Applications of Glycerol

Authors: Farhadnejad, H. et al.

Int. J. Pharm.

Peer Queries & FAQs
Why must injectable glycerin be synthetically sourced?
Synthetic glycerol avoids the diethylene glycol (DEG) contamination risk historically associated with some natural or improperly refined glycerin, which has caused fatal poisoning incidents when substituted into medicines.
What role does glycerol play in injectable formulations?
It serves primarily as a tonicity-adjusting agent and co-solvent, helping dissolve lipophilic drugs and maintain isotonicity with blood plasma.
Is glycerol used in vaccines?
Yes, it is used as a stabilizer and cryoprotectant in some vaccine and biologics formulations.
What is the recommended storage condition?
Store in a tightly sealed container at room temperature; glycerol is highly hygroscopic and should be protected from moisture uptake.

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