Propylene glycol
Preferred IUPAC name: Propane-1,2-diol. Other names:Mono Propylen Glycole; monopropilen glicol;Monopropylene glycol; MPG; Monopropyleneglycol; MPG (propane-1,2-diol); propan-1,2-diol; Propane-1 ,2-diol; PROPYLENE GLYCOL; Propylene glycol; α-Propylene glycol; 1,2-Propanediol; 1,2-Dihydroxypropane; Methyl ethyl glycol; Methylethylene glycol
CAS Number: 57-55-6 racemic ; 4254-15-3 S-enantiomer. EC Number: 200-338-0; E number:E 1520 (additional chemicals)
Properties
Chemical formula: C3H8O2
Molar mass: 76.095 g·mol−1
Density: 1.036 g/cm3
Melting point: −59 °C
Boiling point: 188.2 °C
Solubility in water: Miscible
Solubility in ethanol: Miscible
Solubility in diethyl ether: Miscible
Solubility in acetone: Miscible
Solubility in chloroform: Miscible
log P: -1.34[2]
Thermal conductivity: 0.34 W/m-K (50% H2O @ 90 °C (194 °F))
Viscosity: 0.042 Pa·s
CAS NO. 57-55-6
PROPYLENE GLYCOL
FORMULA CH3CHOHCH2OH
MOL WT. 76.10
H.S. CODE: 2905.39
TOXICITY: Oral rat LD50: 20000 mg/kg
SYNONYMS: Methylethyl glycol; Methylethylene glycol; 1,2-Propanediol; alpha-Propylene glycol; Methyl glycol; Monopropylene glycol; PG; 1,2-Dihydroxypropane; 1,2-Propylene Glycol; 2-Hydroxypropanol; 2,3-Propanediol; Propane-1,2-diol; Trimethyl glycol; 1,2-Propylenglykol; Isopropylene glycol;
PHYSICAL AND CHEMICAL PROPERTIES
PHYSICAL STATE: Clear liquid
MELTING POINT:- 59 C
BOILING POINT: 185 – 189 C
SPECIFIC GRAVITY: 1.036
SOLUBILITY IN WATER: Miscible
Propylene glycol is a synthetic liquid substance that absorbs water. Propylene glycol is also used to make polyester compounds, and as a base for deicing solutions. Propylene glycol is used by the chemical, food, and pharmaceutical industries as an antifreeze when leakage might lead to contact with food. The Food and Drug Administration (FDA) has classified propylene glycol as an additive that is “generally recognized as safe” for use in food. It is used to absorb extra water and maintain moisture in certain medicines, cosmetics, or food products. It is a solvent for food colors and flavors, and in the paint and plastics industries. Propylene glycol is also used to create artificial smoke or fog used in fire-fighting training and in theatrical productions. Other names for propylene glycol are 1,2-dihydroxypropane, 1,2-propanediol, methyl glycol, and trimethyl glycol. Propylene glycol is clear, colorless, slightly syrupy liquid at room temperature. It may exist in air in the vapor form, although propylene glycol must be heated or briskly shaken to produce a vapor. Propylene glycol is practically odorless and tasteless.
Propylene Glycol is a propanediol that exists as a clear, colorless and hygroscopic liquid and consists of propane where the hydrogens at positions 1 and 2 are substituted by hydroxyl groups. Propylene glycol is used as an organic solvent and diluent in pharmaceuticals and many other industrial applications.
Propylene glycol (IUPAC name: propane-1,2-diol), according to the US National Library of Medicine and the Agency for Toxic Substances and Disease Registry, is a synthetic liquid substance that absorbs water.
It is labeled an organic compound in chemistry due to its carbon attributes. Its chemical formula is CH3CH(OH)CH2OH. It is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste.
Containing two alcohol groups, it is classed as a diol. It is miscible with a broad range of solvents, including water, acetone, and chloroform. In general, glycols are non-irritating and have very low volatility.
It is produced on a large scale primarily for the production of polymers. In the European Union, it has E-number E1520 for food applications. For cosmetics and pharmacology, the number is E490. Propylene glycol is also present in propylene glycol alginate, which is known as E405.
Propylene glycol is a compound which is GRAS (generally recognized as safe) by the US FDA (Food and Drug Administration) under 21 CFR x184.1666, and is also approved by the FDA for certain uses as an indirect food additive.
Propylene glycol is approved and used as a vehicle for topical, oral and some intravenous pharmaceutical preparations in U.S. and in Europe.
Propylene glycol is a synthetic liquid substance that absorbs water. Propylene glycol is also used to make polyester compounds, and as a base for deicing solutions. Propylene glycol is used by the chemical, food, and pharmaceutical industries as an antifreeze when leakage might lead to contact with food.
The Food and Drug Administration (FDA) has classified propylene glycol as an additive that is “generally recognized as safe” for use in food. It is used to absorb extra water and maintain moisture in certain medicines, cosmetics, or food products.
It is a solvent for food colors and flavors, and in the paint and plastics industries. Propylene glycol is also used to create artificial smoke or fog used in fire-fighting training and in theatrical productions. Other names for propylene glycol are 1,2-dihydroxypropane, 1,2-propanediol, methyl glycol, and trimethyl glycol.
Propylene glycol is clear, colorless, slightly syrupy liquid at room temperature.
It may exist in air in the vapor form, although propylene glycol must be heated or briskly shaken to produce a vapor. Propylene glycol is practically odorless and tasteless.
Propylene Glycol is a propanediol that exists as a clear, colorless and hygroscopic liquid and consists of propane where the hydrogens at positions 1 and 2 are substituted by hydroxyl groups. Propylene glycol is used as an organic solvent and diluent in pharmaceuticals and many other industrial applications.
An ingredient found in many personal-care products like shampoo, hair conditioner, and styling product, propylene glycol is widely used because of its relatively low cost and versatile nature. Its inclusion in a formula can fulfill a variety of purposes, which makes it a popular choice by the cosmetics chemist.
Propylene glycol (also known as 1,2 propanediol) is a relatively small molecule with two alcohol (hydroxyl) groups (-OH). It is a colorless, odorless liquid that is completely water-soluble. PG is a synthetic product obtained from the hydration of propylene oxide, which is derived from petroleum products.
The compound is sometimes called (alpha) α-propylene glycol to distinguish it from the isomer propane-1,3-diol, known as (beta) β-propylene glycol. Propylene glycol is chiral. Commercial processes typically use the racemate. The S-isomer is produced by biotechnological routes.
Production
Industrial
Industrially, propylene glycol is mainly produced from propylene oxide (for food-grade use). According to a 2018 source, 2.16 M tonnes are produced annually.[5] Manufacturers use either non-catalytic high-temperature process at 200 °C (392 °F) to 220 °C (428 °F), or a catalytic method, which proceeds at 150 °C (302 °F) to 180 °C (356 °F) in the presence of ion exchange resin or a small amount of sulfuric acid or alkali.
Final products contain 20% propylene glycol, 1.5% of dipropylene glycol, and small amounts of other polypropylene glycols.[7] Further purification produces finished industrial grade or USP/JP/EP/BP grade propylene glycol that is typically 99.5% or greater. Use of USP (US Pharmacopoeia) propylene glycol can reduce the risk of Abbreviated New Drug Application (ANDA) rejection.
Propylene glycol can also be obtained from glycerol, a byproduct from the production of biodiesel.[5] This starting material is usually reserved for industrial use because of the noticeable odor and taste that accompanies the final product.
Along with vegetable glycerin as the main ingredient (<1–92%) in e-liquid used in electronic cigarettes, where it is aerosolized to resemble smoke. It serves as both the carrier for substances like nicotine and cannabinoids, as well as for creating a vapor which resembles smoke.
Miscellaneous applications
A bottle of flavored e-liquid for vaping shows propylene glycol as one of the main ingredients along with vegetable glycerin.
Propylene glycol (often abbreviated ‘PG’) has many applications. Some common applications see PG used:
As a solvent for many substances, both natural and synthetic.
As a humectant (E1520).
In veterinary medicine as an oral treatment for hyperketonaemia in ruminants.
In the cosmetics industry, where PG is very commonly used as a carrier or base for various types of makeup.
For trapping and preserving insects (including as a DNA preservative).
For the creation of theatrical smoke and fog in special effects for film and live entertainment. So-called ‘smoke machines’ or ‘hazers’ vaporize a mixture of PG and water to create the illusion of smoke. While many of these machines use a PG-based fuel, some use oil. Those which use PG do so in a process which is identical to how electronic cigarettes work; utilizing a heating element to produce a dense vapor. The vapor produced by these machines has the aesthetic look and appeal of smoke, but without exposing performers and stage crew to the harms and odors associated with actual smoke.[25][26]
As an additive in PCR to reduce the melting temperature of nucleic acids for targeting of GC rich sequences.
Safety in humans
When used in average quantities, propylene glycol has no measurable effect on development and/or reproduction on animals and probably does not adversely affect human development or reproduction.[27] The safety of electronic cigarettes—which utilize PG-based preparations of nicotine or THC and other cannabinoids—is the subject of much controversy.
Oral administration
The acute oral toxicity of propylene glycol is very low, and large quantities are required to cause perceptible health effects in humans; in fact, propylene glycol is three times less toxic than ethanol.[31] Propylene glycol is metabolized in the human body into pyruvic acid (a normal part of the glucose-metabolism process, readily converted to energy), acetic acid (handled by ethanol-metabolism), lactic acid (a normal acid generally abundant during digestion),and propionaldehyde (a potentially hazardous substance). According to the Dow Chemical Company, The LD50 (Lethal Dose that kills in 50% of tests) for rats is 20 g/kg (rat/oral).
Toxicity generally occurs at plasma concentrations over 4 g/L, which requires extremely high intake over a relatively short period of time, or when used as a vehicle for drugs or vitamins given intravenously or orally in large bolus doses.[38] It would be nearly impossible to reach toxic levels by consuming foods or supplements, which contain at most 1 g/kg of PG, except for alcoholic beverages in the US which are allowed 5 percent = 50g/kg. Cases of propylene glycol poisoning are usually related to either inappropriate intravenous administration or accidental ingestion of large quantities by children.[40]
The potential for long-term oral toxicity is also low. In an NTP continuous breeding study, no effects on fertility were observed in male or female mice that received propylene glycol in drinking water at doses up to 10,100 mg/kg bw/day. No effects on fertility were seen in either the first or second generation of treated mice. In a 2-year study, 12 rats were provided with feed containing as much as 5% propylene glycol, and showed no apparent ill effects. Because of its low chronic oral toxicity, propylene glycol was classified by the U. S. Food and Drug Administration as “generally recognized as safe” (GRAS) for use as a direct food additive, including frozen foods such as ice cream and frozen desserts.
The GRAS designation is specific to its use in food, and does not apply to other uses.
Inhalation
The potential carcinogen (some studies revealed no cancerinogenic evidence of such product) formaldehyde is suspected to be a product of propylene glycol and glycerol vapor degradation (there being no credible proof of this causality).[45] No indication can be given whether a harmful concentration of this product in the air can be reached.
Skin, eye and inhalation contact
Propylene glycol is essentially non-irritating to the skin. Undiluted propylene glycol is minimally irritating to the eye, producing slight transient conjunctivitis; the eye recovers after the exposure is removed.
A 2018 human volunteer study found that 10 male and female subjects undergoing 4 hours exposures to concentrations of up to 442 mg/m3 and 30 minutes exposures to concentrations of up to 871 mg/m3 in combination with moderate exercise did not show pulmonary function deficits, or signs of ocular irritation, with only slight symptoms of respiratory irritation reported.
Inhalation of propylene glycol vapors appears to present no significant hazard in ordinary applications.[49] Due to the lack of chronic inhalation data, it is recommended that propylene glycol not be used in inhalation applications such as theatrical productions, or antifreeze solutions for emergency eye wash stations.
Recently, propylene glycol (commonly alongside glycerol) has been included as a carrier for nicotine and other additives in e-cigarette liquids, the use of which presents a novel form of exposure.
The potential hazards of chronic inhalation of propylene glycol or the latter substance as a whole are as-yet unknown.
According to a 2010 study, the concentrations of PGEs (counted as the sum of propylene glycol and glycol ethers) in indoor air, particularly bedroom air, has been linked to increased risk of developing numerous respiratory and immune disorders in children, including asthma, hay fever, eczema, and allergies, with increased risk ranging from 50% to 180%.
This concentration has been linked to use of water-based paints and water-based system cleansers. However, the study authors write that glycol ethers and not propylene glycol are the likely culprit.
Propylene glycol has not caused sensitization or carcinogenicity in laboratory animal studies, nor has it demonstrated genotoxic potential.
Intravenous administration
Studies with intravenously administered propylene glycol have resulted in LD50 values in rats and rabbits of 7 mL/kg BW. Ruddick (1972) also summarized intramuscular LD50 data for rat as 13-20 mL/kg BW, and 6 mL/kg BW for the rabbit.
Adverse effects to intravenous administration of drugs that use propylene glycol as an excipient have been seen in a number of people, particularly with large bolus dosages.
Responses may include CNS depression, “hypotension, bradycardia, QRS and T abnormalities on the ECG, arrhythmia, cardiac arrhythmias, seizures, agitation, serum hyperosmolality, lactic acidosis, and haemolysis”.
A high percentage (12% to 42%) of directly-injected propylene glycol is eliminated or secreted in urine unaltered depending on dosage, with the remainder appearing in its glucuronide-form. The speed of renal filtration decreases as dosage increases, which may be due to propylene glycol’s mild anesthetic / CNS-depressant -properties as an alcohol.
In one case, intravenous administration of propylene glycol-suspended nitroglycerin to an elderly man may have induced coma and acidosis. However, no confirmed lethality from propylene glycol was reported.
Animals
Propylene glycol is an approved food additive for dog and sugar glider food under the category of animal feed and is generally recognized as safe for dogs,with an LD50 of 9 mL/kg. The LD50 is higher for most laboratory animals (20 mL/kg).However, it is prohibited for use in food for cats due to links to Heinz body formation and a reduced lifespan of red blood cells.
Heinz body formation from MPG has not been observed in dogs, cattle, or humans.
Allergic reaction
Estimates on the prevalence of propylene glycol allergy range from 0.8% (10% propylene glycol in aqueous solution) to 3.5% (30% propylene glycol in aqueous solution). The North American Contact Dermatitis Group (NACDG) data from 1996 to 2006 showed that the most common site for propylene glycol contact dermatitis was the face (25.9%), followed by a generalized or scattered pattern (23.7%).
Investigators believe that the incidence of allergic contact dermatitis to propylene glycol may be greater than 2% in patients with eczema or fungal infections, which are very common in countries with lesser sun exposure and lower-than-normal vitamin D balances. Therefore, propylene glycol allergy is more common in those countries.
Because of its potential for allergic reactions and frequent use across a variety of topical and systemic products, propylene glycol was named the American Contact Dermatitis Society’s Allergen of the Year for 2018. Recent publication from The Mayo Clinic reported 0.85% incidence of positive patch tests to propylene glycol (100/11,738 patients) with an overall irritant rate of 0.35% (41/11,738 patients) during a 20-year period of 1997–2016.
87% of the reactions were classified as weak and 9% as strong. The positive reaction rates were 0%, 0.26%, and 1.86% for 5%, 10%, and 20% propylene glycol respectively, increasing with each concentration increase. The irritant reaction rates were 0.95%, 0.24%, and 0.5% for 5%, 10%, and 20% propylene glycol, respectively.
Propylene glycol skin sensitization occurred in patients sensitive to a number of other concomitant positive allergens, most common of which were: Myroxylon pereirae resin, benzalkonium chloride, carba mix, potassium dichromate, neomycin sulfate; for positive propylene glycol reactions, the overall median of 5 and mean of 5.6 concomitant positive allergens was reported.
Environmental
Propylene glycol occurs naturally, probably as the result of anaerobic catabolism of sugars in the human gut. It is degraded by vitamin B12-dependent enzymes, which convert it to propionaldehyde.[72]
Propylene glycol is expected to degrade rapidly in water from biological processes, but is not expected to be significantly influenced by hydrolysis, oxidation, volatilization, bioconcentration, or adsorption to sediment.[73] Propylene glycol is readily biodegradable under aerobic conditions in freshwater, in seawater and in soil. Therefore, propylene glycol is considered as not persistent in the environment.
Propylene glycol exhibits a low degree of toxicity toward aquatic organisms. Several guideline studies available for freshwater fish with the lowest observed effect concentration of 96-h LC50 value of 40,613 mg/l in a study with Oncorhynchus mykiss. Similarly, the effect concentration determined in marine fish is a 96-h LC50 of >10,000 mg/l in Scophthalmus maximus.
1,2-propanediol; Propane-1,2-diol; Propylene glycol; CAS names: 1,2-Propanediol. IUPAC names: 1,2 propylene glycol; 1,2-propandiol; 1,2-Propane diol; 1,2-Propanediol; 1,2-Propylene glycol; Mono Propylen Glycole; monopropilen glicol;Monopropylene glycol; MPG; Monopropyleneglycol; MPG (propane-1,2-diol); propan-1,2-diol; Propane-1 ,2-diol; PROPYLENE GLYCOL
Trade names
(.+-.)-1,2-Propanediol
(.+-.)-Propylene glycol
(RS)-1,2-Propanediol
1,2-DIHYDROXYPROPANE
1,2-Propandiol
1,2-Propanediol
1,2-Propylene glycol
2-Hydroxypropanol
Agent I804
CACAO RESINOID 90% PG
Methyl ethylene glycol
Monopropylene Glycol
Monopropylene glycol
MPG
PG(P)
propane-1,2-diol
PROPYLENE GLYCOL
Propylene glycol (all grades)
RADIANOL 4713
RADIANOL 4718
RADIANOL 4740
Other identifiers
1194046-20-2
CAS number
1194046-20-2
Deleted CAS number
190913-75-8
CAS number
190913-75-8
Deleted CAS number
4254-16-4
CAS number
4254-16-4
Deleted CAS number
57-55-6
1,2-propanediol
propylene glycol
propane-1,2-diol
57-55-6
1,2-Propylene glycol
1,2-dihydroxypropane
2-Hydroxypropanol
Methylethyl glycol
Methylethylene glycol
Isopropylene glycol
Monopropylene glycol
Dowfrost
Sirlene
Trimethyl glycol
2,3-Propanediol
Propylene Glycol USP
Solargard P
alpha-Propyleneglycol
Solar Winter BAN
dl-Propylene glycol
DL-1,2-Propanediol
1,2-Propylenglykol
(RS)-1,2-Propanediol
(+-)-1,2-Propanediol
PG 12
(+-)-Propylene glycol
FEMA No. 2940
propylenglycol
alpha-Propylene glycol
Caswell No. 713
(+/-)-1,2-propanediol
1,2-Propylenglykol [German]
Prolugen
.alpha.-Propylene glycol
1,2-(RS)-Propanediol
1,2-propandiol
1,2-propane diol
1,2-propane-diol
Propan-1,2-Diol
L-1,2-propanediol
CHEBI:16997
HOCH2CH(OH)Me
MeCH(OH)CH2OH
EINECS 200-338-0
S-(+)-Propylene glycol
1,2-Propanediol, ACS reagent
(+/-)-Propylene glycol
General lube
1,2-Propanediol, 99%, extra pure
Propylene Glycol (Propane-1,2-diol)
1,2-Propanediol, 99+%, for analysis
CAS-57-55-6
1,2 Propanediol
1,2-propanediol
propylene glycol
propane-1,2-diol
57-55-6
1,2-Propylene glycol
1,2-dihydroxypropane
2-Hydroxypropanol
Methylethyl glycol
Methylethylene glycol
Isopropylene glycol
Monopropylene glycol
Dowfrost
Sirlene
Trimethyl glycol
2,3-Propanediol
Propylene Glycol USP
Solargard P
alpha-Propyleneglycol
Solar Winter BAN
dl-Propylene glycol
DL-1,2-Propanediol
Ucar 35
Sentry Propylene Glycol
1,2-Propylenglykol
(RS)-1,2-Propanediol
(+-)-1,2-Propanediol
PG 12
(+-)-Propylene glycol
FEMA No. 2940
propylenglycol
alpha-Propylene glycol
Caswell No. 713
(+/-)-1,2-propanediol
1,2-Propylenglykol [German]
Prolugen
.alpha.-Propylene glycol
1,2-(RS)-Propanediol
Ilexan P
AI3-01898
1,2-propandiol
1,2-propane diol
1,2-propane-diol
EPA Pesticide Chemical Code 068603
Propan-1,2-Diol
L-1,2-propanediol
CHEBI:16997
HOCH2CH(OH)Me
MeCH(OH)CH2OH
EINECS 200-338-0
S-(+)-Propylene glycol
(±)-1,2-propanediol
(±)-1,2-Propanediol
(±)-1,2-Propanediol
(±)-Propylene glycol
(±)-Propylene glycol
(±)-Propylene glycol
(RS)-1,2-Propanediol
1,2-(RS)-Propanediol
1,2-PDO
1,2-Propandiol
1,2-propane-diol
1,2-Propanediol [ACD/Index Name]
1,2-propylene glycol
1,2-Propyleneglycol
200-338-0 [EINECS]
57-55-6 [RN]
DL-1,2-PROPANEDIOL
DL-PROPYLENE GLYCOL
MFCD00064272 [MDL number]
Propan-1,2-diol
Propane-1,2-diol
propanediol [Wiki]
Propylene glycol [ACD/IUPAC Name] [Wiki]
Propylène glycol [French] [ACD/IUPAC Name]
PROPYLENE GLYCOL, (R)-
PROPYLENE GLYCOL, (S)-
Propylenglycol [German] [ACD/IUPAC Name]
Propylenglycolum
(9Z)-Octadecenoic acid
(Z)-Octadec-9-enoic acid
1,2-Dihydroxypropane
1,2-Propanediol 100 µg/mL in Methanol
1,2-Propanediol|Propylene glycol
1,2-Propanediol-d6
1,2-Propylenglykol [German]
1,2-丙二醇 [Chinese]
109-86-4 [RN]
123120-98-9 [RN]
198333-86-7 [RN]
2,3-Propanediol
203-713-7 [EINECS]
25322-68-3 [RN]
25322-69-4 [RN]
2-Hydroxypropanol
4254-14-2 [RN]
4254-15-3 [RN]
500-039-8 [EINECS]
52910-80-2 [RN]
58161-11-8 [RN]
63625-56-9 [RN]
80156-55-4 [RN]
a-Propylene glycol
CH3CH(OH)CH2OH
Chilisa FE
cis-9-Octadecenoic acid
cis-Oleic acid
cis-δ(9)-octadecenoic acid
ETHOXY, 2-HYDROXY-1-METHYL-
HOCH2CH(OH)CH3
HOCH2CH(OH)Me
Ilexan P
Isopropylene glycol
JEFFCOOL P150
MeCH(OH)CH2OH
METHYL GLYCOL
Methylethyl glycol
Methylethylene glycol
Monopropylene glycol
octadec-9-enoic acid
Oelsaeure
PGO
Poly(propylene glycol) average Mw 400
PPD
Prolugen
Propan-1,2-diol, GlenDry, anhydrous
PROPOXY, 2-HYDROXY-
Propylene glycol, 99%
S-1,2-PROPANEDIOL
Sirlene
Solar Winter BAN
Solargard P
Tert-butyl 4-(3-amino-2-nitrophenyl)piperazine-1-carboxylate
Trimethyl glycol
WLN: QY1&1Q
α-Propylene glycol
α-Propylene glycol
α-Propyleneglycol