Abstract  Aerobic biodegradation of tripropylene glycol (PG3) was investigated under the conditions of the OECD screening test 301E and the Continuous Flow Activated Sludge Simulation test (CFAS). A modified two-chamber facility with a denitrification stage was used for the CFAS test. Primary PG3 biodegradation was measured by the HPLC with fluorimetric detection and analyte derivatisation. Metabolites were identified by LC-MS with electrospray ionisation and GC-MS with electron impact ionisation, as well as semiquantitatively determined by the LC-MS technique. PG3 was found to be inherently biodegradable and it exhibits a strong poisonous effect on activated sludge after exceeding the threshold concentration (10 mg l(-1)). Metabolite accumulation onto the activated sludge is probably responsible for this poisonous effect. Probable biotransformation products of tripropylene glycol under the aerobic conditions include metabolites with a single terminal aldehyde or a ketone group and metabolites with two terminal aldehyde or ketone groups. Their concentration rises at the end of the OECD screening test.

Abstract  In a pollution prevention and chemical substitution effort, the U.S. Air Force and Navy formed a joint initiative to find safer, more environmentally acceptable jet fuel system icing inhibitors (FSII) for military aircraft. Standard biochemical oxygen demand (BOD) analysis and variations of the BOD procedure were used as simple screening tools to evaluate the potential for aquatic biodegradation and microbial toxicity of proposed FSIIs. This laboratory evaluation of biological properties allows prediction of the biotreatability of the chemicals in wastewater treatment plants, and their potential application as biocides at higher concentrations. The current FSII, diethylene glycol monomethyl ether (DiEGME) was evaluated along with two new candidate compounds, dipropylene glycol and glycerol formal. At a low concentration (3.5 mg/L), DiEGME exerted a BOD5 of about 27% of theoretical oxygen demand. Test concentrations of ≥7 mg/L had decreasing oxygen consumption rate and extent, typical of a material with potential aquatic microbial toxicity. Dipropylene glycol began to moderately degrade only after more than 3 weeks exposure to microorganisms obtained from raw sewage. Glycerol formal showed no signs of biodegradation during a 5‐week test period. In a simple microbial toxicity test DiEGME was most toxic, dipropylene glycol was moderately toxic, and glycerol formal showed little toxicity. At low concentrations (7 mg/L), none of the chemicals significantly inhibited microbial activity (P=0.34).

Abstract  Glycols are diols, compounds containing two hydroxyl groups attached to separate carbon atoms. In an aliphatic chain, ethylene glycol, is the simplest glycol. Diethylene, triethylene, and tetraethylene glycols are oligomers of ethylene glycol. Polyglycols are higher molecular weight adducts of ethylene oxide and are distinguished by intervening ether linkages in the hydrocarbon chain. The first commercial application of the Lefort direct ethylene oxidation to ethylene oxide followed by hydrolysis of ethylene oxide remains the main commercial source of ethylene glycol production. The uses for ethylene glycol are numerous. Some of the applications are polyester resins for fiber, PET containers, and film applications; all‐weather automotive antifreeze and coolants, defrosting and deicing aircraft; heat‐transfer solutions for coolants for gas compressors, heating, ventilating, and air‐conditioning systems; water‐based formulations such as adhesives, latex paints, and asphalt emulsions; manufacture of capacitors; and unsaturated polyester resins. The oligomers also have excellent water solubility but are less hygroscopic and have somewhat different solvent properties. The largest commercial use of ethylene glycol is its reaction with dicarboxylic acids to form linear polyesters. In addition to oligomers ethylene glycol derivative classes include monoethers, diethers, esters, acetals, and ketals as well as numerous other organic and organometallic molecules. The propylene glycol family of chemical compounds consists of monopropylene glycol (PG), dipropylene glycol (DPG), and tripropylene glycol (TPG). These chemicals are manufactured as copoducts and are used commercially in a large variety of applications. They are available as highly purified products which meet well‐defined manufacturing and sales specifications. All commercial production is via the hydrolysis of propylene oxide. The propylene glycols are clear, viscous, colorless liquids that have very little odor, a slightly bittersweet taste, and low vapor pressures. The most important member of the family is monopropylene glycol. All of the glycols are totally miscible with water. Propylene glycol, when produced according to the U.S. Food and Drug Administration good manufacturing practice guidelines at a registered facility, meets the requirements of the U.S. Food, Drug, and Cosmetic Act. It is listed in the regulation as a direct additive for specified foods and is classified as generally recognized as safe (GRAS). Because of its low human toxicity and desirable formulation properties it has been an important ingredient for years in food, cosmetic, and pharmaceutical products. Glycols such as neopentyl glycol, 2,2,4‐trimethyl‐1,3‐pentanediol, 1,4‐cyclohexanedimethanol, and hydroxypivalyl hydroxypivalate are used in the synthesis of polyesters and urethane foams. Commercial preparation of neopentyl glycol can be via an alkali‐catalyzed condensation of isobutyraldehyde with 2 moles of formaldehyde (crossed Cannizzaro reaction). 2,2,4‐Trimethyl‐1,3‐pentanediol can be produced by hydrogenation of the aldehyde trimer resulting from the aldol condensation of isobutyraldehyde. The manufacture of 1,4‐cyclohexanedimethanol can be accomplished by the catalytic reduction under pressure of dimethyl terephthalate in a methanol solution. Hydroxypivalyl hydroxypivalate may be produced by the esterification of hydoxypivalic acid with neopentyl glycol or by the intermolecular oxidation–reduction (Tishchenko reaction) of hydroxypivaldehyde using an aluminum alkoxide catalyst. Polyester resins produced from of the glycols, are useful for preparation of coatings exhibiting a combination of hydrolytic stability, excellent weather resistance, and good flexibility.

Abstract  The oxidative decomposition of two structural isomers of dipropylene glycol, i.e. 2,4‐dimethyl‐3‐oxapentandiol‐1,5 (1) and 4‐oxaheptandiol‐2,6 (2) was studied. The maximum rate of oxidation of glycol 1 was ca. 20 times lower than that of glycol 2. In the products of oxidation 15 different compounds were detected for the former glycol and 20 compounds for the latter. The products of decomposition were the mixtures of water and carboxy acid, acetal, alcohol, aldehyde, ketone, ester, unsaturated ether and hydroperoxy type of compounds of different structure. The mechanism of product formation is discussed.

Abstract  Identification and Use: Dipropylene Glycol is used as medication, as an antifreeze agent, in air sanitation, and as a stabilizer in cosmetic preparations. It is also used as an intermediate for polyester resins, solvent extraction of aromatic hydrocarbons, steam set printing inks, stabilizer in cosmetics. As an inert ingredient, dipropylene glycol facilitates delivery of formulated pesticide chemical products that are used as herbicides, fungicides, insecticides, growth regulators and attractants on various commodities. It is also used in targeting odor-causing bacteria, animal pathogenic bacteria (G- and G+ vegetative), and animal viruses. Human Toxicity Studies: Repeated application of a shaving preparation containing 7.2% dipropylene glycol did not induce sensitization in 50 subjects when applied in 24/48 hr (presumably covered) patches, 3 days/wk for 3 weeks, followed by a challenge patch after a 2 wk rest period. Covered 48 hr application of a 50% solution of dipropylene glycol (DiPG; unspecified solvent) caused irritation in 14 of 34 persons and was equivocally irritant in a further 17. No local effects were induced when 20% DiPG in petrolatum was in 48 hr covered contact with the skin of an unspecified number of volunteers. Similarly, no effects were observed in 59 subjects exposed to a shaving preparation containing 7.2% DiPG in a 4 wk controlled use test or in 101 subjects following 48 hr uncovered contact, repeated after 2 wk in conjunction with exposure to UV light. However, the same shaving preparation in 48 hr covered contact with the skin, caused mild irritation in 6 of 101 subjects, with an additional two subjects also giving mild reactions when the patch was applied 2 wk later. It is more acutely depressant to CNS than ethylene, diethylene or propylene glycol. A case of a 32-year-old man who ingested more than 500 mL of dipropylene glycol-containing Fantasia fog solution (High Energy Lighting, Houston, TX) and subsequently developed acute renal failure, polyneuropathy, and myopathy. The toxicological profiles of monopropylene glycol (MPG), dipropylene glycol (DPG), tripropylene glycol (TPG) and polypropylene glycols (PPG; including tetra-rich oligomers) are collectively reviewed, and assessed considering regulatory toxicology endpoints. None of the glycols reviewed presented evidence of carcinogenic, mutagenic or reproductive/developmental toxicity potential to humans. Animal Toxicity Studies: Undiluted /dipropylene glycol/ caused mild irritation when 500 mg was applied to rabbit skin for 24 hours. When dipropylene glycol was applied repeatedly for prolonged periods (10 applications in 12 days) to skin of rabbits it had negligible irritating action and there was no indication that toxic quantities were absorbed through intact skin. Rabbits /were given/ 2-4 g/kg bw administered iv for 1-21 days. Two animals died at the fourth day with lesions in the kidneys. The remaining 8 were killed during the following 21 days. The kidneys of 3 animals exhibited similar lesions and one of these also had involvement of the liver. /New Zealand white/... rabbits (24/group) were artificially inseminated /and given 200, 400, 800, 1200 mg/kg bw/day by gavage on days 6-19 of gestation/. Animals were observed daily for clinical signs of toxicity. Mean food and body weights were calculated for each group on gestation days (GD) 0, 6, 9, 12, 15, 25, and 30. All animals were killed on GD 30 and examined for maternal body and organ weights, implant status, fetal weight, sex and morphological development. No maternal lethality occurred in the study. Pregnancy rates were 95%, 83%, 91%, and 82% in the control to high dose dipropylene glycol (DPG) groups, respectively. No effect that could be attributed to exposure to DPG was noted on maternal body weight, food consumption, or clinical signs. Necropsy of the maternal animals revealed no effects on kidney and liver weights. In utero DPG exposure did not affect the frequency of post-implantation loss, mean fetal body weight per litter, or external, visceral, or skeletal malformation. NOEL >1200 mg/kg/day. /Tested externally on eyes, rated numerically on scale of 1 to 10 according to degree of injury observed after 24 hr, paying particular attention to condition of cornea. Most severe injuries have been rated 10/. Rats received 12% /dipropylene glycol/ in the diet for 15 weeks. The treatment resulted in depression of running activity. Moderate degenerative changes in kidneys were found. ...The concentration of 10% /dipropylene glycol/ in drinking water caused death in some animals. Histology examination revealed hydropic degeneration of kidney tubular epithelium and liver parenchyma. Rats were not affected by 5% dipropylene glycol in their drinking water for 77 days. ...Administration level of 10%, some died with hydropic degeneration of kidney tubular epithelium and liver parenchyma. ...Effects were similar to those of diethylene glycol but less severe and less uniformly produced. Time-mated /Sprague-Dawley/ rats were dosed with /800, 2000, or 5000 mg/kg/day dipropylene glycol/ (DiPG) or the distilled deionized water vehicle /by gavage/. Animals were observed daily beginning on gestation day (GD) 6 for clinical signs of toxicity. All sperm-positive rats were killed on GD20. The maternal body, liver and intact uterus were weighed and corpora lutea were counted. The fetuses were examined in detail. Maternal toxicity and lethality were observed at 2000 and 5000 mg/kg/day (mortality rate: 4% and 9%), establishing the maternal NOAEL as 800 mg/kg/day. There were no significant differences between the DiPG exposed groups and the control. NOAEL was 5000 mg/kg/day. DiPG has no teratogenetic or embryonal effect. Dipropylene glycol markedly stimulated choleresis, /SRP: Secretion of bile/, when injected intraduodenally at 1 mL/kg into rats. Propylene glycol and dipropylene glycol were tested for mutagenic or genotoxic potential and found to be negative in a battery of studies: a bacterial gene mutation assay using Salmonella typhimurium, and in vitro Chinese hamster ovary (CHO) mutation assay, an in vitro Chinese hamster ovary (CHO) chromosomal aberration assay and an in vitro sister chromatid exchange assay. Dogs... after survival of repeated gastric dosage of dipropylene glycol showed only moderate degenerative changes in kidneys and only minimal evidence of liver damage. Ecotoxicity Studies: /Authors/ were able to feed chicks a diet containing 5% dipropylene glycol for 27 days without adverse effects. The chicks were unable to use it as an energy source.

Abstract  1,2‐Propanediol, [57‐55‐6], propylene glycol, HOCH2CH(CH3)OH, is very similar to ethylene glycol in its physical and chemical properties (→ Ethylene Glycol). The first reported description of 1,2‐propanediol was by Wurtz in 1859 1. Industrial‐scale synthesis of 1,2‐propanediol from propylene oxide (→ Propylene Oxide) and water began in the 1930s. Current production uses this same process, which leads simultaneously to di‐ and tripropylene glycols. The worldwide capacity for 1,2‐propanediol was predicted at 2.56 × 106 t in 2017 2. 1,2‐Propanediol finds use in diverse applications, such as unsaturated polyesters (→ Polyester Resins, Unsaturated) for thermoset composites, food chemistry, food processing equipment, cosmetics, pharmaceuticals, as well as deicers and automotive antifreeze components (→ Antifreezes).