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Triol

A triol is an organic compound containing three hydroxyl (-OH) functional groups attached to a carbon chain or ring structure, distinguishing it from diols (with two) and monohydric alcohols (with one).^[1] These polyols exhibit versatile reactivity due to their multiple -OH groups, enabling applications in synthesis and materials science.^[2] The prototypical and most abundant triol is glycerol (also known as 1,2,3-propanetriol or glycerin), a viscous, sweet-tasting liquid with the formula C₃H₈O₃, produced as a byproduct of biodiesel and soap manufacturing.^[3] Glycerol serves as a humectant, solvent, and sweetener in food and pharmaceuticals, while also functioning as an antifreeze, lubricant in oil fields, and component in explosives like nitroglycerin.^[3] Its biocompatibility supports uses in medical devices, cosmetics, and as an osmolyte in biological systems.^[3] Beyond glycerol, triols encompass a diverse class including aliphatic, aromatic, and cyclic variants, each with specialized roles. For instance, trimethylolpropane (TMP), a branched triol, acts as a cross-linking agent in polyurethane and polyester resins, enhancing mechanical properties in coatings and adhesives.^[4] Aromatic triols like pyrogallol (benzene-1,2,3-triol) find applications in photography as a developing agent, hair dyes, and antioxidant synthesis, owing to its redox properties.^[5] In pharmaceuticals, compounds such as nalbuphine (a morphinan-3,6,14-triol derivative) are used as analgesics for pain management.^[4] Overall, triols are essential intermediates in polymer chemistry, enabling the production of biodegradable materials, and in organic reactions for heterocycles and nucleosides.^[4]

Definition and Nomenclature

Definition

A triol is an organic compound that contains exactly three hydroxyl (-OH) groups attached to a carbon-based skeleton, classifying it as a type of polyol.^[1]^[6] These compounds are characterized by their multiple alcohol functional groups, which impart specific reactivity and solubility properties inherent to alcohols. Triols are distinguished from related polyols such as diols, which possess two -OH groups, and tetraols, which have four, solely by the precise count of three hydroxyl groups per molecule. This structural specificity defines triols within organic nomenclature and functional group chemistry. For saturated acyclic triols, the general molecular formula is C_nH_{2n+2}O_3, where n represents the number of carbon atoms, reflecting the addition of three oxygen atoms from the hydroxyl groups to a saturated hydrocarbon backbone.^[7] The term "triol" originates from the Greek prefix "tri-" denoting three, combined with the suffix "-ol" derived from "alcohol," and entered usage in organic chemistry during the mid-19th century as classification of polyhydric alcohols advanced.^[7] A representative example is glycerol (propane-1,2,3-triol), a simple triol central to many biochemical processes.^[8]

Nomenclature

In the International Union of Pure and Applied Chemistry (IUPAC) nomenclature system, triols are named by identifying the longest continuous carbon chain that includes the maximum number of hydroxy groups, replacing the terminal "-e" of the corresponding alkane name with the suffix "-triol," and specifying the positions of the three hydroxy groups with the lowest possible locants. For example, the simplest triol, featuring three consecutive hydroxy groups on a three-carbon chain, is designated propane-1,2,3-triol, which is the preferred IUPAC name (PIN). This approach ensures systematic naming that reflects the compound's structure while prioritizing the principal characteristic group, the hydroxy function. Numbering of the parent chain begins from the end that assigns the lowest set of locants to the hydroxy groups; if a choice remains, the chain is numbered to give the lowest locant to the hydroxy group that appears first in the name. When multiple hydroxy groups are present, multiplicative prefixes such as "di," "tri," or higher are used without spaces or hyphens between the locants and the suffix, as in butane-1,2,4-triol. Substituents are cited as prefixes in alphabetical order before the parent name, maintaining the lowest locant rule for the principal chain. For cyclic triols, the name is formed by adding the suffix "-triol" with appropriate locants to the name of the cycloalkane parent hydride, selecting the numbering that provides the lowest possible locants for the hydroxy groups. An example is cyclohexane-1,2,3-triol, where the positions indicate adjacent hydroxy groups on the six-membered ring. In cases of fused or bridged systems, additional rules from the von Baeyer system may apply, but the hydroxy suffixes retain priority in numbering. Common or trivial names persist for certain well-known triols, often derived from historical or industrial contexts, though they are not preferred in formal IUPAC usage. Propane-1,2,3-triol is universally recognized as glycerol, a name originating from its sweet taste and role in glycerides. Similarly, hexane-1,2,6-triol is commonly referred to as 1,2,6-hexanetriol, reflecting its linear chain structure without a more simplified trivial designation.^[9] Branched triols incorporate substituent prefixes into the parent chain name, ensuring the chain with the maximum number of hydroxy groups is chosen as the parent; for instance, the branched compound with a methyl group at the central carbon is named 2-methylpropane-1,2,3-triol. Unsaturated triols integrate indicators for double or triple bonds into the parent name using infixes like "-en-" or "-yn-," positioned according to the lowest locant rule for all functional features combined, as in pent-2-ene-1,4,5-triol. These conventions extend the systematic framework to more complex structures while preserving clarity and uniqueness in naming.

Structure and Properties

Molecular Structure

Triols consist of a hydrocarbon backbone, typically an alkane chain, substituted with three hydroxyl (-OH) groups. The arrangement of these -OH groups relative to the carbon atoms defines the molecular architecture, with possible configurations including vicinal (on adjacent carbons), geminal (two on the same carbon), or isolated (on non-adjacent carbons). This structural diversity arises from the flexibility in positioning the functional groups along the chain, influencing the molecule's overall shape and reactivity potential. For instance, vicinal triols like glycerol (propane-1,2,3-triol) feature all three -OH groups on consecutive carbons, represented by the structural formula HOCH₂CH(OH)CH₂OH.^[10]^[3] Isomerism in triols manifests primarily as constitutional isomers, where the connectivity of the -OH groups differs despite the same molecular formula. For example, butanetriols (C₄H₁₀O₃) include 1,2,3-butanetriol with vicinal -OH groups and 1,2,4-butanetriol with isolated groups at the ends. Stereoisomerism occurs when asymmetric carbons create chiral centers; propane-1,2,3-triol lacks chirality because its central carbon bears two identical -CH₂OH substituents. In contrast, longer-chain triols like 1,2,3-butanetriol possess two chiral centers at carbons 2 and 3, yielding four stereoisomers comprising two enantiomeric pairs. Geminal configurations, though less common due to potential instability, are rare in stable triols.^[10]^[11]^[12] The multiple -OH groups in triols facilitate extensive hydrogen bonding, both intramolecular and intermolecular, which dictates preferred conformations and molecular associations. Intramolecular H-bonds often stabilize gauche conformations in vicinal triols like glycerol, where the hydroxyl groups orient to form cyclic interactions. Intermolecular H-bonds create networked structures, as seen in pure glycerol where each molecule participates in approximately three such bonds, contributing to its viscous nature. In mixtures with water, glycerol's H-bonds compete with water-water interactions, forming linear glycerol-water bridges at higher concentrations that disrupt ice formation without altering the overall tetrahedral geometry.^[10]^[13]^[14]

Physical Properties

Triols exhibit high solubility in water owing to the presence of three polar hydroxyl (-OH) groups, which enable extensive hydrogen bonding with water molecules.^[15] These compounds are typically miscible with water and lower alcohols such as methanol and ethanol, reflecting their polar nature similar to that of water and simple aliphatic alcohols.^[15] However, solubility decreases in nonpolar solvents; for instance, glycerol shows only about 5% solubility by weight in acetone at room temperature.^[15] The melting and boiling points of triols are elevated compared to analogous diols, attributable to enhanced intermolecular hydrogen bonding from the additional -OH group.^[16] For example, glycerol (propane-1,2,3-triol) has a melting point of 18.17°C and a boiling point of 290°C, significantly higher than the boiling point of 197.3°C for ethylene glycol (ethane-1,2-diol).^[15]^[17] Triols generally possess densities greater than 1 g/cm³ and exhibit high viscosity at ambient temperatures, resulting from strong hydrogen-bond networks that impede molecular flow.^[16] Glycerol, for instance, has a density of 1.261 g/cm³ and a viscosity of 1.49 Pa·s at 20°C.^[15]^[18] As the carbon chain length in triols increases, overall polarity diminishes due to the growing hydrophobic alkyl portion, leading to reduced water solubility.^[16] Vicinal triols, where the -OH groups are adjacent on the carbon chain, form particularly stable hydrogen bonds, further elevating their boiling points and viscosities relative to non-vicinal isomers.^[19]

Chemical Reactivity

Triols, as polyhydric alcohols with three hydroxyl groups, exhibit reactivity characteristic of alcohols, particularly influenced by the proximity of the -OH groups in vicinal or 1,2,3-configurations. Their multiple hydroxy functionalities enable polyfunctional reactions, such as multiple esterifications or selective oxidations, often proceeding stepwise due to differences in primary and secondary alcohol reactivities. The presence of adjacent hydroxyls also facilitates intramolecular cyclizations or cleavages, distinguishing triols from monohydric alcohols. Esterification of triols occurs readily with carboxylic acids or anhydrides under acidic conditions, forming mono-, di-, or triesters depending on reaction stoichiometry and conditions. For instance, glycerol reacts with three equivalents of acetic acid in the presence of a catalyst like sulfuric acid to yield glycerol triacetate (triacetin), a common plasticizer. This reaction is reversible and equilibrium-limited, often driven forward by water removal in industrial processes using reactive distillation. Regioselectivity can be achieved enzymatically, where lipases preferentially esterify primary hydroxyls in triols. Under acidic conditions, triols undergo dehydration to form cyclic ethers, particularly from vicinal diol units. In the case of glycerol, gas-phase dehydration over zeolite catalysts like HZSM-5 at elevated temperatures (250–450°C) produces glycidol, a three-membered epoxide ring, via intramolecular loss of water from the 1,2-diol moiety. This reaction highlights the tendency of 1,2,3-triols to form strained cyclic structures, though yields depend on catalyst acidity and temperature to minimize side products like acrolein. Oxidation of triols allows selective targeting of primary versus secondary hydroxyl groups using appropriate reagents. Primary -OH groups in glycerol can be oxidized to aldehydes with mild agents, such as platinum-based catalysts under aerobic conditions, yielding glyceraldehyde without affecting the secondary -OH. Stronger oxidants like nitric acid further convert the aldehyde to carboxylic acids, forming glyceric acid. Secondary alcohols in triols oxidize to ketones, as seen in the production of dihydroxyacetone from glycerol's central -OH, underscoring the differential reactivity that enables partial oxidations for fine chemical synthesis. Periodate oxidation cleaves the carbon-carbon bonds in vicinal diol units of triols, consuming one mole of periodate (e.g., NaIO₄) per 1,2-diol linkage to produce carbonyl fragments. For 1,2,3-triols like glycerol, which contains two adjacent vicinal diol units, two moles of periodate are required, resulting in formaldehyde, formic acid, and water as products. This reaction, known as the Malaprade oxidation, proceeds rapidly in aqueous media and is widely used for structural elucidation of polyols. Triols react with aldehydes or ketones under acidic catalysis to form acetals or ketals, often cyclizing via vicinal diols to yield five- or six-membered rings. In 1,2,3-triols, the 1,2-diol unit typically forms 1,3-dioxolane rings (five-membered) with aldehydes like acetaldehyde, providing stable protecting groups in synthesis. These cyclic acetals are hydrolyzed under mild acidic conditions, reversing the protection without affecting remote functional groups.

Synthesis and Occurrence

Natural Occurrence

Triols, particularly glycerol (1,2,3-propanetriol), are ubiquitous in biological systems as essential components of lipid structures. Glycerol serves as the central backbone for triglycerides, which store energy in the form of fats in animal and plant tissues, and for phospholipids, which form the bilayer matrix of cell membranes across all domains of life.^[20] In eukaryotes and prokaryotes alike, these lipids constitute a major portion of cellular mass, with triglycerides providing insulation and energy reserves in adipose tissues of animals and seeds of plants, while phospholipids ensure membrane fluidity and integrity.^[20] The biosynthesis of glycerol occurs primarily through the reduction of dihydroxyacetone phosphate (DHAP), an intermediate in the glycolytic pathway, to glycerol-3-phosphate, catalyzed by the enzyme glycerol-3-phosphate dehydrogenase using NADH as a cofactor. This process is conserved across organisms, linking glycerol production to central carbon metabolism and enabling rapid accumulation under osmotic stress or during lipid synthesis. In yeast and mammalian cells, this pathway supports the formation of glycerolipids, with glycerol-3-phosphate subsequently acylated to yield phosphatidic acid, a precursor to both triglycerides and phospholipids.^[21] Beyond glycerol, other triols occur naturally in microbial systems, often as components of specialized lipids. For instance, 1,2,3-butanetriol is incorporated into butanetriol dialkyl glycerol tetraethers (BDGTs), unusual membrane lipids identified in archaea from estuarine and deep-sea sediments, where they may enhance membrane stability in extreme environments. These structures suggest an adaptive role in polyol-based lipid diversity among ancient microbial lineages. Related polyols, such as inositol (a cyclohexanehexol), are also prevalent in biological membranes and signaling pathways, though they extend beyond triol functionality as cyclic sugar alcohols found in plants, animals, and microbes.^[22]^[23]^[24] In environmental contexts, triols like glycerol are integral to plant oils and animal fats, where they form the esterified core of triacylglycerols that dominate lipid composition in seeds, fruits, and adipose depots. Additionally, microbial fermentation in anaerobic conditions yields free glycerol as a byproduct, observed in processes by osmotolerant yeasts and bacteria such as Saccharomyces and Escherichia species, contributing to natural glycerol pools in soils, sediments, and fermented plant materials.^[25]

Synthetic Methods

Triols, compounds featuring three hydroxyl groups on a hydrocarbon chain, are synthesized through various laboratory and industrial techniques, with glycerol (1,2,3-propanetriol) serving as a prototypical example due to its structural simplicity and commercial relevance.^[26] In laboratory settings, one common approach involves the reduction of trioses, such as dihydroxyacetone, to the corresponding triol. For instance, dihydroxyacetone is reduced to glycerol using sodium borohydride (NaBH₄) in aqueous or methanolic solution at room temperature, yielding the product in high efficiency with minimal side products. This method leverages the selective hydride transfer to the carbonyl group, preserving the existing hydroxyl functionalities. Another classical laboratory method is the hydrolysis of polyhalides. Treatment of 1,2,3-trihalopropanes, like 1,2,3-trichloropropane, with aqueous base (e.g., NaOH) under heating leads to sequential nucleophilic substitutions, displacing halogens with hydroxyl groups to form glycerol. This stepwise dehalogenation typically proceeds via intermediate dihalohydrins and requires controlled conditions to avoid over-alkalinity.^[27] Industrial production of glycerol historically relies on petrochemical routes starting from propylene. The process begins with the chlorination of propylene to allyl chloride at elevated temperatures (around 500°C), followed by hypochlorination to form dichlorohydrin, cyclization to epichlorohydrin, and final alkaline hydrolysis to glycerol. This multi-step sequence achieves high yields (over 90%) and has been a cornerstone of large-scale triol synthesis since the mid-20th century.^[26] In recent decades, bio-based methods have dominated, with glycerol emerging as a major byproduct of biodiesel production. During the transesterification of triglycerides from vegetable oils or animal fats with methanol, approximately 10% by weight of the feedstock is converted to crude glycerol, which is then purified via distillation and ion exchange for industrial use. This sustainable route has significantly increased global glycerol supply, reducing reliance on synthetic propylene pathways.^[28] Contemporary advancements include catalytic hydrogenation of glyceraldehyde to glycerol, employing metal catalysts like ruthenium or nickel under mild hydrogen pressure (e.g., 50 bar, 100°C), offering high selectivity (>95%) and compatibility with renewable feedstocks. Enzymatic methods further enable precise synthesis; for example, aldose reductases or glycerol dehydrogenases, often cofactor-recycled with NADH, reduce glyceraldehyde to glycerol in aqueous media at ambient conditions, achieving enantiopure products. These biocatalytic routes using lipases for regioselective modifications complement reduction steps in multi-enzyme cascades.

Notable Examples

Glycerol

Glycerol, systematically named propane-1,2,3-triol, is a simple triol with the molecular formula C₃H₈O₃ and the structural formula HOCH₂CH(OH)CH₂OH.^[29]^[3] It represents the prototypical example of a triol, featuring three hydroxyl groups attached to a three-carbon chain, which aligns with the general nomenclature for such compounds as alkane-x,y,z-triols.^[29] Glycerol was first isolated in 1779 by Swedish chemist Carl Wilhelm Scheele from the saponification of fats and oils, initially obtained by heating these substances with lead oxide.^[30] In 1811, French chemist Michel Eugène Chevreul provided a more detailed description and coined the name "glycerin" (from Greek glykeros, meaning sweet), recognizing its distinct properties separate from the fatty acids produced in the process.^[30] This discovery laid the foundation for understanding triols as components of natural lipids. Glycerol exhibits several unique physical properties that distinguish it among triols: it is a colorless, odorless, viscous liquid that is hygroscopic, readily absorbing moisture from the air due to its multiple hydroxyl groups.^[3] It has a sweet taste and is non-toxic, allowing safe ingestion in small amounts, which contributes to its wide recognition as a safe substance.^[31] Additionally, its ability to lower the freezing point of water solutions makes it an effective cryoprotectant, preventing ice crystal formation in biological samples during storage.^[32] Regarding isomerism, glycerol is achiral and possesses no stereoisomers because its molecular structure includes a plane of symmetry passing through the central carbon atom and the hydrogen attached to it, rendering the two terminal -CH₂OH groups identical.^[33] This symmetry eliminates optical activity, unlike triols with asymmetric substitutions that could exhibit chirality.

Other Common Triols

1,2,6-Hexanetriol is a linear aliphatic triol with the molecular formula C₆H₁₄O₃ and structure HOCH₂CH(OH)(CH₂)₄OH, featuring two primary hydroxyl groups and one secondary hydroxyl group, where the hydroxyls at positions 1 and 2 are vicinal while the one at position 6 is separated by a (CH₂)₃ chain.^[9] This configuration imparts flexibility and reduced hydrogen bonding compared to more clustered polyols, making it suitable as a polyol intermediate in polymer chemistry, particularly for synthesizing alkyd resins with improved properties such as reduced gelation tendency.^[34] 1,1,1-Tris(hydroxymethyl)ethane, also known as trimethylolethane, is a branched triol with the formula CH₃C(CH₂OH)₃ (C₅H₁₂O₃), characterized by a central quaternary carbon bearing a methyl group and three primary hydroxymethyl arms in a geminal arrangement.^[35] Its compact, tripod-like structure enables high functionality in condensation reactions, serving as a key cross-linking agent in the production of alkyd and polyester resins, as well as powder coatings, where it enhances durability and weather resistance.^[36] Trimethylolpropane (TMP), or 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, is a branched aliphatic triol with the formula (HOCH₂)₃CCH₂CH₃ (C₆H₁₄O₃), featuring a neopentyl-like core with three primary hydroxyl groups.^[37] It serves as a cross-linking agent in polyurethane and polyester resins, improving mechanical properties in coatings, adhesives, and lubricants.^[4] Phloroglucinol, or 1,3,5-trihydroxybenzene, is an aromatic triol with the formula C₆H₃(OH)₃ (C₆H₆O₃), consisting of a benzene ring symmetrically substituted with three hydroxyl groups at the meta positions.^[38] This symmetric arrangement facilitates its role as a fundamental building block in phlorotannins, oligomeric polyphenols found in brown algae, where it polymerizes via ether and C-C linkages to form complex structures with antioxidant properties.^[39] Additionally, phloroglucinol acts as a coupling agent in the synthesis of azo dyes, particularly fast black shades for textiles and hair colorants, due to its reactivity with diazonium salts.^[40] Pyrogallol, or benzene-1,2,3-triol, is an aromatic triol with the formula C₆H₃(OH)₃ (C₆H₆O₃), featuring three adjacent hydroxyl groups on a benzene ring. It is used in photography as a developing agent, in hair dyes, and in the synthesis of antioxidants due to its redox properties.^[5] Cyclohexanetriols represent cyclic aliphatic triols derived from cyclohexane with three hydroxyl groups, existing in stereoisomeric forms such as 1,2,3-, 1,2,4-, and 1,3,5-cyclohexanetriol (all C₆H₁₂O₃).^[41] The 1,3,5-isomer, with its symmetric equatorial hydroxyl arrangement in the chair conformation, serves as a versatile scaffold in organic synthesis, analogous to reduced forms of inositol but with fewer hydroxyls for targeted functionalization.^[42] These compounds are employed as chiral starting materials in the preparation of pharmaceutical intermediates, including vitamin D analogues and prostacyclin precursors like Corey lactone, leveraging their rigid cyclic structure for stereocontrol.^[43]

Applications and Uses

Biological Roles

Glycerol, the most prominent triol in biological systems, serves as a crucial intermediate in metabolic pathways, particularly in the liver and other tissues. In gluconeogenesis, glycerol derived from lipid breakdown is converted into glucose through a series of enzymatic steps, providing an essential source of energy during fasting or low-carbohydrate states.^[44] This process positions glycerol at the intersection of lipid and carbohydrate metabolism, allowing for efficient recycling of carbon skeletons from stored fats.^[45] Additionally, glycerol is rapidly phosphorylated to form glycerol-3-phosphate, which acts as a key precursor in the biosynthesis of glycerolipids, including the esterification of fatty acids to produce complex lipids.^[46] Structurally, glycerol forms the central backbone of triglycerides, neutral lipids that store energy in adipose tissue and serve as a major reservoir for long-term energy needs in animals.^[20] These molecules consist of one glycerol unit esterified with three fatty acids, enabling compact and hydrophobic storage within lipid droplets. In cell membranes, glycerol is integral to phospholipids, where it links two hydrophobic fatty acid tails to a hydrophilic head group, contributing to the bilayer architecture that maintains cellular integrity and regulates permeability.^[47] The composition of these phospholipids, influenced by glycerol's role, helps modulate membrane fluidity, allowing adaptation to varying environmental temperatures and ensuring proper function of membrane-bound proteins.^[48] Glycerol also functions in osmoregulation as a compatible solute in select organisms. In certain microorganisms, such as Antarctic species of Chlamydomonas, it accumulates intracellularly to counteract osmotic stress from high salinity or dehydration without disrupting enzymatic activity.^[49] Similarly, in cold-adapted fish like the rainbow smelt (Osmerus mordax), glycerol is produced and stored in high concentrations in plasma, liver, and muscle tissues to lower the freezing point of bodily fluids, acting as a natural antifreeze to enable survival in subzero waters.^[50] The initial step in glycerol's metabolic utilization is catalyzed by glycerol kinase, an enzyme that phosphorylates free glycerol using ATP to yield glycerol-3-phosphate and ADP.^[51] This ATP-dependent reaction is rate-limiting and occurs primarily in the liver, kidney, and intestine, regulating glycerol influx into catabolic and anabolic pathways while preventing toxic accumulation.^[52]

Industrial Applications

Triols, particularly glycerol, serve as versatile humectants in various industrial sectors due to their ability to retain moisture. In cosmetics and personal care products, glycerol is commonly incorporated at concentrations of 5-20% in lotions and creams to prevent drying and enhance skin hydration.^[53] In the food industry, it functions as a humectant and sweetener in products like confectionery and baked goods, maintaining softness and texture.^[3] Additionally, glycerol is used in tobacco processing to retain moisture and improve handling properties. In polymer manufacturing, glycerol acts as a key polyol component. It is essential in the production of polyurethane foams, where it contributes to cross-linking and flexibility in rigid and flexible variants used for insulation and cushioning.^[54] Glycerol also serves as a building block in alkyd resins, which are widely employed in paints, coatings, and varnishes for their durability and adhesion. Other triols, such as 1,2,6-hexanetriol, are utilized as crosslinkers in polyurethane and polyester formulations to enhance mechanical strength.^[55] Glycerol finds significant application in the pharmaceutical sector as a solvent and vehicle in liquid formulations. It is a common ingredient in cough syrups, where it not only dissolves active components but also provides a soothing effect on the throat.^[56] Furthermore, glycerol is a precursor to nitroglycerin, synthesized via nitration, which is then used in dynamite as a stable explosive for mining and construction.^[57] As a major byproduct of biodiesel production through transesterification of vegetable oils or animal fats, glycerol constitutes approximately 10% by weight of the output, presenting both a challenge and opportunity for valorization.^[58] Refined glycerol from this process is repurposed in antifreeze formulations for its low freezing point and non-toxicity compared to ethylene glycol.^[59] It is also a primary component in e-cigarette liquids, often comprising 20-50% of the mixture alongside propylene glycol to generate vapor.^[60] In the 2020s, emerging applications of glycerol emphasize sustainability, including its conversion into biofuels such as bioethanol via microbial fermentation, addressing excess supply from biodiesel expansion.^[58] Additionally, glycerol is gaining traction as a green solvent in organic synthesis and extraction processes, offering biodegradability and low toxicity as alternatives to petroleum-based solvents.^[61]

References

[1]
TRIOL Definition & Meaning - Merriam-Webster
The meaning of TRIOL is a chemical compound (such as glycerol) containing three hydroxyl groups.
[2]
-triol - (Intro to Chemistry) - Vocab, Definition, Explanations | Fiveable
Definition. A -triol is a compound that contains three hydroxyl (-OH) functional groups attached to a carbon chain or ring structure.
[3]
Glycerol | C3H8O3 | CID 753 - PubChem - NIH
Glycerol is a triol with a structure of propane substituted at positions 1, 2 and 3 by hydroxy groups. It has a role as an osmolyte, a solvent, a detergent, ...
[4]
Triol - an overview | ScienceDirect Topics
A triol is defined as a compound that results from the reaction of a trifunctional initiator containing three active hydrogen atoms with organic oxides, leading ...
[5]
Benzene-1,2,3-triol Applications: From Photography to Cosmetics
Oct 27, 2025 · Explore the diverse uses of Benzene-1,2,3-triol (Pyrogallol) in photography, hair dyes, and synthesis. Find quality suppliers and understand ...<|control11|><|separator|>
[6]
Illustrated Glossary of Organic Chemistry - Triol
Triol: A molecule having three hydroxyl groups. Example Triols. 1,2,3-Propanetriol (glycerin), (D)-2-Deoxyribose. Related terms: Glycol, triose, tricyclic.
[7]
TRIOL definition in American English - Collins Dictionary
triol in American English (ˈtraiɔl, -ɑl) noun. Chemistry. a compound having three hydroxyl groups. Word origin.
[8]
Glycerol - American Chemical Society
Apr 15, 2024 · Glycerol is the simplest alkane triol. It was historically called glycerine (or glycerin), but that name is misleading because the -ine suffix denotes an amine ...
[9]
1,2,6-Hexanetriol | C6H14O3 | CID 7823 - PubChem
1,2,6-Hexanetriol | C6H14O3 | CID 7823 - structure, chemical names, physical and chemical properties, classification, patents, literature, ...
[10]
Triol - an overview | ScienceDirect Topics
4.2 for chemical structure of glycerol). It is used across thousands of applications including food and pharmaceutical industries [48].
[11]
1,2,4-Butanetriol | C4H10O3 | CID 18302 - PubChem - NIH
1,2,4-butanetriol is a triol that is butane carrying three hydroxy substituents at position 1, 2 and 4. It has a role as a bacterial xenobiotic metabolite ...
[12]
Solved 1,2,3-Butanetriol has two stereocenters (carbons 2 - Chegg
Sep 18, 2021 · 1,2,3-Butanetriol has two stereocenters, thus 2^2 = 4 stereoisomers are possible. Enantiomers are mirror images, diastereomers are not.
[13]
[PDF] Effect of pressure on hydrogen bonding in glycerol
Crystalline glycerol is fully hydrogen bonded, with each molecule participating ~as donor! in exactly three hydrogen bonds.17 In the liquid each molecule ...
[14]
Hydrogen bonding and the cryoprotective properties of glycerol ...
Glycerol-glycerol hydrogen bonds become the dominant interaction in the first hydration shell, and the percolation nature of the water network is disturbed. At ...
[15]
[PDF] Physical Properties of Glycerine and its Solutions
Glycerine is viscous, stable, hygroscopic, widely compatible, clear, odorless, safe, prevents freezing, and promotes long shelf life.Missing: triols | Show results with:triols
[16]
13.3: Physical Properties of Alcohols - Chemistry LibreTexts
May 30, 2020 · Alcohols' boiling points increase with carbon atoms due to hydrogen bonding. Small alcohols are soluble in water, but solubility decreases with ...
[17]
14.6: Glycols and Glycerol - Chemistry LibreTexts
Sep 15, 2022 · This results in a high boiling point—198°C; thus ethylene glycol does not boil away when it is used as an antifreeze. It is also completely ...
[18]
Alcohols and Carboxylic Acids - Physical Data
The data includes molweight, melting and boiling points, density, pKa-values, and number of carbon and hydrogen atoms for 150 alcohols and acids.
[19]
Hydrogen bonding in strained cyclic vicinal diols - ScienceDirect.com
Certain strained cyclic vicinal diols, in which the C–O bonds are syn-periplanar or planar, form an intramolecular hydrogen bond with a (3, −1) bond critical ...
[20]
Biochemistry, Lipids - StatPearls - NCBI Bookshelf - NIH
May 1, 2023 · The structure is typically made of a glycerol backbone ... The structure of lipoprotein consists of triglycerides, cholesterol, phospholipids, and ...
[21]
The glycerol backbone of phospholipids derives from ...
May 29, 2018 · Glycerol phosphate not only forms the backbone of triglycerides but is also needed for the biosynthesis of glycerophospholipids (GPL), the ...Results · Fig. 1 · Fig. 3
[22]
Structural elucidation and environmental distributions of butanetriol ...
Jan 22, 2020 · The specific 1,2,3 butanetriol structure of their backbone could then be interpreted as an adaptive trait of sedimentary Archaea to energy ...
[23]
Identification of unusual butanetriol dialkyl glycerol tetraether and ...
Dec 27, 2013 · Here, we provide three lines of evidence to confirm the existence of unusual tetraether lipids with 1,2,3-butanetriol as one of the two termini ...
[24]
Inositol - an overview | ScienceDirect Topics
Inositol: Early characterization in plants Inositol is a naturally occurring cyclic polyol. Its discovery dates back to mid-1800s by Scherer, who isolated the ...
[25]
Glycerol production by microbial fermentation: A review
Glycerol can be produced either by microbial fermentation or by chemical synthesis from petrochemical feedstocks or can be recovered as a by-product of soap ...
[26]
Glycerol Production and Transformation: A Critical Review with ... - NIH
Glycerol can be produced by using different processes and feedstocks. For example, it can be obtained by propylene synthesis via several pathways [8], by ...
[27]
Electrochemical Reduction of the Simplest Monosaccharides
Nov 16, 2020 · with NaBH4, however, dihydroxyacetone yielded glycerol. The difference between the chem. and electrochem. redn. of dihydroxyacetone was ...
[28]
1,2,3-Trichloropropane - an overview | ScienceDirect Topics
The production of glycerol from epichlorohydrin involves: Low pressure alkaline hydrolysis of ECH at 80-200°C with a 10–15 % aqueous solution of sodium ...
[29]
Homologation of Boronic Esters with Lithiated Epoxides for the ...
Lithiated epoxides react stereospecifically with boronic esters to give syn-1,2-diols, a process that can be used iteratively to create triols containing four ...
[30]
Purified Glycerine from Biodiesel Production as Biomass or Waste ...
Jun 23, 2023 · It is a by-product of the transesterification of triglycerides, such as animal fats, vegetable oils, or used cooking oils during the biodiesel ...
[31]
Enzymatic Production of Glycerol from Glycolaldehyde and ...
May 9, 2024 · Glycerol is produced using a one-pot cascade reaction with FSA and ALR, converting formaldehyde and glycolaldehyde to L-glyceraldehyde, then to ...
[32]
Glycerol - Registration Dossier - ECHA
Molecular formula: C3H8O3; IUPAC Name: propane-1,2,3-triol. glycerol. State Form: liquid. Constituent 1. Chemical structure. Reference substance name: Glycerol ...
[33]
Glycerol - an overview | ScienceDirect Topics
The process can be divided into hydrogenolysis, oxidation, acid-catalyzed dehydration, etherification, and pyrolysis synthesis according to the reaction type ...
[34]
Glycerol | 56-81-5 - ChemicalBook
Glycerol has been recognized as a non-toxic and safe substance with no harmful ... Glycerol's hygroscopic properties make it a good moisturizer in skin products.<|separator|>
[35]
Glycerol - an overview | ScienceDirect Topics
Because GLY is less toxic to peritoneal cells than glucose, it is also used in peritoneal dialysis fluid. As such it is an effective osmotic agent without ...
[36]
chapter 4 - Organic Chemistry
A meso compound has multiple chiral centers but, because it has a plane of symmetry, is achiral. ... The correct answer is glycerol. Exercise 4.4.1 (a) is ...<|control11|><|separator|>
[37]
US2768213A - 1, 2, 6-hexanetriol - Google Patents
As a chemical intermediate 1,2,6-hexanetriol also is useful for the preparation of alkyd resins, for which use its freedom from tendency to form undesirable ...
[38]
Trimethylolethane | C5H12O3 | CID 6502 - PubChem - NIH
1,1,1-Tris(hydroxymethyl)ethane's production and use in the manufacture of varnishes, alkyd and polyester resins, as a conditioning agent and synthetic drying ...
[39]
https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/phloroglucinol
[40]
Phloroglucinol | C6H6O3 | CID 359 - PubChem - NIH
Phloroglucinol is a benzenetriol with hydroxy groups at position 1, 3 and 5. It has a role as an algal metabolite. It is a phenolic donor and a benzenetriol.
[41]
Phloroglucinol - an overview | ScienceDirect Topics
Phloroglucinol is a polyphenolic compound that chemical structure includes an aromatic phenyl ring with three hydroxyl groups (Fig. 1a).
[42]
Phloroglucinol 99.3% Anhydrous - APC Pure
14-day returnsIt is also used in the study of condensed tannins through depolymerisation. ... Functions as a coupling agent, particularly in the production of fast black dyes ...
[43]
Cyclohexane-1,2,3-triol | C6H12O3 | CID 222962 - PubChem
Sep 13, 2025 · Cyclohexane-1,2,3-triol | C6H12O3 | CID 222962 - structure, chemical names, physical and chemical properties, classification, patents, ...
[44]
Pot and time economies in the total synthesis of Corey lactone
Dec 23, 2019 · Woodward reported an innovative 11 step racemic synthesis starting from cis-cyclohexane-1,3,5-triol via rearrangement. The chiral Corey ...
[45]
Multiselective enzymatic reactions for the synthesis of protected ...
In the context of the synthesis of vitamin D analogues we should mention Huang et al.,4 who started an approach from cis-cyclohexane-1,3,5-triol which was ...Missing: significance | Show results with:significance
[46]
Physiology, Gluconeogenesis - StatPearls - NCBI Bookshelf - NIH
Nov 13, 2023 · Gluconeogenesis is the process that allows the body to form glucose from non-hexose precursors, particularly glycerol, lactate, pyruvate, propionate, and ...
[47]
Glycerol metabolism regulates gluconeogenesis - RUcore
Glycerol stands at the crossroads of lipid and glucose metabolism as it is not only the preferred substrate for GNG but also the backbone for free fatty acid re ...
[48]
Lipid Metabolism - PMC - NIH
Fatty acid synthase (FASN) converts acetyl-CoA to palmitate, which, together with glycerol 3-phosphate, generates lipids, such as triglycerides and ...Glycolysis And Mitochondrial... · Figure 4 · Lipid Catabolism Generates...
[49]
The Lipid Bilayer - Molecular Biology of the Cell - NCBI Bookshelf
The lipid bilayer has been firmly established as the universal basis for cell-membrane structure. It is easily seen by electron microscopy.Missing: triglycerides | Show results with:triglycerides
[50]
The role of phospholipid molecular species in determining the ... - NIH
Besides serving as general membrane 'building blocks', glycerophospholipids play an important role in determining the physical properties of the membrane, which ...
[51]
Glycerol Is an Osmoprotectant in Two Antarctic Chlamydomonas ...
Aug 20, 2020 · Glycerol, a compatible solute, has previously been found to act as an osmoprotectant in some marine Chlamydomonas species and several species of ...
[52]
Thermal acclimation in rainbow smelt, Osmerus mordax, leads to ...
Jan 31, 2013 · These fish express both anti-freeze proteins and glycerol in their plasma, liver, muscle and other tissues to avoid freezing at sub-zero ...
[53]
2710 - Gene ResultGK glycerol kinase [ (human)] - NCBI
Sep 9, 2025 · This protein is a key enzyme in the regulation of glycerol uptake and metabolism. It catalyzes the phosphorylation of glycerol by ATP, yielding ADP and ...
[54]
https://pubs.acs.org/doi/10.1021/acs.macromol.5c00383
[55]
Safety Assessment of Glycerin as Used in Cosmetics - Sage Journals
Dec 16, 2019 · Glycerin is reported to be used at concentrations up to 79.2% in leave-on products, 99.4% in rinse-off products, and 47.9% in products diluted ...
[56]
Development of Biodegradable and Biobased Poly(glycerol ...
Sep 10, 2025 · Fully biobased oligomers were synthesized from glycerol, levulinic acid, and malonic acid via melt polycondensation.
[57]
1,2,6-Hexanetriol, 96% - Fisher Scientific
It acts as wetting agent of tobacco and special hydraulic fluid. It is used in the production of alkyd resins, celluloid, polyurethane and synthetic rubber.
[58]
Soothing Properties of Glycerol in Cough Syrups for Acute ... - NIH
Jan 20, 2017 · Glycerol is a component in most cough syrups. It is often thought of only as a solvent or thickening agent; however, it also contributes to the ...
[59]
Nitroglycerine and Dynamite - NobelPrize.org
Nitroglycerine is an explosive liquid which was first made by Ascanio Sobrero in 1846 by treating glycerol with a mixture of nitric and sulphuric acid.
[60]
Glycerol waste to value added products and its potential applications
Jun 7, 2021 · This review focuses on the significance of crude glycerol in the value-added utilisation and conversion to bioethanol by a fermentation process
[61]
Glycerin in Antifreeze - ASTM
Glycerin, which is nontoxic to the environment, was used as a heat transfer agent in antifreeze formulations as early as 1920, it was eventually replaced by ...
[62]
Toxicology of E-Cigarette Constituents - NCBI - NIH
PG and glycerol (commonly referred to as a “vegetable glycerin” in liquid formulations) are the most common vaporizing solvents used in e-cigarettes. Hutzler ...
[63]
(PDF) Recent Advances in the Use of Glycerol as Green Solvent for ...
Aug 8, 2025 · In this account, we highlight some of our progress made over the last 10 years towards the development of green methodologies. We investigated ...