Pyridoxine (65-23-6) Physical and Chemical Properties
Pyridoxine
Water‑soluble vitamin B6 analogue supplied as an API/nutritional raw material for pharmaceutical, nutraceutical and research applications.
| CAS Number | 65-23-6 |
| Family | Vitamin B6 analogs (pyridines) |
| Typical Form | White crystalline powder |
| Common Grades | BP, EP, FCC, JP |
Pyridoxine is a substituted pyridine (a hydroxymethylpyridine) belonging to the vitamin B6 structural class. The molecule comprises a methyl-substituted pyridine ring bearing a phenolic hydroxy group and two hydroxymethyl substituents, giving the neutral free base the empirical composition \(\ce{C8H11NO3}\). Electronically, the ring oxygen- and nitrogen-containing substituents create a moderately polar, hydrogen-bonding scaffold: the compound presents multiple hydrogen-bond donors and acceptors and a relatively low lipophilicity for a heteroaromatic system.
Functionally, pyridoxine is water-soluble and chemically behaves as a neutral, polar organic base with a phenolic OH that can participate in hydrogen bonding and undergo enzymatic oxidation/phosphorylation in biological systems. It is prodrug-like in physiological contexts: metabolic conversion in the liver produces phosphorylated and oxidized derivatives (notably pyridoxal 5'-phosphate) that serve as essential coenzymes. Chemically, the free base is stable as a crystalline solid under normal laboratory conditions but is susceptible to standard oxidative and photochemical transformations of substituted pyridines under forcing conditions.
Pyridoxine has broad pharmaceutical and nutritional relevance as a vitamin B6 form used therapeutically to treat deficiency and to prevent specific drug-induced neuropathies; it is also incorporated in dietary supplements and fortified foods. Common commercial grades reported for this substance include: BP, EP, FCC, JP.
Basic Physicochemical Properties
Density and Solid-State Form
No experimentally established value for this property is available in the current data context.
Melting Point
Experimental melting point reported as 159-162 \(\,^\circ\mathrm{C}\).
Solubility and Dissolution Behavior
Solubility entries include the values "220000" and "79 mg/mL" (reported value). The frequently cited experimental aqueous/solvent solubility is given as 79 \(\mathrm{mg}\,\mathrm{mL}^{-1}\), consistent with a highly water-soluble B‑vitamin derivative; this high solubility reflects the two hydroxymethyl groups and the phenolic hydroxyl that promote hydration and hydrogen-bonded solvation. Vapor pressure is very low (0.00000028 [mmHg]) consistent with a non-volatile crystalline solid.
Chemical Properties
Acid–Base Behavior and Qualitative pKa
No experimentally established value for this property is available in the current data context.
(Qualitative) The molecule contains a phenolic hydroxy group on the pyridine ring and a basic pyridine nitrogen. In practice, pyridoxine exists predominantly as the neutral free base under near‑neutral aqueous conditions; the pyridine nitrogen can be protonated under strongly acidic conditions and the phenolic OH can act as a weak Brønsted acid. The compound’s high polarity and multiple hydrogen-bonding sites govern its aqueous speciation and interactions with proteins and enzymes rather than strong acid–base behavior in the physiological pH range.
Reactivity and Stability
Pyridoxine is chemically stable as a dry crystalline solid but can undergo oxidation and enzymatic transformation under biological conditions (conversion to pyridoxal and then phosphorylation to biologically active pyridoxal 5'-phosphate). It is water‑soluble and generally stable in neutral aqueous media but can be susceptible to oxidative degradation and photochemical reactions typical of substituted pyridines and phenolic compounds. The presence of multiple hydroxyl functions enhances susceptibility to esterification or derivatization under appropriate synthetic conditions.
Molecular Parameters
Molecular Weight and Formula
Molecular formula: \(\ce{C8H11NO3}\)
Molecular weight (reported): 169.18
Additional computed identifiers and descriptors include exact/monoisotopic mass 169.07389321, topological polar surface area 73.6, hydrogen-bond donor count 3, hydrogen-bond acceptor count 4, rotatable bond count 2, and formal charge 0.
LogP and Structural Features
Reported partitioning descriptors: XLogP = -0.8 and LogP = -0.77 (experimental/computed entries given). The negative LogP values reflect low lipophilicity driven by three hydroxyl-type functionalities and a polar heteroaromatic core; this underpins high aqueous solubility and low membrane partitioning relative to more lipophilic heterocycles.
Structural Identifiers (SMILES, InChI)
SMILES: CC1=NC=C(C(=C1O)CO)CO
InChI: InChI=1S/C8H11NO3/c1-5-8(12)7(4-11)6(3-10)2-9-5/h2,10-12H,3-4H2,1H3
InChIKey: LXNHXLLTXMVWPM-UHFFFAOYSA-N
Identifiers and Synonyms
Registry Numbers and Codes
CAS number: 65-23-6
EC number: 200-603-0
UNII: KV2JZ1BI6Z
ChEBI: CHEBI:16709
ChEMBL: CHEMBL1364
DrugBank: DB00165
HMDB: HMDB0000239
KEGG: C00314 / D08454
Synonyms and Brand-Independent Names
Common synonyms and systematic names (selected):
- Pyridoxine
- Pyridoxol
- Pyridoxin
- 4,5-bis(hydroxymethyl)-2-methylpyridin-3-ol
- 3-hydroxy-4,5-bis(hydroxymethyl)-2-methylpyridine
- Adermine
- Gravidox
- Vitamin B6 (one of the vitamers)
(Additional depositor-supplied synonyms and historical names are recorded in supplier and regulatory listings.)
Industrial and Pharmaceutical Applications
Role as Active Ingredient or Intermediate
Pyridoxine functions pharmaceutically as an active vitamin B6 form used to treat vitamin B6 deficiency and to prevent peripheral neuropathy associated with certain drug therapies. In biological systems it is a precursor that is enzymatically converted to pyridoxal 5'-phosphate, the active coenzyme required for numerous aminotransferase and decarboxylase reactions. Industrially it is used in dietary supplements, fortified foods, and pharmaceutical formulations as the free base or as salts (e.g., hydrochloride).
Formulation and Development Contexts
Pharmaceutical formulations commonly use pyridoxine in oral solid dosage forms; the hydrochloride salt is a frequently used, more hygroscopic/soluble form (related CAS reported for hydrochloride: 58-56-0). Development considerations focus on moisture control, stabilization against oxidation/light, and appropriate excipient selection to preserve the active vitamer and enable reliable dissolution given the high aqueous solubility. The WHO essential medicines listing notes oral solid formulations (25 mg hydrochloride) for therapeutic use.
Specifications and Grades
Typical Grade Types (Pharmaceutical, Analytical, Technical)
Typical commercial grade concepts applicable to pyridoxine include pharmaceutical (pharmacopeial) grade for use in medicinal products, analytical grade for laboratory/assay work, and technical or food-grade for fortification and feed applications. The substance is supplied in various pharmacopeial grades consistent with the indicated commercial grade strings.
Reported commercial grades: BP, EP, FCC, JP.
General Quality Attributes (Qualitative Description)
Quality attributes that commonly distinguish grades are purity (assay), residual solvents, polymorphic/physical form, residual inorganic salts, and microbiological limits for grades intended for food or pharmaceutical use. Pharmaceutical-grade material is typically specified with analytical documentation (identity, assay, impurity profile, and moisture content) and controls for oxidative degradation; food/fcc grades emphasize suitability for food fortification and compliance with additive specifications.
Safety and Handling Overview
Toxicological Profile and Exposure Considerations
Pyridoxine is an essential nutrient at physiological doses but can be toxic at substantially higher intakes. Acute oral LD50 reported: 4 gm/kg (rat). Chronic ingestion of gram‑level quantities has been associated with sensory neuropathy and ataxia in humans and testicular toxicity in rodent studies; adverse neurological effects are the principal concern for overdose. Reported hazard classifications emphasize irritation: skin irritation, serious eye irritation, and potential respiratory tract irritation in occupational exposures. For medicinal dosing, safety margins are established clinically; for manufacturing and handling, inhalation and dermal exposure control is prudent.
Storage and Handling Guidelines
Store dry, in a cool, well‑ventilated area protected from light and strong oxidants. Avoid dust generation; use local exhaust ventilation for powder handling. Recommended protective measures include nitrile or compatible gloves, eye protection, and respiratory protection where dust/aerosols may occur. Prevent contamination of foodstuffs and maintain good industrial hygiene. For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
