Cyanocobalamin (Vitamin B12) (68-19-9) Physical and Chemical Properties

Chemical Profile

Cyanocobalamin (Vitamin B12)

A water‑soluble cobalamin supplied as a crystalline vitamin B12 derivative for use as an active ingredient, analytical reference, or process input in pharmaceutical and nutraceutical manufacturing.

CAS Number	68-19-9
Family	Cobalamins (corrinoid vitamin)
Typical Form	Powder or crystalline solid
Common Grades	EP

Commonly used by formulation and R&D teams as an API or reference standard in supplement and pharmaceutical production; quality control focuses on assay, impurity profile and stability. Handle and store in light‑protected, controlled conditions to limit photodegradation and support consistent batch-to-batch performance.

Cyanocobalamin is a cobalamin-class corrin macrocycle: a cobalt-centered porphyrinoid-like corrin ring bearing multiple amide-containing side chains, a nucleotide (5,6-dimethylbenzimidazole) axial ligand via the lower (base) coordination site and a cyanide axial ligand in the upper (β) position. Structurally it combines a large, highly substituted tetrapyrrolic corrin core with a phosphorylated ribose moiety and multiple pendant carboxamide and aminoalkyl substituents; the molecular architecture produces a rigid metal-centered complex with extensive hydrogen-bonding capacity and a defined three-dimensional stereochemistry (numerous stereocenters and double-bond stereochemistry within the corrin periphery).

Electronically, the cobalt center is in a high oxidation-state coordination environment (formally Co(III) in the cyanide complex) and the ligand field is dominated by the corrin π-system and strong-field axial ligands. The molecule is formally neutral as an isolated compound, but contains a localized metal cation balanced by ligand anionic contributions within the covalent assembly. Because of the high number of polar functional groups (amide carbonyls, primary/secondary amines, phosphate ester, hydroxyls) and the large topological polar surface area, cyanocobalamin is highly polar and strongly hydrated in aqueous environments; it is effectively water-soluble and displays low intrinsic lipophilicity compared with small organic cofactors of comparable mass.

Chemically and pharmaceutically, cyanocobalamin is widely used as a stable, administrable form of vitamin B12 that can be converted enzymatically or chemically into metabolically active cobalamin cofactors (methylcobalamin and adenosylcobalamin). It is widely relevant in clinical nutrition and biochemical research as a vitamin supplement and as a precursor for cellular B12-dependent processes.

Common commercial grades reported for this substance include: EP.

Molecular Overview

Molecular Weight and Composition

Molecular formula: \(\ce{C63H88CoN14O14P}\).
Molecular weight: 1355.4 Da (reported value: 1355.4).
Exact mass / Monoisotopic mass: 1354.567399 (reported value: 1354.567399).
Topological polar surface area (TPSA): 476 \(\mathrm{\AA}^2\) (reported value: 476).
Heavy atom count: 93 (reported value: 93).
Defined atom stereocenter count: 14 (reported value: 14).
Defined bond stereocenter count: 3 (reported value: 3).
Covalently-bonded unit count: 3 (reported value: 3) — reflects the combined representation of the corrin cobalt complex with its countercomponents in some depictions.
Hydrogen-bond donor count: 9 (reported value: 9).
Hydrogen-bond acceptor count: 21 (reported value: 21).
Rotatable bond count: 26 (reported value: 26).
Formal charge: 0 (reported value: 0).
Molecular complexity: 3150 (reported value: 3150).
Collision cross section (experimental): 338.2 \(\mathrm{\AA}^2\) [M+H]+ [CCS Type: DT; Method: single field calibrated with Agilent tune mix (Agilent)] (reported value: 338.2 Å² [M+H]+ [CCS Type: DT; Method: single field calibrated with Agilent tune mix (Agilent)]).

Note on 3D modelling: conformer generation for this compound is frequently disallowed in common small-molecule force-field workflows because of the very large atom count, presence of a transition metal center (Co), and the extreme conformational complexity produced by extensive side chains and ionizable groups.

Charge, Polarity, and LogP

Formal charge (reported): 0.
The cobalt center is formally in a higher oxidation state and coordinated within the corrin macrocycle while the axial cyanide ligand stabilizes the complex; despite the metal center, the intact complex presents as an overall neutral, highly polar molecule due to multiple ionizable and hydrogen-bonding functionalities.
Lipophilicity: class-level behavior is strongly hydrophilic; the molecule partitions preferentially to aqueous phases and requires polar solvents or complexing agents for transfer into nonpolar media.
No experimentally established value for this property is available in the current data context for logP or octanol–water partition coefficient.

Biochemical Classification

Cyanocobalamin is a cobalamin (corrinoid) vitamin, a member of the corrin macrocycle family of organometallic cofactors. It is a synthetic or isolated cyanide-bearing derivative of vitamin B12 used as a stable storage and dosing form; in biological systems it serves as a precursor to enzymatically active forms (methylcobalamin and 5'-deoxyadenosylcobalamin) that act as coenzymes for one‑carbon transfer and intramolecular rearrangement reactions.

Chemical Behavior

Stability and Degradation

Cyanocobalamin is comparatively chemically stable among cobalamin derivatives because the cyanide axial ligand forms a relatively robust bond to the Co(III) center, which reduces susceptibility to certain ligand-exchange reactions under mild conditions. However, it is chemically labile under several stressors typical for complex cofactors: - Photolysis can lead to ligand dissociation and reduction of the cobalt center, promoting conversion to other cobalamin forms or degradation products. - Strong reducing environments and enzymatic reductive activation facilitate conversion of cyanocobalamin to other cobalamins (via reduction and ligand exchange). - Extreme pH, prolonged heating, and strong oxidizing or nucleophilic conditions promote hydrolytic cleavage of peripheral amide or glycosidic linkages and decomposition of the nucleotide loop. Handling and formulation strategies generally emphasize protection from light, reducing agents, and extreme pH to preserve chemical integrity.

Hydrolysis and Transformations

Cyanocobalamin undergoes ligand-exchange reactions at the cobalt axial position and biochemically is converted into active cobalamin derivatives: - The cyanide ligand can be displaced under reducing/enzymatic conditions to yield hydroxocobalamin, methylcobalamin, or adenosylcobalamin depending on the reaction pathway and enzymatic context. - The phosphorylated ribose (nucleotide) moiety and several amide side chains are susceptible to hydrolysis under strong acidic or basic conditions, which can fragment the molecule and destroy cofactor activity. - Photochemical and reductive pathways can reduce Co(III) to Co(II) or Co(I), enabling Co–ligand bond cleavage and subsequent rearrangements; these transformations are central to the conversion between different biologically relevant cobalamin species. These transformation pathways underpin the use of cyanocobalamin as a pharmaceutically stable precursor that is metabolically converted to active forms in vivo.

Biological Role

Functional Role and Pathways

Cyanocobalamin itself acts primarily as a stable delivery form of vitamin B12; in biological systems it is enzymatically or chemically converted to the active cofactors: - Methylcobalamin: cofactor for methionine synthase (homocysteine methylation to methionine) and central to folate and one-carbon metabolism. - 5'-Deoxyadenosylcobalamin (adenosylcobalamin): cofactor for methylmalonyl-CoA mutase (isomerization of methylmalonyl-CoA to succinyl-CoA) in mitochondrial odd-chain fatty acid and amino acid catabolism. These cobalamin-dependent reactions are essential for nucleotide biosynthesis, methylation chemistry, and intermediary metabolism.

Physiological and Cellular Context

Within organisms, cobalamins are transported by specific binding proteins and cellular uptake systems; cyanocobalamin delivered exogenously is taken up, processed, and converted into physiologically active cofactor forms in cellular compartments: - Cytosolic conversion supplies methylcobalamin for methionine synthase activity. - Mitochondrial import and conversion yield adenosylcobalamin for mutase activity. Cellular homeostasis of cobalamins is tightly regulated; deficiency impairs DNA synthesis and metabolic flux through one‑carbon and odd‑chain carbon metabolism pathways.

Identifiers and Synonyms

Registry Numbers and Codes

CAS Registry Number: 68-19-9
InChIKey: FDJOLVPMNUYSCM-WZHZPDAFSA-L
InChI: InChI=1S/C62H90N13O14P.CN.Co/c1-29-20-39-40(21-30(29)2)75(28-70-39)57-52(84)53(41(27-76)87-57)89-90(85,86)88-31(3)26-69-49(83)18-19-59(8)37(22-46(66)80)56-62(11)61(10,25-48(68)82)36(14-17-45(65)79)51(74-62)33(5)55-60(9,24-47(67)81)34(12-15-43(63)77)38(71-55)23-42-58(6,7)35(13-16-44(64)78)50(72-42)32(4)54(59)73-56;1-2;/h20-21,23,28,31,34-37,41,52-53,56-57,76,84H,12-19,22,24-27H2,1-11H3,(H15,63,64,65,66,67,68,69,71,72,73,74,77,78,79,80,81,82,83,85,86);;/q;-1;+3/p-2/t31-,34-,35-,36-,37+,41-,52-,53-,56-,57+,59-,60+,61+,62+;;/m1../s1
SMILES: CC1=CC2=C(C=C1C)N(C=N2)[C@@H]3[C@@H]([C@@H]([C@H](O3)CO)OP(=O)([O-])O[C@H](C)CNC(=O)CC[C@@]\\4([C@H]([C@@H]5[C@]6([C@@]([C@@H](C(=N6)/C(=C\\7/[C@@]([C@@H](C(=N7)/C=C\\8/C([C@@H](C(=N8)/C(=C4\\[N-]5)/C)CCC(=O)N)(C)C)CCC(=O)N)(C)CC(=O)N)/C)CCC(=O)N)(C)CC(=O)N)C)O.[C-]#N.[Co+3]

(Each of the above identifiers is provided in the formats shown; registry and structural codes are used for unambiguous substance identification.)

Synonyms and Biological Names

Reported synonyms and names include: - Cyanocobalamin (Vitamin B12) - cyanocobalamin - vitamin B12 - SCHEMBL29674629

Safety and Handling Overview

Handling and Storage of Biochemical Materials

Chemical class hazards and handling: as a large, hydrophilic corrinoid, cyanocobalamin is not highly volatile but can be sensitive to photodegradation, heat, and reducing agents. Minimize light exposure during handling and storage; use opaque or amber containers where possible and limit exposure to strong reducing conditions or extreme pH that accelerate degradation.
Personal protective measures: standard laboratory PPE (gloves, eye protection, lab coat) is appropriate for routine solid handling and solution preparation; avoid inhalation of dust by employing local ventilation or dust control during weighing of powdered material.
Storage: store protected from light and in dry conditions; follow supplier recommendations for temperature control and packaging to maintain stability.
Waste and spill management: treat solids and solutions as laboratory chemical waste; contain and collect spilled material with inert absorbents, avoiding release to drains without appropriate neutralization or institutional controls. For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.