Cobalt(II) naphthenate

Cobalt(II) naphthenate

Names
Other names Naphtolite
Identifiers
CAS Number	61789-51-3 Y
PubChem	14048876
RTECS number	QK8925000
Properties
Chemical formula	CoC22H14O4
Molar mass	401.02 g/mol
Appearance	brown amorphous or bluish-red solid
Density	0.96 g/cm3, solid
Melting point	140 °C (284 °F; 413 K)
Boiling point	> 150 °C (302 °F; 423 K)
Solubility in water	none
Hazards
Flash point	48.89 °C (120.00 °F; 322.04 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Cobalt(II) naphthenate is a mixture of cobalt(II) derivatives of naphthenic acids. Cobalt Naphthenate is a cobalt source that is soluble in organic solvents as an organometallic compound (also known as metalorganic, organo-inorganic and metallo-organic compounds). Cobalt naphthenate is the cobalt salt of naphthenic acids. Naphthenic acids are a complex group of carboxylic acids with the general formula C, HZ~+~O~, where n indicates the carbon number and Z specifies the hydrogen deficiency resulting from ring formation. Cobalt naphthenate is thus a member of the metal carboxylates group. All of the metal carboxylate salts are designed to add metals to chemical reactions. They therefore are expected to dissociate into free metal and free acid. The high purity acetylacetonate anion complexes by bonding each oxygen atom to the metallic cation to form a chelate ring.Because of this property, Cobalt Naphthenate is commonly used in various catalysts and catalytic reagents for organic synthesis. These coordination complexes are widely used as oil drying agents for the autoxidative crosslinking of drying oils. Metal naphthenates are not well defined in conventional chemical sense that they are mixtures. They are widely employed catalysts because they are soluble in the nonpolar substrates, such as the alkyd resins or linseed oil. The fact that naphthenates are mixtures helps to confer high solubility. A second virtue of these species is their low cost. A well-defined compound that exhibits many of the properties of cobalt naphthenate is the cobalt(II) complex of 2-ethylhexanoic acid. Often in technical literature, naphthenates are described as salts, but they are probably also non-ionic coordination complexes with structures similar to basic zinc acetate.Cobalt naphthenate is used primarily in unsaturated polyester resins, paint drier applications and rubber adhesion promotion in the tire industry. One characteristic of cobalt naphthenate and other metal carboxylates is that they readily dissociate from an ion pair into free metal and free acid. They are found as partially dissociated products in the ambient environment (i.e., neutral pH). Dissociation is a reversible process and the proportion of dissociated salt is dependent on the pH and pKa (the dissociation constant), which is the pH at which 50% dissociation occurs. In the low pH environment of the digestive tract 3 (e.g., pH 1.2) complete dissociation will occur for these metal carboxylates. The transport and’bioavailability of the metals and acids are determined by their solubility in environmental media and biological fluids which is determined by environmental parameters such as pH. Dissociation is a reversible reaction, splitting the parent compound into two or more chemical species which may be ionic, but are not necessarily so. The processcan be generally represented as:

[RCOO’]x:[M+]-[RCOO-]x + [M’] -[RCOOH], + [M’]

undissociated salt dissociated acid and metal neutral species + ionized metal High pH Low pH The pKa and pH are equal when the metal carboxylate salt is 50% dissociated. The parent compounds, the metal carboxylate salts, are associated ionized molecules. Because the free acid (naphthenic acid) and corresponding free metal (cobalt) have different characteristics (e.g., solubility, adsorption, and toxicity) than the undissociated salt (ion pair), the proportion of dissociation influences the behavior of the substance in the environment.^[1]

The catalytic properties of cobalt(II) naphthenates are similar to those of related compounds containing manganese and iron. Such species are sometimes classified as active driers." Active driers are catalysts that feature redox-active metal centers. Such centers promote redox reactions with hydroperoxide-containing intermediates.^[2]

Toxicity

Cobalt is believed to exhibit its toxicity through an oxidant-based and free radical-based processes. It produces oxygen radicals and may be oxidized to ionic cobalt, causing increased lipid peroxidation, DNA damage, and inducing certain enzymes that lead to cell apoptosis. Cobalt has also been shown to block inorganic calcium channels, possibly impairing neurotransmission. Cobalt can also chelate lipoic acids, impairing oxidation of pyruvate or fatty acids. In addition, cobalt may inhibit DNA repair by interacting with zinc finger DNA repair proteins, and has also been shown to inhibit heme synthesis and glucose metabolism. Cobalt may activate specific helper T-lymphocyte cells and interact directly with immunologic proteins, such as antibodies (IgA and IgE) or Fc receptors, resulting in immunosensitization. Radioactive cobalt damages DNA, RNA, and lipids through ionizing events.^[3]

Mechanism

Cobalt is absorbed though the lungs, gastrointestinal tract, and skin. Since it is a component of the vitamin B12 (cyanocobalamin), it is distributed to most tissues of the body. It is transported in the blood, often bound to albumin, with the highest levels being found in the liver and kidney. Cobalt is excreted mainly in the urine and feces.^[4]

References