Organosodium chemistry
Encyclopedia
Organosodium chemistry is the chemistry
of organometallic compounds containing a carbon
to sodium
chemical bond
. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds in the same group 1 elements row of the periodic table. Yet several important compounds exist.
Organometal bonds in group 1 are characterised by high polarity
and high nucleophilicity on carbon (compare electronegativity
of carbon (2.55) to that of lithium
0.98, sodium
0.93 potassium
0.82 rubidium
0.82). The principal organosodium compound of importance is sodium cyclopentadienide
that is prepared from sodium metal and cyclopentadiene
:
The higher alkali metals are known to metalate even some unactivated hydrocarbons and are known to self-metalate
Some organosodium compounds degrade by beta-elimination:
The carbanionic
nature of organosodium compounds can be minimized by resonance stabilization. For instance in Ph3CM compounds is rather stable and is even used as a reagent
.
Sodium also react with polycyclic aromatic hydrocarbon
via one-electron reduction
. With solutions of naphthalene
, it forms the deeply coloured radical sodium naphthalenide
.
In the Wanklyn reaction (1858) sodium replaces magnesium in a Grignard type reaction with carbon dioxide
:
In the original work the alkylsodium compound was accessed from the dialkylmercury compound by transmetallation. For example diethylmercury in the Schorigin reaction or Shorygin Reaction: 2Hg + 2Na → 2C2H5Na
, a mixture of n-butyllithium
and potassium tert-butoxide
. This reagent reacts with propene to the compound allyl potassium (KCH2CHCH2). cis-2-Butene and trans-2-butene equilibrate when in contact with alkali metals. Whereas isomerization is fast with lithium and sodium, it is slow with the higher alkali metals. The higher alkali metals also favor the sterically congested conformation.
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
of organometallic compounds containing a carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
to sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
chemical bond
Chemical bond
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...
. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds in the same group 1 elements row of the periodic table. Yet several important compounds exist.
Organometal bonds in group 1 are characterised by high polarity
Chemical polarity
In chemistry, polarity refers to a separation of electric charge leading to a molecule or its chemical groups having an electric dipole or multipole moment. Polar molecules interact through dipole–dipole intermolecular forces and hydrogen bonds. Molecular polarity is dependent on the difference in...
and high nucleophilicity on carbon (compare electronegativity
Electronegativity
Electronegativity, symbol χ , is a chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus...
of carbon (2.55) to that of lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
0.98, sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
0.93 potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
0.82 rubidium
Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group. Its atomic mass is 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in group 1, such as very rapid...
0.82). The principal organosodium compound of importance is sodium cyclopentadienide
Sodium cyclopentadienide
Sodium cyclopentadienide is an organosodium compound with the formula C5H5Na. The compound is often abbreviated as NaCp or CpNa, where Cp− is the cyclopentadienide anion. Cp is also used as an abbreviation for the cyclopentadienyl ligand in coordination chemistry.-Preparation:Sodium...
that is prepared from sodium metal and cyclopentadiene
Cyclopentadiene
Cyclopentadiene is an organic compound with the formula C5H6. This colorless liquid has a strong and unpleasant odor. At room temperature, this cyclic diene dimerizes over the course of hours to give dicyclopentadiene via a Diels–Alder reaction...
:
- 2 Na + 2 C5H6 → 2 NaC5H5 + H2HydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
The higher alkali metals are known to metalate even some unactivated hydrocarbons and are known to self-metalate
- 2 NaC2H5 → C2H4Na2 + C2H6
Some organosodium compounds degrade by beta-elimination:
- NaC2H5 → NaH + C2H4
The carbanionic
Carbanion
A carbanion is an anion in which carbon has an unshared pair of electrons and bears a negative charge usually with three substituents for a total of eight valence electrons. The carbanion exists in a trigonal pyramidal geometry. Formally a carbanion is the conjugate base of a carbon acid.where B...
nature of organosodium compounds can be minimized by resonance stabilization. For instance in Ph3CM compounds is rather stable and is even used as a reagent
Reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...
.
Sodium also react with polycyclic aromatic hydrocarbon
Polycyclic aromatic hydrocarbon
Polycyclic aromatic hydrocarbons , also known as poly-aromatic hydrocarbons or polynuclear aromatic hydrocarbons, are potent atmospheric pollutants that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. Naphthalene is the simplest example of a PAH...
via one-electron reduction
One-electron reduction
A one-electron reduction in organic chemistry involves the transfer of an electron from a metal to an organic substrate. It serves to differentiate between true organic reductions and other reductions such as hydride transfer reactions that actually involve two-electron species.The first...
. With solutions of naphthalene
Naphthalene
Naphthalene is an organic compound with formula . It is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings...
, it forms the deeply coloured radical sodium naphthalenide
Sodium naphthalenide
Sodium naphthalenide, also known as sodium naphthalide, is a soluble one-electron reductant employed in organic, organometallic, and inorganic chemistry. It is prepared by stirring sodium metal with naphthalene in a polar solvent such as tetrahydrofuran or dimethoxyethane, resulting in the...
.
- C10H8 + Na → Na+[C10H8]-•
In the Wanklyn reaction (1858) sodium replaces magnesium in a Grignard type reaction with carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
:
- C2H5Na + CO2 → C2H5CO2Na
In the original work the alkylsodium compound was accessed from the dialkylmercury compound by transmetallation. For example diethylmercury in the Schorigin reaction or Shorygin Reaction: 2Hg + 2Na → 2C2H5Na
Industrial applications
Although organosodium chemistry has been described to be of "little industrial importance", it once was central to the production of tetraethyllead. A similar Wurtz coupling-like reaction is the basis of the current industrial route to triphenylphosphine:- 3 PhCl + PCl3 + 6 Na → PPh3 + 6 NaCl
Organic derivatives of the heavier alkali metals
The higher alkali metals, organopotassium, organorubidium and organocaesium, are even more reactive than organosodium compounds and of limited utility. A notable reagent is Schlosser's baseSchlosser's base
Schlosser's base describes various superbasic mixtures of an alkyllithium compound and a potassium alkoxide. Commonly, the mixture is composed of n-butyllithium and potassium tert-butoxide. The reagent is named after Manfred Schlosser, though he uses the term LICKOR superbase ....
, a mixture of n-butyllithium
N-Butyllithium
n-Butyllithium is an organolithium reagent. It is widely used as a polymerization initiator in the production of elastomers such as polybutadiene or styrene-butadiene-styrene...
and potassium tert-butoxide
Potassium tert-butoxide
Potassium tert-butoxide is the chemical compound with the formula 3COK. This colourless solid is a strong base useful in organic synthesis. It exists as a tetrameric cubane-like cluster...
. This reagent reacts with propene to the compound allyl potassium (KCH2CHCH2). cis-2-Butene and trans-2-butene equilibrate when in contact with alkali metals. Whereas isomerization is fast with lithium and sodium, it is slow with the higher alkali metals. The higher alkali metals also favor the sterically congested conformation.