Lithium carbide
Encyclopedia
Lithium carbide, Li2C2, often known as dilithium acetylide, is a chemical compound of lithium
and carbon
, an acetylide. It is an intermediate compound produced during radiocarbon dating
procedures. Li2C2 is one of an extensive range of lithium-carbon compounds which include the lithium-rich Li4C, Li6C2, Li8C3, Li6C3, Li4C3, Li4C5, and the graphite intercalation compound
s LiC6, LiC12, and LiC18.
Li2C2 is the thermodynamically-stable lithium-rich compound and is the only one of them that can be obtained directly from the elements. It was first produced by Moissan
, in 1896 who reacted coal with lithium carbonate
. The other lithium-rich compounds are produced by reacting lithium vapor with chlorinated hydrocarbons, e.g. CCl4
.
Lithium carbide is sometimes confused with the drug lithium carbonate
, Li2CO3, because of the similarity of its name.
are reacted at high temperature. Li2C2 can also be prepared by reacting CO2 with molten lithium. It is reactive and hydrolyses very readily to form acetylene
gas, C2H2, and LiOH.
that is then reacted with lithium, and others where the carbon containing sample is reacted directly with lithium metal. The outcome is the same: Li2C2 is produced, which can then be used to create species easy to mass, like acetylene and benzene. Note that lithium nitride
may be formed and this produces ammonia
when hydrolyzed, which contaminates the acetylene gas.
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...
and 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...
, an acetylide. It is an intermediate compound produced during radiocarbon dating
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
procedures. Li2C2 is one of an extensive range of lithium-carbon compounds which include the lithium-rich Li4C, Li6C2, Li8C3, Li6C3, Li4C3, Li4C5, and the graphite intercalation compound
Graphite intercalation compound
Graphite intercalation compounds are complex materials having formula XCy where element or molecule X is inserted between the graphite layers. In this type of compound, the graphite layers remain largely intact and the guest molecules or atoms are located in between...
s LiC6, LiC12, and LiC18.
Li2C2 is the thermodynamically-stable lithium-rich compound and is the only one of them that can be obtained directly from the elements. It was first produced by Moissan
Henri Moissan
Ferdinand Frederick Henri Moissan was a French chemist who won the 1906 Nobel Prize in Chemistry for his work in isolating fluorine from its compounds.-Biography:...
, in 1896 who reacted coal with lithium carbonate
Lithium carbonate
Lithium carbonate is a chemical compound of lithium, carbon, and oxygen with the formula Li2CO3. This colorless salt is widely used in the processing of metal oxides and has received attention for its use in psychiatry. It is found in nature as the rare mineral zabuyelite.-Properties:Like almost...
. The other lithium-rich compounds are produced by reacting lithium vapor with chlorinated hydrocarbons, e.g. CCl4
Carbon tetrachloride
Carbon tetrachloride, also known by many other names is the organic compound with the formula CCl4. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent...
.
Lithium carbide is sometimes confused with the drug lithium carbonate
Lithium carbonate
Lithium carbonate is a chemical compound of lithium, carbon, and oxygen with the formula Li2CO3. This colorless salt is widely used in the processing of metal oxides and has received attention for its use in psychiatry. It is found in nature as the rare mineral zabuyelite.-Properties:Like almost...
, Li2CO3, because of the similarity of its name.
Structure
Li2C2 is a salt formulated 2Li+C22−. It has a similar structure to that of Rb2O2 and Cs2O2. At high temperatures Li2C2 transforms reversibly to a cubic anti-fluorite structure.Preparation and chemistry
To prepare pure samples in the laboratory molten lithium + graphiteGraphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
are reacted at high temperature. Li2C2 can also be prepared by reacting CO2 with molten lithium. It is reactive and hydrolyses very readily to form acetylene
Acetylene
Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...
gas, C2H2, and LiOH.
Use in radiocarbon dating
There are a number of procedures employed, some that burn the sample producing CO2Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
that is then reacted with lithium, and others where the carbon containing sample is reacted directly with lithium metal. The outcome is the same: Li2C2 is produced, which can then be used to create species easy to mass, like acetylene and benzene. Note that lithium nitride
Lithium nitride
Lithium nitride is a compound of lithium and nitrogen with the formula Li3N. It is the only stable alkali metal nitride...
may be formed and this produces ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
when hydrolyzed, which contaminates the acetylene gas.