Diphenylacetylene
Diphenylacetylene is a chemical compound with the molecular formula C6H5C≡CC6H5. It consists of two phenyl groups attached to a C2 unit and is a colorless solid[1]. This compound is used as a building block in organic synthesis and as a ligand in organometallic chemistry.
Preparation and Structure
Diphenylacetylene can be prepared through various methods. One method involves the condensation of benzil with hydrazine to form the bis(hydrazone), which is then oxidized with mercury(II) oxide. Another method involves the bromination of stilbene, followed by dehydrohalogenation of the resulting dibromodiphenylethane. The Castro-Stephens coupling and the related Sonogashira coupling are also used to prepare diphenylacetylene[1].
The molecule is planar, with a central C≡C distance of 119.8 picometers[1].
Derivatives
Diphenylacetylene reacts with tetraphenylcyclopentadienone to form hexaphenylbenzene in a Diels–Alder reaction. It also undergoes alkyne trimerisation catalyzed by dicobalt octacarbonyl to form hexaphenylbenzene. Reaction with benzal chloride in the presence of potassium t-butoxide yields 3-tert-butoxy-1,2,3-triphenylcyclopropene, which can be converted to 1,2,3-triphenylcyclopropenium bromide after the elimination of tert-butoxide[1].
Synthesis
The synthesis of diphenylacetylene involves a two-step process. The first step is the bromination of trans-stilbene to form meso-stilbene dibromide. This product is then subjected to dehydrohalogenation conditions to obtain diphenylacetylene[2][3].
Physical Properties
Diphenylacetylene is a solid with a melting point of 59-61°C. It has a density of 0.99 g/mL at 25°C[5].
Safety Notes
The synthesis of diphenylacetylene involves the use of corrosive and lachrymatory substances. It is essential to handle these reagents with care, wearing gloves and working in a fume hood[2][3].
Citations:
[1] https://en.wikipedia.org/wiki/Diphenylacetylene
[2] https://people.wou.edu/~courtna/ch335/Synthesis%20of%20Diphenylacetylene.pdf
[3] https://community.wvu.edu/~josbour1/Labs/F2016/Exp%2010%20-%20Diphenylacetylene.pdf
[4] http://www.orgsyn.org/demo.aspx?prep=CV3P0350
[5] https://www.sigmaaldrich.com/US/en/product/aldrich/d204803