Phenylacetylene

• Ethinylbenzen (IUPAC)
• Ethynylbenzene
• Phenylacetylene

Yellowish liquid

Liquid

0.93 g · cm -3 ( 20 ° C)

-44.8 ° C

142-144 ° C (1013 hPa)

2.7 hPa ( 25 ° C)

0.46 g · l-1 in water (25 ° C)

1.547 (at 20 ° C, 589 nm)

Risk

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Phenylacetylene is the simplest aromatic alkyne. It is a colorless, viscous liquid with a flash point of 27 ° C. In research, it is sometimes used as analogue of acetylene, as a liquid, it is easier to handle than gaseous acetylene.

Production

In the laboratory, phenylacetylene, by elimination of hydrogen bromide from 1,2- Dibromphenylethan (also incorrectly referred to as Styroldibromid ) are obtained with sodium amide in liquid ammonia:

It can also by elimination of hydrogen bromide from 1 - or 2- Bromphenylethen (as trivial names 1 - or 2 -bromostyrene ) are made with molten potassium hydroxide.

Properties

As acetylene reacts its ethynyl group (-C ≡ C -H) against strong bases ( for example NaNH2 ) as an acid and shows other typical alkynes reactions such as electrophilic addition reactions, hydrogenation, or polymerizations. The vapors of phenylacetylene are flammable. The flash point is 31 ° C.

Reactions

• Can phenylacetylene by hydrogen over Lindlar's catalyst reduced to styrene ( hydrogenated) are.
• It trimerized under metal catalysis, 1,2,4 - (97%) and 1,3,5- triphenylbenzene (3%):

• It adds catalyzed by sodium tetrachloroaurate water. The initially formed enol tautomerization spontaneously acetophenone:

However, this reaction does not have any practical importance as acetophenone is prepared by a simple Friedel -Crafts acylation of benzene with acetyl chloride and Lewis acids.