Propargyl bromide (also known as 3-bromopropyne) is a halopropyne compound with a bromine functional group. Propargy bromide can be used as an alkylating agent and an intermediate in the synthesis of organic compounds, agricultural chemicals and drugs, and is used to manufacture other chemicals. It reacts with magnesium in the presence of ether to obtain a Grignard reagent, allylmagnesium bromide, which further reacts with propargyl bromide to prepare bispropylene 1,2,4,5-hexatetraene. It is also used as a metal brightener, corrosion inhibitor and soil fumigant.

Chemical properties

Propargyl bromide appears as a colorless to pale yellow liquid with a pungent odor. The flash point is 65°F (18°C). It has a density greater than that of water, is insoluble in water, and is miscible with ethanol, ether, benzene, carbon tetrachloride, and chloroform. Its vapor is heavier than air. It is light-sensitive and incompatible with alkalis, strong oxidants, copper, peroxides, silver, silver oxide, mercury, and mercuric oxide. It may irritate the skin and eyes. It is highly flammable, and combustion can produce irritants and toxic gases, and it can decompose explosively with a slight impact.

Applications

Propargyl bromide can be used to synthesize poly(propargyl pyridinium bromide). This is a conjugated polyelectrolyte with polyacetylene as the backbone and pyridine as the side group, synthesized by the reaction of pyridine with propargyl bromide under mild conditions. The polymer itself has very weak fluorescence intensity, but the addition of some anions to the polymer solution in DMF or DMSO can enhance the fluorescence by up to 25 times. In addition, heating the polymer solution between 70~130°C for more than 0.5 h significantly enhances the fluorescence intensity. The interaction with anions or heating enhances the effective exciton confinement within the conjugated backbone, resulting in fluorescence enhancement. After fluorescence enhancement, poly(propargyl pyridinium bromide) has relatively strong fluorescence emission, which will make it have good prospects in fluorescence-based applications.

In addition, a solution of propargyl bromide (40 mL, 0.53 mol) and triphenylphosphine (13.9 g, 53 mmol) in 200 mL of toluene was heated to 70°C. After 15 hours, propargyl bromide was isomerized to give I-Bromopropadiene.

References:

[1] CHANGMING ZHOU; Daoyong C; Yong Gao. Investigation of Pyridine/Propargyl Bromide Reaction and Strong Fluorescence Enhancements of the Resultant Poly(propargyl pyridinium bromide)[J]. The Journal of Physical Chemistry B, 2012, 116 37: 11552-11559. DOI:10.1021/jp305298x.

[2] B. K?NIG; B. E. Triphenylphosphine-catalyzed Isomerisation of Propargyl Bromide to 1-Bromopropadiene[J]. Synthetic Communications, 1997, 27 1: 1685-1688. DOI:10.1080/00397919708004078.