Methods and apparatus to produce alkynes are described. The method includes combusting fuel and an oxidizer in a combustion zone to create a carrier gas stream, which is accelerated to supersonic speed in an expansion zone. A feedstock material is injected into a feedstock injection zone using two or more pluralities of injection nozzles. The injection nozzles are arranged annularly. The carrier gas stream is transitioned from supersonic speed to subsonic speed to create a shockwave in a reaction zone. The reaction zone is directly connected to the feedstock injection zone, and the shockwave is created adjacent to the feedstock injection zone. The carrier gas stream and the feedstock material are simultaneously mixed and reacted.