( ( This ( chemical reaction ) ) ( ( produces ( combustable gas ) ) . ) )
(ROOT (S (NP (DT This) (NN chemical) (NN reaction)) (VP (VBZ produces) (NP (JJ combustable) (NN gas))) (. .)))
This chemical reaction produces combustable gas.
(ROOT (S (NP (NNP Combustion) (NNS reactions)) (VP (VBP involve) (S (NP (NP (DT the) (NN reaction)) (PP (IN of) (NP (NP (DT a) (NN hydrocarbon)) (PP (IN with) (NP (NN oxygen) (NN gas)))))) (VP (TO to) (VP (VB produce) (NP (NN water) (CC and) (NN carbon) (NN dioxide)))))) (. .)))