( ( ( Chemical reactions ) ( that ( produce ( ( energy or ) that ) ) ) ) ( ( require ( energy 4 ) ) . ) )
(ROOT (S (NP (NP (NNP Chemical) (NNS reactions)) (SBAR (WHNP (WDT that)) (S (VP (VBP produce) (NP (NP (NN energy)) (CC or) (NP (DT that))))))) (VP (VBP require) (NP (NN energy) (CD 4))) (. .)))
Chemical reactions that produce energy or that require energy 4.
(ROOT (S (NP (NP (DT The) (NN amount)) (PP (IN of) (NP (NP (NN energy)) (VP (VBN required) (S (VP (TO to) (VP (VB begin) (NP (DT a) (JJ chemical) (NN reaction))))))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (DT the) (NN activation) (NN energy))))) (. .)))