( ( This reaction ) ( therefore ( ( ( involves ( ( the transfer ) ( of ( a ( chlorine atom ) ) ) ) ) ( from ( ( one molecule ) ( to ( ( another , ) ( as ( ( shown ( in ( the figure ) ) ) below ) ) ) ) ) ) ) . ) ) )
(ROOT (S (NP (DT This) (NN reaction)) (ADVP (RB therefore)) (VP (VBZ involves) (NP (NP (DT the) (NN transfer)) (PP (IN of) (NP (DT a) (NN chlorine) (NN atom)))) (PP (IN from) (NP (NP (CD one) (NN molecule)) (PP (TO to) (NP (NP (DT another)) (, ,) (SBAR (IN as) (S (VP (VBN shown) (PP (IN in) (NP (DT the) (NN figure))) (ADVP (RB below)))))))))) (. .)))
This reaction therefore involves the transfer of a chlorine atom from one molecule to another, as shown in the figure below.
(ROOT (S (ADVP (RB Replace)) (NP (NP (DT another)) (PP (IN in) (NP (DT a) (NN molecule)))) (VP (VBZ happens) (PP (TO to) (NP (NNS atoms))) (PP (IN during) (NP (DT a) (NN substitution) (NN reaction)))) (. .)))
Replace another in a molecule happens to atoms during a substitution reaction.