( ( ( The reason ) ( ( these substances ) ( are bases ) ) ) ( ( is ( that ( they ( ( dissolve ( in water ) ) ( to ( release ( hydroxide ions ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN reason)) (SBAR (S (NP (DT these) (NNS substances)) (VP (VBP are) (NP (NNS bases)))))) (VP (VBZ is) (SBAR (IN that) (S (NP (PRP they)) (VP (VB dissolve) (PP (IN in) (NP (NN water))) (S (VP (TO to) (VP (VB release) (NP (JJ hydroxide) (NNS ions))))))))) (. .)))
The reason these substances are bases is that they dissolve in water to release hydroxide ions.
(ROOT (S (NP (NNS Bases)) (VP (VBP are) (NP (NP (DT the) (JJ ionic) (NNS compounds)) (SBAR (WHNP (WDT that)) (S (VP (VBP produce) (NP (JJ negative) (NN hydroxide) (NNS ions)) (SBAR (WHADVP (WRB when)) (S (VP (VBN dissolved) (PP (IN in) (NP (NN water))))))))))) (. .)))