( Alkenes ( ( ( react ( with ( ( water and ) halogens ) ) ) ( to ( ( form halohydrins ) ( by ( an ( addition reaction ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Alkenes)) (VP (VBP react) (PP (IN with) (NP (NN water) (CC and) (NNS halogens))) (S (VP (TO to) (VP (VB form) (NP (NNS halohydrins)) (PP (IN by) (NP (DT an) (NN addition) (NN reaction))))))) (. .)))
Alkenes react with water and halogens to form halohydrins by an addition reaction.
(ROOT (S (NP (NNS Alkenes)) (VP (VBP are) (VP (VBN formed) (PP (IN from) (NP (NP (DT an) (NN alcohol)) (SBAR (WHNP (WDT that)) (S (VP (VBZ loses) (NP (NN water))))))))) (. .)))