( ( The reaction ) ( ( produces ( ( essentially ( quantitative yield ) ) ( of ( pure product ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN reaction)) (VP (VBZ produces) (NP (NP (RB essentially) (JJ quantitative) (NN yield)) (PP (IN of) (NP (JJ pure) (NN product))))) (. .)))
The reaction produces essentially quantitative yield of pure product.
(ROOT (S (NP (NP (DT The) (NN amount)) (PP (IN of) (NP (NP (NN product)) (SBAR (WHNP (WDT that)) (S (VP (MD may) (VP (VB be) (VP (VBN produced) (PP (IN by) (NP (DT a) (NN reaction))) (PP (IN under) (NP (VBN specified) (NNS conditions))))))))))) (VP (VBZ is) (VP (VBN called) (NP (JJ theoretical) (NN yield)))) (. .)))
The amount of product that may be produced by a reaction under specified conditions is called theoretical yield.