( ( ( Remember also ) ( that ( ( sigma bonds ) ( ( are ( lower ( in energy ) ) ) ( than ( pi bonds ) ) ) ) ) ) ( , ( ( ( the ( alkene side ) ) ( of ( the reaction ) ) ) ( ( ( has ( one ( fewer ( sigma bond ) ) ) ) ( in ( exchange ( for ( the ( pi bond ) ) ) ) ) ) . ) ) ) )
(ROOT (S (S (VP (VB Remember) (ADVP (RB also)) (SBAR (IN that) (S (NP (NN sigma) (NNS bonds)) (VP (VBP are) (ADJP (ADJP (JJR lower)) (PP (IN in) (NP (NN energy)))) (PP (IN than) (NP (NN pi) (NNS bonds)))))))) (, ,) (NP (NP (DT the) (JJ alkene) (NN side)) (PP (IN of) (NP (DT the) (NN reaction)))) (VP (VBZ has) (NP (CD one) (JJR fewer) (NN sigma) (NN bond)) (PP (IN in) (NP (NP (NN exchange)) (PP (IN for) (NP (DT the) (NN pi) (NN bond)))))) (. .)))
Remember also that sigma bonds are lower in energy than pi bonds, the alkene side of the reaction has one fewer sigma bond in exchange for the pi bond.
(ROOT (S (NP (DT A) (JJ double) (NN bond)) (VP (VBZ consists) (PP (IN of) (NP (NP (CD one) (NN sigma) (NN bond)) (CC and) (NP (CD one) (NN pi) (NN bond))))) (. .)))