▁has ▁become ▁an ▁important ▁tool ▁in ▁the ▁ ▁el uc id ation ▁the ▁mechanism ▁of ▁chemical ▁re actions . ▁De uter ium ▁contains ▁one ▁pro ton , ▁one ▁electron , ▁and ▁a ▁neut ron , ▁effectively ▁dou bling ▁the ▁mass ▁of ▁the ▁de uter ium ▁is ot ope ▁without ▁changing ▁its ▁properties ▁significantly . ▁However , ▁the ▁C - D ▁bond ▁is ▁a ▁bit ▁shorter , ▁and ▁it ▁has ▁reduced ▁electronic ▁polar iz ability ▁and ▁less ▁hyper con j ug ative ▁stabil ization ▁of ▁adjacent ▁b onds ▁( including ▁the ▁developing ▁anti - b ond ing ▁orb ital ▁of ▁a ▁newly - form ing ▁bond ). ▁It ▁potentially ▁can ▁result ▁in ▁we aker ▁van ▁der ▁Wa als ▁stabil ization , ▁and ▁it ▁can ▁produce ▁other ▁changes ▁in ▁properties ▁that ▁are ▁difficult ▁to ▁predict , ▁including ▁changes ▁in ▁the ▁intr am ole cular ▁volume ▁and ▁the ▁transition ▁state ▁volume . ▁Sub st itut ing ▁de uter ium ▁for ▁hydro gen ▁yields ▁de uter ated ▁comp ounds ▁that ▁are ▁similar ▁in ▁size ▁and ▁shape ▁to ▁hydro gen - based ▁comp ounds . ▁ ▁History ▁The ▁first ▁pat ent ▁in ▁the ▁US ▁granted ▁for ▁de uter ated ▁mole cules ▁was ▁in ▁the ▁ 1 9 7 0 s . ▁Since ▁then ▁pat ents ▁on ▁de uter ated ▁dru gs ▁have ▁become ▁more ▁pro l ific . ▁ ▁The ▁applications ▁of ▁the ▁de uter ium ▁is ot ope ▁effect ▁has ▁increased ▁over ▁time , ▁and ▁it ▁is ▁now ▁applied ▁extens ively ▁in ▁mechan istic ▁studies ▁of ▁the