▁and ▁Si 6 H 1 2 . ▁They ▁are ▁very ▁re active , ▁py roph or ic ▁colour less ▁g ases ▁or ▁vol atile ▁liqu ids . ▁Their ▁vol at ility ▁is ▁intermediate ▁between ▁the ▁al kan es ▁and ▁the ▁g erman es . ▁Un s atur ated ▁sil anes , ▁the ▁sil enes ▁and ▁sil yn es , ▁have ▁been ▁character ized ▁spect ro scop ically . ▁ ▁The ▁first ▁members ▁of ▁each ▁respectively ▁are ▁dis il ene ▁and ▁dis ily ne , ▁the ▁sil icon ▁analog ues ▁of ▁eth yl ene ▁and ▁ac et yl ene ). ▁The ▁first ▁five ▁g erman es ▁Gen H 2 n + 2 ▁are ▁known ▁and ▁are ▁fairly ▁similar ▁to ▁the ▁sil anes . ▁St ann ane , ▁a ▁strong ▁reducing ▁agent ▁slowly ▁decom poses ▁at ▁room ▁temperature ▁to ▁tin ▁and ▁hydro gen ▁gas , ▁and ▁is ▁decom posed ▁by ▁concentr ated ▁a que ous ▁ac ids ▁or ▁alk alis ; ▁dist ann ane , ▁Sn 2 H 6 ▁is ▁still ▁more ▁un stable , ▁and ▁longer ▁st ann anes ▁are ▁unknown . ▁Pl umb ane ▁is ▁very ▁poor ly ▁character ised ▁and ▁is ▁only ▁known ▁in ▁trace ▁amounts : ▁even ▁at ▁low ▁temper atures , ▁synth esis ▁methods ▁that ▁yield ▁the ▁other ▁M H 4 ▁comp ounds ▁fail ▁to ▁give ▁P b H 4 . ▁No ▁other ▁pl um ban es ▁are ▁known . ▁ ▁Comp ounds ▁containing ▁hydro gen ▁and ▁multiple ▁group ▁ 1 4 ▁elements ▁are ▁known , ▁one ▁of ▁the ▁most