\schemestart[][west]
\chemfig{-(-[2])(-[-2])-@{nu}\charge{90=\|,-90=\|}{O}H} \arrow{0}[,0]\+ \chemfig{@{el}\charge{180=\",45:3pt=$\scriptstyle\oplus$}{H}} 
\arrow{<=>}
\chemfig{-(-[2])(-[-2])-\charge{90=\|}{O}\charge{45:3pt=$\scriptstyle\oplus$}{H_2}}
\schemestop
\chemmove{
	\draw[shorten <=3pt,shorten >=4pt]
		(nu)..controls +(90:10mm) and +(160:10mm)..(el);
	}
	
\schemestart[][west]
\chemfig{-(-[2])(-[-2])-[@{ls}]@{el}\charge{90=\|}{O} @{h2}\charge{45:3pt=$\scriptstyle\oplus$}{H_2}}
\arrow{<=>}
\chemfig{-\charge{0:3mm=\"$\scriptstyle\oplus$}{}(-[::40])-[::-40]} \arrow{0}[,0]\+ \chemfig{H_2\charge{45=\|,-45=\|}{O}}
\schemestop
\chemmove{
	\draw[shorten <=1pt]
		(ls)..controls +(-90:5mm) and +(-120:5mm)..(el);
	}
	
\schemestart[][west]
\chemfig{-@{el}\charge{0:3mm=\"$\scriptstyle\oplus$}{}(-[@{ls}::40]-[@{lh}::60]H)-[::-40]} \arrow{0}[,0]\+ \chemfig{H_2\charge{45=\|,-45=\|}{O}}
\arrow{<=>}\chemfig{-[:-40](-[:-140])=} \arrow{0}[,0]\+ \chemfig{@{el}\charge{180=\",45:3pt=$\scriptstyle\oplus$}{H}} \arrow{0}[,0]\+ \chemfig{H_2\charge{45=\|,-45=\|}{O}}
\schemestop
\chemmove{
	\draw
		(lh)..controls +(-170:3mm) and +(130:3mm)..(ls);
	}