百科词条甲醛(formaldehyde) 2O$ $结构式:$ tikz \usepackage chemfig \begin document \chemfig = 2,0.5 O - 4.5,0.5 H - 7.5,0.5 H \end document作者:admin2026-08-16$$结构式:$\usepackage{chemfig} \begin{document} \chemfig{ (=[2,0.5]O) (-[4.5,0.5]H) (-[7.5,0.5]H) } \end{document}