\newbox\monomera\setbox\monomera=%
\structure{\nopositioncheck\esingle\atom{C}
\side{\nsingle\atom{C}\epin{H$_3$}}
\atom{H}\esingle\atom{CH$_2$}}%
\newbox\monomerb\setbox\monomerb=%
\structure{\nopositioncheck\esingle\atom{C}
\side{\ssingle\atom{C}\epin{H$_3$}}
\atom{H}\esingle\atom{CH$_2$}}%
\newbox\monomere\setbox\monomere=%
\structure{\nopositioncheck\esingle\atom{C}
\side{\nsingle\atom{C}\epin{H$_3$}}
\atom{H}\esingle\atom{CH$_2$}\esingle\phantatom{}}%
\vbox{
\centerline{\copy\monomera\copy\monomera\copy\monomera%
\copy\monomera\copy\monomera\copy\monomere}
\medskip
\centerline{\copy\monomerb\copy\monomera\copy\monomerb%
\box\monomera\box\monomerb\box\monomere}
\medskip 
\centerline{\bf Figure~11. \rm Isotactic and syndiotactic 
polypropylene.}
}