Latexむずい

うまくいかねえ…

 \ce{\hbox to5zw{\ethyleneh{1==C;2==C}{1==R1;2==R2;3==R3;4==R4}} + HX -> \tetrahedral{0==C;1==R1;2==R2;3==H;4==\tetrahedral{0==C;1==R3;2==(yl);3==R4;4==HX}} }\\\hline