You need to do several things in the next 3 MarvinJS editors to depict the 3 step process (the how) for the conversion of a ketone to a hemiacetal. Note - I will be using HB as the acid (proton "dropper offer") and B:- as the conjugate base (proton "picker upper") to make the drawing quick and easy. B does not stand for boron in this context, it represents the conjugate base. Drawing alerts: i) Select the 2-electron flow arrow from the tool bar.
ii) When you click on the atom with the lone pair that will be converted to a bond, it will become large. Click on the lone pair closest to the atom with which you are making the bond AND while keeping the cursor button held down drag it toward the atom where you are going to make the bond until a green circle appears around that atom. A dotted line should then form between the 2 atoms making the bond (click here). ALSO when there is a choice, pick the closest atom.
iii) When converting a sigma bond to a lone pair, hover over the bond so that it glows green. Click on it and while holding down the click drag it toward the atom on which it will end up as a lone pair (that atom should also glow green.)
iv) If you use the 2D (or 3D) tool to check for weirdness, you should click the undo button to put the atoms back. (click here.)
v) There is a "start over" button if you want to start fresh (click here.) Notes: