Can somebody tell me how why they changed/choose the groups for vertical and horizontal lines. As far as I know the vertical lines represent group going away from us and horizontal depicts coming towards us but I can't figure out how to choose which groups lie vertically and which groups horizontally... I am hopelessly stuck in Fischer projections.
EDIT: What I am having difficulty is how to choose where o arrange the groups in the horizontal line.
Why is the H bond on the C1 is arranged to the right while the OH is arranged to the left while the opposite is in C2 in the fischer projections It would make more sense for OH to be on the right as it is coming out of the plane and would appear at right when seen from above. Why does dash line is at right while wedge line to the left. How to interpret?