Which of the following opertions performed on the figuration of (S)-bu

1.	Which of the following opertions performed on the figuration of (S)-butan-2-ol has no effect?
Answer» Exchaging ligands acorss the horizontal bond Exchanging ligands acorss the vertical bond Making both switches`(1)` and `(2)` Exchanging a vertical and horizotanl ligand Solution :No change as it is equivalent to a `180^(@)` rotation in the plane of the paper. NOTE that a `180^(@)` horizontal or vertical rotation outside of the plane of the paper is not allowed because in any flipping out of the plane of the paper (side-to-side or top-to-bottom) the ligands formely projecting behind the plane of the paper end up projecting towards the VIEWER and those of formely pointing to the viewer end up behind the plane of the paper. Similarly a `90^(@)` rotation in the plane of the paper is not allowed. Writing `I` as `II` PRESUMES that the `H` and `OH` project behind the plane, but a `90^(@)`(or any other) rotation in the plane does not chnage the projection of bonds towards or away from the viewer.

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