Given the wedge-and-dash structure of $2_{}$-bromobutanol with the following configuration: the hydroxyl group ($\mathrm{OH}$) is on a wedge at carbon 2, the bromine ($\mathrm{Br}$) is on a dash at carbon 2, and the methyl group ($\mathrm{CH}{3}_{}$) and hydrogen are in the plane, which Fischer projection correctly represents this molecule?

• A. Vertical: $H$ (top), $\mathrm{CH}{3}_{}$ (bottom); Horizontal: $\mathrm{OH}$ (left), $\mathrm{Br}$ (right)
• B. Vertical: $\mathrm{Br}$ (top), $H$ (bottom); Horizontal: $\mathrm{OH}$ (left), $\mathrm{CH}{3}_{}$ (right)
• C. Vertical: $\mathrm{OH}$ (top), $\mathrm{Br}$ (bottom); Horizontal: $\mathrm{CH}{3}_{}$ (left), $H$ (right)
• D. Vertical: $\mathrm{CH}{3}_{}$ (top), $\mathrm{OH}$ (bottom); Horizontal: $\mathrm{Br}$ (left), $H$ (right)

Answer: (B)

Verified step by step guidance

1. Identify the stereocenter at carbon 2 of 2-bromobutanol and note the groups attached: hydroxyl (OH), bromine (Br), methyl (CH\_3), and hydrogen (H).
2. Understand the wedge-and-dash notation: a wedge indicates a bond coming out of the plane towards the viewer, and a dash indicates a bond going behind the plane away from the viewer. Here, OH is on a wedge (towards you), Br is on a dash (away from you), and CH\_3 and H are in the plane.
3. Recall that in Fischer projections, vertical lines represent bonds going away from the viewer (behind the plane), and horizontal lines represent bonds coming out of the plane (towards the viewer).
4. Assign the groups accordingly in the Fischer projection: groups on wedges in the 3D structure should be placed on horizontal lines in the Fischer projection, and groups on dashes should be placed on vertical lines.
5. Use this information to correctly position OH, Br, CH\_3, and H in the Fischer projection, ensuring that the stereochemistry (R or S configuration) is preserved by comparing the 3D arrangement with the 2D Fischer layout.