The enantiopure alcohol shown is converted to its tosylate with TsCl and pyridine, and the tosylate is then treated with $\mathrm{NaN}{}_3$ in DMF ($\mathrm{S}{}_{\mathrm{N}}2$). What is the configuration of the azide product?

The compound is (S)-butan-2-ol. Tosylation breaks the O-H bond, not the C-O bond, so the stereocentre keeps its arrangement. Azide then displaces tosylate with inversion. Writing the product with the opposite wedge and checking CIP (N > ethyl > methyl > H) gives R: (R)-2-azidobutane.