We'll see in Chapter 11 that alkyl halides react with hydrosulfide ion (HS $^{-}$ ) to give a product whose stereochemistry is inverted from that of the reactant. Draw the reaction of $(S)-2$ -bromobutane with $\mathrm{HS}^{-}$ ion to yield 2 -butanethiol, $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}(\mathrm{SH}) \mathrm{CH}_{3} .$ Is the stereochemistry of the product $R$ or $S ?$