Chapter 11, Problem 57P

When the 3-bromo-2-butanol with the stereochemical structure A is treated with concentrated HBr, it yields meso-2, 3-dibromobutane; a similar reaction of the 3-bromo-2-butanol B yields $(\pm )$ -2, 3-dibromobutane. This classic experiment performed in 1939 by S. Winstein and H. J. Lucas was the starting point for a series of investigation of what are called neighboring group effects. Propose mechanisms that will account for the stereochemistry of reactions.