Which of the following molecules does NOT represent (2S,3R)-2-bromo-3-chlorobutane?
1) (2S,3R)-2-bromo-3-chlorobutane
2) (2R,3S)-2-bromo-3-chlorobutane
3) (2S,3S)-2-bromo-3-chlorobutane
4) (2R,3R)-2-bromo-3-chlorobutane