RS System of nomenclature for isomers with 1+ stereorgenic center.A kind of 3-bromo-2-butanol H HCH3-C-C-CH3 OH Br(Two hydrogen atom on the same side)when determining the configuration @ C-2, I thought the priority of-OH would be 1, and -CHBrCH3 would be 2, but the textbook explainedthat 'the group with the lowest priority is on a HORIZONTAL bond' soC-2 is S configuration, instead of R.

丁醇的同分异构?

恩，但Horizontal Bond不解。

Horizontal Bond 平行键？