Question

please help. i have to provide stereochemical assignments. (R or S and E or Z) for the four below.

НО ОН HOVH ОН " ОН 5 6 11 NH2 Br

Answer 1

Auswer Stereochemical assignments (Rors) and (E or Zl nomenclature carried out by following the CIP rule : Accordingly to the Cahn- Ingold-Prelog (CIP) rule to give nomenclature of my chiral centre we have to follow priority of attached ligand or substituent attached to the chiral carbon atom. Priority of any chiral centre should be on the basis of atomic no on atomic mass. не eg 2 By— I- a OH 3 Direction of priority has shown. ie ① → ② ③ 4 Rule]: (1) if priority direction is clockwise and lowest priority atom is horizontal then it will be 's' configuration (2) If priority direction is anticlockwise and lowest priority - atom is horizontal then it will be ® configuration » If priority direction is clockwise and lowest priority atom is vertically then it will be 'R' configuration - ① If priority direction is anficlockwise and lowest priority - atom is vertically then it will be 'S' configuration

@ Rules for E and 2 nomenclaline This is done only ban akene type system 1. ФА Carlo B ,E @ A B7 E@ case -1 (2) case-2 CE) If same priority atoms or group are on the same side like case- ł then this will be zoalkene . 1 (11) If same priority atoms or group are on ou are on the - opposite side or direction like case-2 then this will be E-alkene. 1. the give molecules rule Thus following all above were assiguiend WwWS OH Ho HONE AR U1 4OH How 21 HOH

this two carbon centre is not chiral. as it is having same substituent enviroment. For that reason assignment is not needed, ][z)=(2) NH2 ROH Е Он This is not a cheral as it is having same substituent environment, so assignment is not needed.