Which of the following compounds can show optical isomerism? (a) dichloromethane (b) 1,2 -dichloroethane (c) bromochlorofluoromethane (d) 1 -bromoethanol

Since optical isomerism occurs in molecules with chiral centers, we need to identify the chiral centers in each of the given compounds. A chiral center is a carbon atom with four different groups attached to it. (a) dichloromethane (b) 1,2-dichloroethane (c) bromochlorofluoromethane (d) 1-bromoethanol

Let's look at the structures of these compounds and determine if they have carbon atoms with four different groups attached to them. (a) Dichloromethane: CH2Cl2 The carbon atom is bonded to two hydrogen atoms and two chlorine atoms, so it does not have four different groups attached. (b) 1,2-dichloroethane: ClCH2CH2Cl Neither of the two carbon atoms have four different groups attached; both carbon atoms have two hydrogen atoms and one chlorine atom attached to them. (c) Bromochlorofluoromethane: CHBrClF The carbon atom in this compound is bonded to a hydrogen, a bromine, a chlorine, and a fluorine atom. It has four different groups attached. (d) 1-bromoethanol: CH2BrCH2OH The carbon atom with the bromine group attached has two hydrogen and one oxygen atom bonded to it, so it does not have four different groups attached. The other carbon atom with the hydroxyl group attached has two hydrogen atoms, one bromine atom, and one oxygen atom bonded to it, so it does not have four different groups attached either.

Based on our examination of the compounds for chiral centers, we can conclude that only bromochlorofluoromethane (c) has a chiral center and can exhibit optical isomerism. The other compounds do not have chiral centers and thus cannot show optical isomerism.