Question

Part A Which of the following compounds can have stereoisomers? a) 2-pentene b) 2-chlorobutane c) 1-butene d) 2-methyl-1-butene Part B Which of the following compounds has both cis and trans isomers possible? a) 2-methyl-3-hexyne b) 1,2-dichloro-1-butene c) 2,3-dichloropentane d) 1,1-dibromopropene Part C Which of the following compounds are chiral? a) 2-bromo-2-chlorobutane b) ethane c) 2-bromo-2-chloropropane d) chloromethane Part D Which of the following compounds contains a chiral carbon molecule? a) chloroethane b) 1,1-dichloroethane c) dibromochloromethane d) 2-butanol

Answer 1

Answer:

Part A: 2- Pentene and 2-chlorobutane have stereoisomers

Part B: Only 1,2-dichloro-1-butene has both cis and trans isomer

Part C: Only 2-bromo-2-chlorobutane is chiral

Part D: Only 2-butanol contains a chiral carbon

Explanation:

Stereoisomerism is a phenomenon where by compounds have the same molecular formular but different spatial arrangement

There are 2 types of Stereoisomerism

1. Geometrical isomerism. This is sometimes called Cis and trans isomerism. This usually occurs in Alkenes. For a molecule to have cis and trans isomer, each carbon holding the double bonds must have two different groups around it.
2. Optical isomerism: A compound will have an optical isomer if it contains at least a chiral carbon. A chiral carbon is a carbon that is bonded to four (4) different groups around it in a molecule.

Part A: 2-pentene  has cis and trans isomer

            2-chlorobutane exhibit optical isomerism also. (option a and b)

Part B:  Only (option a) 1,2-dichloro-1-butene has cis and trans isomer

Part C: Only (option a) 2-bromo-2-chlorobutane has a chiral carbon. The chiral carbon is the 2nd carbon holding the Cl, Br, CH3 and C2H5 groups

Part D: Only (option D) 2-butanol has a chiral carbon. The 2nd carbon is the chiral carbon holding the H, OH, CH3 and C2H5 groups