Two related halogenated hydrocarbons are shown below as condensed structural formulas
CHEMISTRY · Multi-part · A Level · Chemistry · Introduction to organic chemistry · Introduction to organic chemistry
Problem
Two related halogenated hydrocarbons are shown below as condensed structural formulas.
• Compound X: ClCH₂–CH₂Cl (1,2-dichloroethane)
• Compound Y: ClCH=CHCl (1,2-dichloroethene)
Both compounds contain two carbon atoms bonded to each other and one chlorine substituent on each carbon atom.
(a) Describe the extent to which free rotation about the carbon–carbon bond is expected at room temperature for each compound. Base your answer on the type of bond present between the two carbon atoms.
(b) Using orbital overlap arguments, explain why the rotational behavior you described in part (a) differs between Compound X and Compound Y.
(c) Predict whether geometric (cis/trans or E/Z) isomerism is possible for each compound and justify your prediction in terms of the rotational freedom you discussed.