IBDP Chemistry Question Analysis Topic: Chemistry - Short Questions
Exam Questions:
1) CO(g) and H2(g) react to give different products in the presence of different catalyst. Which ability of the catalyst is shown by these reactions?
2) Account for the following.
Aromatic carboxylic acids do not undergo Friedel-Crafts reaction.
3) Write the structure of the alkene formed by dehydrohalogenation of 1-bromo-1-methylcyclohexane with alcoholic KOH.
Answers:
For IBDP Chemistry, you should know:
1) These chemicals react differently with different catalysts to make different products. These reactions show the phenomenon of catalyst selectivity, which is the catalyst's ability to direct a reaction such that only one particular product is made.
For instance, ZnO and Cr2O3 catalysts are utilised to make methanol from CO (g) and H2 (g). In the Fischer Tropsch process, Co and ThO2 catalysts are used to synthesize hydrocarbons from CO (g) and H2 (g).
2) Such acids do not undergo the Friedel-Crafts reaction because the carboxyl (-COOH) group deactivates. Moreover, the Lewis acid catalyst AlCl3 bonds to the carboxyl group. Through inductive and resonance effects, the carboxyl group withdraws electron density from the benzene ring.
3) 1-methylcyclohex-1-ene is formed when 1-bromo-1-methylcyclohexane is dehydrohalogenated with an alcoholic KOH.
The major product would be identified by C if there is a possibility that more than one alkene forms.
According to 1-methylcyclohex-1-ene, more substituted alkene would be the major product during dehydrohalogenation.
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