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Self Assessment |
Chapter 9 : Alkynes |
| Qu 1: | Using the following average bond energies, estimate the strength of the p bonds in an alkyne and an alkene | ||||||||
| CºC = 820 kJ/mol (196 kcal/mol), C=C = 611 kJ/mol (146 kcal/mol), C-C = 368 kJ/mol (88 kcal/mol) | |||||||||
| Qu 2: | Consider the following points about the reaction of 2-butyne with HBr | ||||||||
| (i) reaction
with 1 equivalent gives 2-bromo-2-butene (ii) reaction with excess gives 2,2-dibromobutane |
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| (a) What conclusions can you reach about the reactivity of 2-bromo-2-butene compared to 2-butyne ? | |||||||||
| (b) Consider the two possible carbocations that could be formed in the conversion of 2-bromo-2-butene to 2,2-dibromobutane. Suggest a reason for the observed regioselectivity. | |||||||||
| Qu 3: | What would be the product from the reaction of propene with the following reagent sequence: | ||||||||
| (i) Br2 (ii) NaNH2 , heat (iii) NaNH2 then MeI | |||||||||
| Qu 4: | Show the major products, with stereochemistry where applicable, for the reactions of : | ||||||||
| (a) 1-pentyne and (b) 2-pentyne with each of the following : | |||||||||
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