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15. Give the mechanism of the following reactions. Show all intermediates. (5 Marks) HBr 16. Determine whether the following statements are true or false. Correct the false answer. (10 Marks) a) There are 8 stereoisomers of 3,5-dichloro-2-iodo- 6-bromoheptane. ( ) b) Cis-1,3-dimethylcyclobutane has no stereoisomers. c) A mixture of 75:25 of (R)-2-chlorobutane and (S)-2-chlorobutane is an optically active. ( ) d) Cis isomer of 1.4-diethylcyclohexane has higher energy than the trans isomer. ( )