Alkenes

To determine the identities of compounds X, Y, and Z, we will analyze the reactions and properties presented:

Step 1: Identify Alkene X

The alkene X is C₄H₈. Possible structures are 1-butene, 2-butene (cis and trans), and isobutene (2-methylpropene). Since X reacts with HBr to form a haloalkane Y, we apply Markovnikov's rule for the addition of HBr, where the bromine adds to the more substituted carbon. For isobutene (2-methylpropene), HBr predominantly forms tert-butyl bromide.

Step 2: Identify Y

When HBr reacts with isobutene, it forms tert-butyl bromide (2-bromo-2-methylpropane), C₄H₉Br. This reaction is supported by Markovnikov's rule.

Step 3: Identify Z

Y reacts with benzene in the presence of anhydrous AlCl₃ to undergo a Friedel-Crafts alkylation, forming a tert-butyl group attached to the benzene ring, creating tert-butylbenzene. This molecule is resistant to oxidation with KMnO₄ + KOH due to the stability of the tert-butyl group. The tert-butyl group does not have hydrogens on the alpha carbon, so oxidation by KMnO₄ is ineffective.

Therefore, X is isobutene (2-methylpropene), Y is tert-butyl bromide (2-bromo-2-methylpropane), and Z is tert-butylbenzene.