Glycerol reacts with excess HI to form propene via unstable intermediate 1,2,3-triiodopropane. Further addition of HI to propene give 2-iodopropene by markovnikoff addition. So, option b is correct.

Introduction: In this reaction, glycerol is reacted with excess HI at room temperature and then with more HI at 426K. The final product obtained can be determined by analyzing the reaction mechanism and the products formed at each step. Reaction mechanism: The reaction mechanism involves the following steps: 1. Glycerol is first protonated by HI to form an intermediate. 2. The intermediate undergoes a series of rearrangements leading to the formation of an alkyl iodide. 3. The alkyl iodide formed can further react with HI to form a new intermediate. 4. This intermediate can undergo a series of reactions leading to the formation of a new alkyl iodide. 5. The process continues until all the hydroxyl groups in glycerol have been replaced by iodine atoms. Final product: The final product obtained from the reaction of glycerol with excess HI at room temperature and then with more HI at 426K is propanei.e. option (c). Explanation: The reaction mechanism shows that the glycerol molecule undergoes a series of rearrangements and reactions leading to the formation of an alkyl iodide. The alkyl iodide formed can further react with HI, leading to the formation of a new intermediate. This process continues until all the hydroxyl groups in glycerol have been replaced by iodine atoms. In the final step, the alkyl iodide formed from glycerol rearranges to form propane. This is because the rearrangement leads to the formation of a more stable and more substituted alkyl iodide. The more substituted alkyl iodide can then undergo elimination to form the final product, which is propane. Conclusion: The reaction of glycerol with excess HI at room temperature and then with more HI at 426K leads to the formation of propane as the final product. The reaction mechanism involves a series of rearrangements and reactions leading to the replacement of all the hydroxyl groups in glycerol by iodine atoms.