If I2 reacted with hexane, how would we know, which carbons the Is go on? Would only one of the iodine go to the hexane and the other form HI, or would they both join and H2 is a by-product?

Determining the product of a reaction between I2 and hexane requires understanding the mechanism and the possibility of multiple pathways. In this case, I2 is not likely to react directly with hexane. However, if hexane is treated with iodine, some reaction might occur, although not the substitution of iodine onto hexane's carbon atoms.

If we want to identify the potential reactions between I2 and hexane, we need to consider the nature of the reagents and typical reaction pathways. I2 is a nonpolar molecule, while hexane is a hydrocarbon composed of carbon and hydrogen atoms.

In general, iodine (I2) is primarily reactive towards compounds with unsaturated carbon-carbon bonds, such as alkenes or alkynes. The reaction typically involves the formation of a halonium ion intermediate, where the iodine is temporarily attached to the carbon-carbon double or triple bond.

However, hexane does not contain any unsaturated carbon-carbon bonds needed for a direct reaction with I2. Thus, I2 is unlikely to react directly with hexane under normal conditions.

If hexane is treated with iodine, it would be more likely that the reaction proceeds via a radical substitution mechanism. This would involve the homolytic cleavage of the I2 molecule to form iodine radicals (I•). These iodine radicals can then react with the hexane molecule to form alkyl iodides (e.g., R-I) and hydrogen iodide (HI) as a by-product.

Therefore, if hexane was to react with iodine, it is more probable that alkyl iodides would be formed, rather than iodine directly attaching to the carbon atoms of hexane.