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| 1. |
Why 1chloro 4metylbenzene is major product than 1chloro 2methyl bezene? |
| Answer» AUSE of the great reactivity of the chlorine radical, abstractions of primary, SECONDARY, and tertiary hydrogen atoms are all exothermic. Therefore, the stability of the product radical has less influence on the activation energy of the reaction. Thus, according to the Hammond postulate, the transition state is more reactant-like. According to R. Brückner Advanced Organic Chemistry, the chlorination of isopentane has four monochlorination products: 22 % 2-chloro-2-methylbutane 33 % 2-chloro-3-methylbutane 30 % 1-chloro-2-methylbutane 15 % 1-chloro-3-methylbutane The statistical factor is responsible for this. If each hydrogen atom of isopentane could be substituted at the same rate, the ratio would be 1 hydrogen atom (8 %) → 2-chloro-2-methylbutane 2 hydrogen atoms (17 %) → 2-chloro-3-methylbutane 6 hydrogen atoms (50 %) → 1-chloro-2-methylbutane 3 hydrogen atoms (25 %) → 1-chloro-3-methylbutane In terms per hydrogen atom, the experimental yield is 22 % / 1 = 22 % → 2-chloro-2-methylbutane 33 % / 2 = 16.5 % → 2-chloro-3-methylbutane 30 % / 6 = 5 % → 1-chloro-2-methylbutane 15 % / 3 = 5 % → 1-chloro-3-methylbutane Thus, 2-chloro-2-methylbutane is indeed slightly preferred – | |