When phenol is sulphonated by fuming sulfuric acid at a lower temperature, the ortho product is the major whereas at higher temperature the para product is formed as the major.

Why does this happen, because looking at the reaction mechanism, it appears to me that para should always be the major.

Is it the kinetic control vs thermodynamic control effect?? If yes, then why is para thermodynamically more stable and ortho kinetically faster??

  • $\begingroup$ Check this $\endgroup$ – Zenix Nov 26 '19 at 14:59
  • $\begingroup$ It's because at lower temperature H-bonding exert extra stability to ortho product while at higher temperature H bond get break so stability of o-product become less than para product $\endgroup$ – Abhishek kumar sahu Apr 2 at 17:30

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