A comprehensive kinetic and mechanistic study of different phenolsformaldehyde reactions

Department of Chemistry, SGTB Khalsa College, University of Delhi, Delhi-110 007, India
E-mail : psj.sgtb57@gmail.com
Manuscript received 25 November 2009, revised 26 October 2010, accepted 28 October 2010

Kinetic study of the reaction of 2-tertlary butyl 6-methyl phenol with formaldehyde has been made at 338, 343, 348 and 353 K and at pH values of 10.0, 10.4, 10.8 and 11.2 using sodium hydroxide as catalyst. Reaction follow~ an overall second order rate law with the formation of 4-methylol 2-tertiary butyl 6-methyl phenol. Activation energy, I!.E and entropy of activation, ΔS^#_obs values were calculated using the linear plots or log k versus 1/T. Effect of the polarity of solvents i.e. methanol, ethanol, isopropanol and 1,4-dioxan show that rate of the reaction is highest in 1,4- dioxan. Catalysis by Lewis bases, MEA, DEA, TEA and TEAH exihibit that MEA acts as weak Lewis base and TEAH as a strong base. A comparative study of the reactivities of different phenols viz. 2,4-xylenol, phenol, m-cresol and saligenin- formaldehyde reactions reveal that rate is lowest in the case of 2-tertiary butyl 6-methyl phenol-formaldehyde reaction and highest in saligenin-formaldehyde reaction. The calculated and experimental values of second order rate constant at different temperatures and at pH value of 11.0 agree well within the experimental error.