Question

a) (i) Define both Ka and oka with specific reference to the reaction of substituted pyridines given below, or another reaction of your own choosing. Identify the acid, base, conjugate acid and conjugate base. Describe briefly the origin of the Hammett ox values. In your answer, give details about the reaction used to derive these values. The pka values for the reaction of pyridinium ions, as well as Hammett ox values(para) are provided in Table 2. Define a Hammett p (rho) parameter for this reaction and demonstrate how it is obtained by estimating p (rho) from the data provided. You may use a calculator and/or graph paper. Comment on the significance of the magnitude and sign of the p value obtained with reference to the acidity of pyridinium ions. Table 2. Hammett opara values corresponding to substituents X and pka values of corresponding pyridinium ions. +HO +H30 pyridinimion X H NH2 CHO CH al Br CN para 0 -0.62 -0.29 -0.17 0.22 0.23 0.67 pka 5.21 9.12 6.58 6.03 3.83 3.75 1.86

Answer 1

1. We
   H 6 +H₂O + H₂ A x of the The equillitrium constant process (ka) kw? * H₂ equillibrum constant. Water is, concentration en ene nf in large excommunication been taken pka 2 - log o ka H Here act as X H₂ot) aut as a contingate acid, act as conjugate Base conjugate acid aut ON act as The Modified base conjingate no Brown has applied. Hammett equation for the quantitative brediett of partial roate factors. od results for the relative of meta x para positions. Hammett equation is written good & has obtained reactivitieo The modified RO - s REDMI NOTE 5 PRO Substituent Constant MI DUAL CAMERA reaction constant logfa oo
   
   for the pashal rate factors, which is represented onvenient method expression of orientation aromatic quran & reactivity in Is througer the substitution the rate as f, It may be defined of Suresh tubin ar ageven posities in Substituted of ang benzene to that in benzene quantitative measure or election withdrand of the position value. election - positive elecrow releasing ing power of a substituent group & may have a negative o values, indicates with asawing that mature of the substituent resulting deactivation of aromatica sing, negative value indicates. electrons donationi by the substituents. in the whereas. f is sensitivities of the a measure of the Nasion, reaction series, chartrages the polarity of the Substituents. It haars usually negative Value & lies between We lise partial rode factor (pobof pf (combo) Tog plotag. apf16) =pha 2pf (6) otxe a pka O 0.62 -NHL elo undefined - 14 7 -22.6 0.29 9. 12 8.58 REDMI NOTE 5 PRO MI DUAL CAMERA -35.40
   
   0.67 Lager negative value then the on the rate of substinents. I malles values. Indientes tens Influences