Hydrogen cyanide can add to a ketone to form a cyanohydrin (B) through the overall reaction:...

 

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Hydrogen cyanide can add to a ketone to form a cyanohydrin (B) through the overall reaction: HO + NaCN + H+ CN +Na+ R R' R R' (B) (A) The mechanism occurs in a (dilute) liquid solution as: 1) Dissociation of the NaCN, which can be considered equilibrated: NaCN Na* + CN 2) Nucleophilic addition of CN to the ketone: A+ CN ACN (anion) (equilibrium constant K:) (forward rate constant k, reverse rate constant k) 3) Protonation: ACN (anion) + H+ B (irreversible, forward rate constant k) The reaction is run in an isothermal continous reactor at 298 K. The values of equilibrium and rate constants at this temperature are given: K = 100 mol/L k = 110 L/mol-min k. = 10 min k = 1000 L/mol-min The volumetric flow rate through the reactor is 10 L/min, and the feed is equimolar in ketone (species A) and NaCN at 0.1 M/L. The inlet pH is 0.5. A 600 L reactor is to be used. Determine whether a 600 L CSTR or 600 L PFR will give a greater fractional conversion, and for whichever will get a higher conversion, determine the outlet concentrations of A, B, and the outlet pH. Hydrogen cyanide can add to a ketone to form a cyanohydrin (B) through the overall reaction: HO + NaCN + H+ CN +Na+ R R' R R' (B) (A) The mechanism occurs in a (dilute) liquid solution as: 1) Dissociation of the NaCN, which can be considered equilibrated: NaCN Na* + CN 2) Nucleophilic addition of CN to the ketone: A+ CN ACN (anion) (equilibrium constant K:) (forward rate constant k, reverse rate constant k) 3) Protonation: ACN (anion) + H+ B (irreversible, forward rate constant k) The reaction is run in an isothermal continous reactor at 298 K. The values of equilibrium and rate constants at this temperature are given: K = 100 mol/L k = 110 L/mol-min k. = 10 min k = 1000 L/mol-min The volumetric flow rate through the reactor is 10 L/min, and the feed is equimolar in ketone (species A) and NaCN at 0.1 M/L. The inlet pH is 0.5. A 600 L reactor is to be used. Determine whether a 600 L CSTR or 600 L PFR will give a greater fractional conversion, and for whichever will get a higher conversion, determine the outlet concentrations of A, B, and the outlet pH.