Consider the reaction of I^- with CH_3CH_2CI. (i) Would you expect the reaction
ID: 538604 • Letter: C
Question
Consider the reaction of I^- with CH_3CH_2CI. (i) Would you expect the reaction to be S_N1 or S_N2? The rate constant for the reaction at 60 degree C is 5 times 10^-5 L mol^-1 s^-1. (b) What is the reaction rate if [I^-] = 0.1 mol L^-1 and [CH_3CH_2CI] = 0.1 mol L^-1? (c) If [I^-] = 0.1 mol L^-1 and [CH_3CH_2CI] = 0.2 mol L^-1? (d) If [I^-] = 0.2 mol L^-1 and [CH_3CH_2CI] = 0.1 mol L^-1? (e) If [I^-] = 0.2 mol L^-1 and [CH_3CH_2CI] = 0.2 mol L^-1? Which reagent in each pair listed here would be the more reactive nucleophile in a polar solvent? (a) CH_3NH or CH_3NH_2 (b) CH_3O^- or CH_3CO_2^- (-OAc) (c) CH_3SH or CH_3OH (d) (C_6H_5)_3 N or (C_6H_5)_3 P (e) H_2O or H_3O^+ (f) NH_3 or ^+NH_4 (g) H_2S or HS^- (g) CH_3CO_2^- (^-OAc) or HO^-Explanation / Answer
Q. 6.32a) The unit of rate constant of a reaction is Ln-1 mol1-n S-1 where 'n' is the orderof the reaction. From the unit of rate constant wee see that the reaction is second order which indicates that the reaction takes place by SN2 mechanism.
b) Reaction rate, r = k[I-][CH3CH2Cl]
k =5 X 10-5 L mol-1 S-1, [I-] = 0.1 mol L-1, [CH3CH2Cl] = 0.1 mol L-1
Therefore, r = 5 X 10-5 0.1 X 0.1 = 5 X 10-7 mol L-1 S-1
C) k =5 X 10-5 L mol-1 S-1, [I-] = 0.1 mol L-1, [CH3CH2Cl] = 0.2 mol L-1
r = 1 X 10-6 mol L-1
d) k =5 X 10-5 L mol-1 S-1, [I-] = 0.2 mol L-1, [CH3CH2Cl] = 0.1 mol L-1
r = 1 X 10-6 mol L-1
e) k =5 X 10-5 L mol-1 S-1, [I-] = 0.2 mol L-1, [CH3CH2Cl] = 0.2 mol L-1
r = 2 X 10-6 mol L-1
Q. 6.33 Aprotic solvents donot contain -OH groups and cannot form hydrogen bonds. Hence they are good solvents to carry out SN2 reactions. Polar aprotic solvents solvate only cations. Hence the most reactive nucleophile in polar aprotic solvent will be
a) CH3NH-
b) CH3O-
C) CH3SH
d) (C6H5)3P
e) H2O
f) NH3
g) HS-
h) HO-