Addition/Correction pubs.acs.org/IC
Correction to Understanding the Mechanism of Polymerization of ε‑Caprolactone Catalyzed by Aluminum Salen Complexes Joahanna A. Macaranas, Megan E. Fieser, Anna M. Luke, Mukunda Mandal, Christopher J. Cramer,* and William B. Tolman* Inorg. Chem. 2013, 52 (23), 13692−1370110.1021/ic402255m Page 13693, bottom right, and page 13700, top right. Change “(eq 1)” to “(eq 1, k′ = k2)”. Pages 13694, 13695 and 13700. Refitting the data to eq 1 (k′ = k2/Keq) does not result in significant changes to the reported values of the kinetic and activation parameters, as shown in the new values compiled in the following tables (Tables 1−3 and S1, numbered as they appear in the published work). Most importantly, the trends in these values and the conclusions drawn in the published paper remain unchanged.
In the article in question, we discovered an error in the derivation of the Michaelis−Menten equation using the substrate inhibition mechanism that merits correction, although there are no significant impacts on the conclusions previously drawn from the observed data. In the Supporting Information (p S17), the last step of the derivation requires the following correction: v=
(k 2/Keq)[M − OR′]eq [CL] 1/Keq + [CL]
(S9)
Table 1. Average Values of Kinetic Parameters Determined from COPASI Fits (eq 1, k′ = k2/Keq) and NMR Peak Analysis
This is slightly different from the equation derived for the mechanism involving preequilibrium monomer binding followed by insertion: v=
k 2[M − OR′]eq [CL] 1/Keq + [CL]
Page 13694. Equation 1 should be changed to the following (including the following clarifying text): −
d[CL] d[PCL] k′[2][CL] = = dt dt 1/Keq + [CL]
(1)
where k′ = k2 for the mechanism involving preequilibrium binding followed by insertion and k′ = k2/Keq for the mechanism involving substrate inhibition (vide infra). Page 13698. An additional correction is required for the following statement: “To reconcile the experimentally observed rate law (eq 1) with the absence of such a binding step from the calculated reaction trajectories, we propose a different mechanism involving substrate inhibition (steps enclosed by dashed line in Figure 10, characterized by K′eq and k′2) that yields an experimental rate law indistinguishable from eq 1 (see Supporting Information for derivation). According to this mechanism, reversible substrate binding can be nonproductive, owing to formation of an inactive species.” The corrected statement should read as follows: “To reconcile the experimentally observed rate law (eq 1) with the absence of such a binding step from the calculated reaction trajectories, we propose a different mechanism involving substrate inhibition (steps enclosed by dashed line in Figure 10, characterized by K′eq and k′2) that yields an experimental rate law in the same form, but where k′ = k′2/K′eq (see Supporting Information for derivation). According to this mechanism, reversible substrate binding can be nonproductive, owing to the formation of an inactive species. The rate laws for both mechanisms fit the experimental data equally well, so the pathways cannot be distinguished on the basis of the available data.” © 2013 American Chemical Society
entry
temp (K)
R
Keq COPASI (M−1)
Keq NMR (M−1)
k2 (s−1M−1) (×102)
1 2 3 4 5 6 7 8 9 10 11 12
333 343 353 363 313 323 333 343 293 303 313 323
OMe OMe OMe OMe Br Br Br Br NO2 NO2 NO2 NO2
0.86(6) 0.9(5) 0.66(7) 0.63(7) 1.32(5) 1.13(7) 1.26(3) 1.05(3) 1.3(8) 1.3(1) 1.30(8) 1.22(1)
0.70(5) 0.54(7) 0.56(5) 0.50(7) 0.83(6) 0.8(1) 0.76(4) 0.64(5) 2.2(3) 1.7(2) 1.7(3) 1.5(1)
0.87(9) 1.8(4) 2.90(3) 4.0(5) 1.87(0) 3.0(8) 5.5(9) 8.6(9) 3.4(5) 7.0(3) 11.3(5) 19.5(9)
To reflect effort associated with this Correction, we note that funding was provided by the Center for Sustainable Polymers at the University of Minnesota, a NSF-supported Center for Chemical Innovation (Grant CHE-1413862).
Table 2. Thermodynamic Parameters Associated with Keq for Catalysts 2 Determined by COPASI (Fits to eq 1, k′ = k2/ Keq) and NMR Peak Analysis
A
R
method
ΔH° (kcal/mol)
OMe OMe Br Br NO2 NO2
COPASI NMR COPASI NMR COPASI NMR
−2.5 −2.3 −1.1 −1.8 −0.9 −2.2
± ± ± ± ± ±
0.6 0.5 0.5 0.3 0.6 0.4
ΔS° (cal/mol K) −8 −8 −3 −6 −0.3 −6
± ± ± ± ± ±
2 2 2 1 2 1
ΔG° (kcal/mol, 323 K) −0.01 0.2 −0.1 0.2 −0.8 −0.2
± ± ± ± ± ±
0.8 0.7 0.7 0.5 0.9 0.6
DOI: 10.1021/acs.inorgchem.6b03059 Inorg. Chem. XXXX, XXX, XXX−XXX
Inorganic Chemistry
Addition/Correction
Table 3. Activation Parameters for k2 (eq 1, k′ = k2/Keq) R
ΔH⧧ (kcal/mol)
ΔS⧧ (cal/mol K)
ΔG⧧ (kcal/mol, 323 K)
OMe Br NO2
12.4 ± 0.6 10.6 ± 0.4 10.1 ± 0.3
−31 ± 3 −33 ± 2 −31 ± 2
22 ± 1 21.2 ± 0.9 20.0 ± 0.7
Table S1. Results of COPASI and NMR Analysis of Kinetic Data for the Polymerization of CL entry
temp (K)
R
run no.
Keq COPASI (M−1)a
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
333 333 333 343 343 343 353 353 353 363 363 363 313 313 313 323 323 323 333 333 333 343 343 343 293 293 293 303 303 303 313 313 313 323 323 323
OMe OMe OMe OMe OMe OMe OMe OMe OMe OMe OMe OMe Br Br Br Br Br Br Br Br Br Br Br Br NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2
1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
0.92(9) 0.85(4) 0.81(6) 1.10(3) 0.82(9) 0.91(5) 0.65(3) 0.66(8) 0.68(2) 0.66(0) 0.69(9) 0.55(3) 1.29(6) 1.36(3) 1.31(7) 1.15(1) 1.17(8) 1.08(2) 1.25(2) 1.29(8) 1.24(1) 1.11(2) 1.05(1) 0.99(5) 1.30(6) 1.50(1) 1.33(7) 1.51(2) 1.02(8) 1.37(7) 1.39(1) 1.30(3) 1.23(0) 1.21(6) 1.15(8) 1.28(9)
Keq NMR (M−1)b
0.70(5)
0.54(7)
0.56(5)
0.50(7)
0.83(6)
0.8(1)
0.76(4)
0.64(5)
2.2(3)
1.7(2)
1.7(3)
1.5(1)
k2 (s−1M−1) (×102)a 0.837(5) 0.841(6) 0.957(6) 1.96(8) 1.79(1) 1.77(4) 2.97(2) 2.80(5) 2.93(5) 4.04(3) 4.42(7) 3.68(8) 1.90(3) 1.83(3) 1.87(5) 2.9(9) 3.34(8) 2.88(9) 5.4(1) 5.6(5) 5.69(6) 8.6(2) 8.3(7) 9.0(9) 3.28(7) 3.61(4) 3.46(3) 7.1(7) 6.4(7) 7.4(6) 11.4(1) 11.1(0) 11.5(5) 20.8(1) 18.0(5) 19.8(9)
a
Determined from COPASI analysis of kinetic data (eq 1, k′ = k2/Keq). Note that the errors reported in these values represent the errors in the COPASI fits and, as such, do not reflect the spread of values done in triplicate and are an underestimate of the errors. bAverage of all Keq values determined from the Δδ (NMR) analysis for runs 1−3 at each temperature.
B
DOI: 10.1021/acs.inorgchem.6b03059 Inorg. Chem. XXXX, XXX, XXX−XXX
