Paper
Organic & Biomolecular Chemistry
2010, 75, 4957; (c) F. De Vleeschouwer, V. Van Speybroeck, 23 Both E and N values of all the aldehydes have been calcu-
M. Waroquier, P. Geerlings and F. De Proft, Org. Lett., 2007,
9, 2721; (d) F. Pereira, D. Latino and J. Aires-de-Sousa,
lated in acetonitrile solvent using a PCM model. The N and
E values are given in Table S8 in ESI-1†
J. Org. Chem., 2011, 76, 9312; (e) P. Perez, A. Toro-Labbé, 24 The two equations E (Theo.) = 0.52 × E (Exp.) + 3.09 and
A. Aizman and R. Contreras, J. Org. Chem., 2002, 67, 4747.
11 P. K. Chattaraj, A. Chakraborty and S. Giri, J. Phys. Chem. A,
2009, 113, 10068.
N (Theo.) = −2.73 × N (Exp.) + 1.04 from the
theoretical versus experimental plots have been utilized
for the calculation of N, E and net E values for the
aldehydes.
12 F. C. Tompki, Trans. Faraday Soc., 1943, 39, 280.
13 (a) K. B. Wiberg and R. Stewart, J. Am. Chem. Soc., 1955, 77, 25 (a) The obtained electrophilicities for 5 different aldehydes
1786; (b) R. Stewart, J. Am. Chem. Soc., 1957, 79, 3057;
(c) A. Carrington and M. C. R. Symons, Chem. Rev, 1963, 63,
443.
using this method showed the same trends observed by
Mayr et al. Please see Fig. S7 and Table S9 in ESI-1†;
(b) R. Appel and H. Mayr, J. Am. Chem. Soc., 2011, 133,
8240.
14 J. Tomasi and M. Persico, Chem. Rev., 1994, 94, 2027.
15 The measurement of the activation parameter for 4-nitro 26 R. G. Parr, R. A. Donnelly, M. Levy and W. E. Palke, J. Chem.
benzaldehyde failed because the oxidation reaction was
extremely slow below 298 K.
Phys., 1978, 68, 3801.
27 R. G. Parr and R. G. Pearson, J. Am. Chem. Soc., 1983, 105,
16 H. Eyring, J. Chem. Phys., 1935, 3, 107.
7512.
17 The ΔG# values for NO2 and Br substituted aldehydes 28 R. G. Parr, R. A. Donnelly, M. Levy and W. E. Palke, J. Chem.
in MeCN are high and do not follow the usual gas phase
Phys., 1978, 68, 3801–3807.
trend.
29 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
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18 However, in terms of the correlation coefficient, the plot
between the experimental and theoretical nucleophilicities
of mono, di, and hetero aldehydes combined is slightly
poorer compared to para substituted aldehydes (please see
Fig. S6 in ESI-1†). The author thanks the esteemed reviewer
for raising this point.
19 For the NaBH4 reduction please see: (a) S. W. Chaikin and
W. G. Brown, J. Am. Chem. Soc., 1949, 71, 122;
(b) G. W. Gribble, Chem. Soc. Rev., 1998, 27, 395; and refer-
ences therein.
20 Please see Fig. S2 in ESI-1†
21 The reduction reaction kinetics of aldehydes beyond the
range of 2 to 25 °C is not possible because of the solvent
system and decomposition behavior of NaBH4 at higher
temperatures.
22 It should be noted that while Method I (MI) has been suc-
cessfully utilized for this set of molecules, providing good
correlation between the experimental and computed
results, other methods can also be equally useful to ration-
alize the reactivity for other sets of molecules.
5788 | Org. Biomol. Chem., 2014, 12, 5781–5788
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