1
490
Can. J. Chem. Vol. 83, 2005
while for primary and secondary halides and sulfonates they
5. (a) G. Wener. US Patent 2 2276 553, 1942; (b) C.F.H. Allen
and P.W. Vittum. US Patent 2 313 498, 1943; (c) G.W.Staton
and F.A. Ehlers. US Patent 2 735 833, 1956; (d) J. Claudim,
J.P. Sisley, and G. Bilger. French Patent 881 458, 1943;
(e) W.D. Stevenson and S. Smiles. J. Chem. Soc. 1740 (1930);
( f ) C.T. Griensheim. German Patent 859 458, 1952; (g) M.F.
Torrence. US Patent 2 658 091, 1953; (h) R.H. Cooper. US
Patent 2 333 468, 1943; (i) T.F Wood and J.H. Garder. J. Am.
Chem. Soc. 63, 2741 (1941).
are ca. –10 cal mol–1
K
–1
(35). For reactions where the
nucleophilic attack of water on a thiocarbonyl is catalyzed
by a second molecule of water, the entropy of activation is
in the –40 to –25 cal mol–1
–1
K
range (36). The value of the
–
1
–1
entropy of activation (–27.3 cal mol K ) for the water ca-
talysis of ETE is consistent with the postulated mechanism,
considering the lack of examples where water catalyzes a re-
action exclusively as a general base. The large value of β =
6
. E. Humeres, L.F. Sequinel, M. Nunes, C.M.S. Oliveira, and
0
.48 obtained from the Brønsted plot suggests that the tran-
P.J. Barrie. J. Phys. Org. Chem. 7, 287 (1994).
sition state is highly polar resulting in electrostriction of the
bulk solvent, inducing a number of water molecules to be
tightly constrained, which results in a large negative entropy
of activation.
7
. A.I. Vogel.
A textbook of practical organic chemistry.
Longmans, London. 1971. p. 499.
8
9
. G. Bulmer and F.G. Mann. J. Chem. Soc. 666 (1945).
. M.C. Rezende. M.Sc. dissertation, Universidade Federal de
Santa Catarina, Florianópolis, Brazil. 1976.
Conclusions
10. K. Horiuti and Y. Kurosu. Tokyo Iji Shinshi, 968 (1940).
1
1
1
1. J.A. Dean (Editor). Lange’s handbook of chemistry. 13th ed.
McGraw Hill, New York. 1985.
2. D.R. Lid (Editor). Handbook of chemistry and physics. 80th
ed. CRC Press, New York. 1999–2000.
3. C.D. Ritchie and J.F. Coetze. Solute–solvent interactions. Mar-
cel Dekker, New York. 1969. Chap. 3.
The acid hydrolysis of ETE at 100 °C occurs through an
A1 mechanism, most likely with N-protonation and forma-
tion of ethylamine by N—C bond breakage, and an ethyl
thionformyl cation (S=C -OEt) that hydrolyzes rapidly to
produce COS and ethanol.
+
At pH 2–6.5, where the main species is the neutral sub-
strate, the hydrolysis is pH-independent and is catalyzed by
water as a general base. General bases catalyze the slow pro-
ton transfer from the neutral species to form an isothio-
cyanate intermediate.
The ETE anion hydrolyzes with specific basic catalysis by
E1cb mechanism, forming ethyl isothiocyanate in the rate-
determining step, which decomposes rapidly to products.
14. (a) E. Humeres, J. Quijano, and M.M.S. de Souza. J. Bras.
Chem. Soc. 1, 99 (1990); (b) E. Humeres, J. Quijano, and
M.M.S. de Souza. Atual. Fis. Quim. Org. Edited by E.
Humeres. IOESC, Florianópolis, Brazil. 1987. p. 198.
15. E.A. Guggenheim. Philos. Mag. 2, 538 (1926).
16. R.A. Cox. Adv. Phys. Org. Chem. 35, 1 (2000).
17. H.S. Harned and R.A. Robinson. Trans. Faraday Soc. 36, 973
(
1940).
8. L. Zucker and L.P. Hammett. J. Am. Chem. Soc. 61, 2791
1939).
9. (a) R.A. Cox. Acc. Chem. Res. 20, 27 (1987); (b) R.A. Cox
and K. Yates. Can. J. Chem. 57, 2944 (1979).
0. (a) A.J. Kresge, R.A. More O’Ferrall, L.E. Hakka, and V.P.
Vitullo. J. Chem. Soc. Chem. Commun. 46 (1965); (b) A.J.
Kresge, S.G. Mylonakis, Y. Sato, and V.P. Vitullo. J. Am.
Chem. Soc. 93, 6181 (1971).
1
1
2
(
Acknowledgements
The scholarship for E.P.de S. and the research fellowship
for E.H. of the Brazilian Conselho Nacional de Pesquisa
Científica e Tecnológica (CNPq) are gratefully acknowledged.
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2005 NRC Canada