Tetrahedron Letters 48 (2007) 7046–7048
Formation of acetaldehyde via photocarbonylation
of methane with CO
a
a
a
a
a
R. Kazimerczuk, T. Wo z´ niewski, M. Borowiak, E. Zimnicka, K. Zwoli n´ ski,
a
b
a
a
a,
*
Z. Rogulski, A. Trzeciak, S. Ostrowski, J. Cz. Dobrowolski and W. Skupi n´ ski
a
Industrial Chemistry Research Institute, Rydygiera 8, 01-793 Warszawa, Poland
Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383 Wrocław, Poland
b
Received 21 March 2007; revised 6 July 2007; accepted 20 July 2007
Available online 27 July 2007
Abstract—Direct photocarbonylation of methane to give acetaldehyde occurred when a mixture of methane and CO dissolved in
benzene was subjected to UV irradiation at k < 290 nm. The reaction was accelerated by rhodium RhCl(CO)(PR ) complexes,
3 2
where R = alkyl, Ph, or OPh.
ꢀ
2007 Published by Elsevier Ltd.
CO insertionintotheC–H bondsofhydrocarbon chainsis
averysimplemethod forthe synthesisofaldehydes. Inves-
tigation of this reaction in the presence of Vaska type
rhodium complexes of general formula RhCl(CO)(PR3)2
ated by the Vaska type rhodium complexes mentioned
above.
The reaction was carried out in a Quartz reactor filled
with a stirred benzene solution saturated with CO and
(
R = alkyl, aryl) resulted in aldehyde formation when
benzene, long-chain alkanes and cyclic alkanes were
CH (10 ml) via irradiation through the reactor wall
4
irradiated with UV light of a wavelength greater than
with a high pressure mercury lamp HOK 400 W—
Phillips. In this way, UV light of the whole spectrum
was introduced to the reaction mixture.
1
3
00 nm.
In the case of methane, direct carbonylation to acetalde-
hydeundernormal pressure occurs as follows(reaction 1):
After running the reaction for 4 h, 0.014 mmol of acetal-
dehyde was obtained (Table 1). This establishes a 0.4%
quantum yield, 0.4% methane conversion and 3.9% con-
CH
4
+ CO!CH
3
CHO
ð1Þ
version of CO (27 mmol of CH and 3.5 mmol of CO
4
4
It is thermodynamically unfavourable—the Gibbs free
energy of the reaction is close to ꢀ15 kcal/mol. As the
calculation indicates, the reaction occurs efficiently
under a pressure of about 4000 atm. Indeed, under these
conditions, acetaldehyde was obtained in the presence of
dissolved in 10 ml of benzene). Beside acetaldehyde, a
trace of benzaldehyde, as the product of benzene car-
bonylation, was present in the post reaction mixture.
To determine which UV light wavelength was responsi-
ble for methane carbonylation, the reaction was carried
out in a Pyrex glass reactor transmitting only UV wave-
ꢁ3
2,3
titanocene catalysts (6.5 · 10 mol/mol Ti).
1
,5
Herein, we report methane carbonylation with CO to
give acetaldehyde, when a mixture of methane and CO
dissolved in benzene was irradiated with UV light of a
wavelength shorter than 290 nm at ambient temperature
under atmospheric pressure. The reaction was acceler-
lengths longer than 290 nm.
under these conditions.
No reaction occurred
To ascertain which irradiation wavelength supports the
carbonylation in the presence of Vaska type rhodium
complex catalysis, the reaction was carried out in Pyrex
and Quartz wall reactors. In the former case, when the
irradiation wavelength was longer than 290 nm, only
benzaldehyde was formed. The largest yield was
obtained for complexes containing alkylphosphines as
Keywords: Methane carbonylation; Acetaldehyde; Rhodium
complexes.
*
0040-4039/$ - see front matter ꢀ 2007 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2007.07.131