Reaction of fluoro(phenyl)carbene with Schiff bases: Synthesis of 2-fluoro-2-phenylaziridines

Article abstract of DOI:10.1007/s11176-005-0480-y

Fluoro(phenyl)carbene generated by reaction of α-bromo-α- fluorotoluene with potassium tert-butoxide reacts with Schiff bases to afford the corresponding 2-fluoro-2-phenylaziridines. The latter were isolated in low yields due to their instability under the carbene generation conditions. Although the reaction of α,α-dibromo-α-fluorotoluene with zinc and lead involves formation of fluoro(phenyl)carbene, this procedure is not suitable for the synthesis of 2-fluoro-2-phenylaziridines. 2005 Pleiades Publishing, Inc.

Full text of DOI:10.1007/s11176-005-0480-y

Russian Journal of General Chemistry, Vol. 75, No. 10, 2005, pp. 1643 1647. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 10, 2005,
pp. 1720 1724.
Original Russian Text Copyright
2005 by Kusei, Novikov, Khlebnikov.
Reaction of Fluoro(phenyl)carbene with Schiff Bases:
Synthesis of 2-Fluoro-2-phenylaziridines
E. Yu. Kusei, M. S. Novikov, and A. F. Khlebnikov
St. Petersburg State University, St. Petersburg, Russia
Received March 11, 2005
Abstract Fluoro(phenyl)carbene generated by reaction of -bromo- -fluorotoluene with potassium tert-
butoxide reacts with Schiff bases to afford the corresponding 2-fluoro-2-phenylaziridines. The latter were
isolated in low yields due to their instability under the carbene generation conditions. Although the reaction of
,
-dibromo- -fluorotoluene with zinc and lead involves formation of fluoro(phenyl)carbene, this procedure
is not suitable for the synthesis of 2-fluoro-2-phenylaziridines.
Aziridines are widely used in the synthesis of
various nitrogen compounds [1 3] and as biologically
active substances [3 5]. Introduction of a fluorine
atom into molecules of pharmacologically active
compounds is known as an efficient tool to enhance
their properties [6]. From this viewpoint, fluorinated
aziridines attract undoubted interest; however, they
still remain difficult to obtain because of the lack of
general procedures for their preparation [7, 8]. A
yield as a result of cyclization of intermediate azo-
methine ylide II (Scheme 1). The steric structure of
aziridine III follows from the coupling constant JHF
which is equal to 2.9 Hz (trans- and cis-coupling
3
constants J for monofluoroaziridine are known to
HF
be 2.4 and 8.1 Hz, respectively [21]). The yield of
aziridine III increased from 9 to 23% on addition of
18-crown-6, presumably due to increased basicity of
the system, which facilitates -elimination of hydro-
promising method for the synthesis of fluorine-contain- gen bromide from -bromo- -fluorotoluene.
ing aziridines is based on the reaction of fluorocar-
benes with Schiff bases, which involves intermediate
formation and intramolecular 1,3-cyclization of un-
stable azomethine ylides. Reactions of chloro(fluoro)-
and bromo(fluoro)carbenes with Schiff bases are
known to produce the corresponding 2-chloro-2-fluoro-
and 2-bromo-2-fluoroaziridines [9 12]. On the other
hand, we failed to use difluorocarbene in reactions
with Schiff bases with a view to obtain 2,2-difluoro-
aziridines: no intramolecular cyclization of inter-
mediate difluoroazomethine to aziridines occurred,
but they underwent other transformations, namely
Scheme 1.
PhCHBrF
t-BuOK
18-crown-6)
(
Ph
Ph
Ph
+
N
Ar
|
..
N
N
:CFPh
.
_
..
Ar
Ar
CFPh
Ph
III
F
I
II
Ar = 4-MeOC H .
6
4
1,3-dipolar cycloaddition, 1,5-cyclization, and ylide
ylide isomerization [13 16]. Fluoro(phenyl)carbene
reacted at the double C=C bond of olefins to give
Probable reasons for the low yield of aziridine III
are both incomplete conversion of Schiff base I and
instability of the product under the given conditions.
By special experiment we showed that heating of
aziridine III in boiling toluene (110 C) in the
presence of potassium tert-butoxide leads to its com-
plete decomposition. Among the decomposition prod-
ducts, we isolated 32% of benzanilide; Scheme 2 il-
lustrates a possible scheme of its formation.
1-fluoro-1-phenylcyclopropanes [17 20], while its
reactions at the C=N bond of Schiff bases were not
studied. In this study we examined the reaction of
fluoro(phenyl)carbene with Schiff bases as a possible
synthetic route to 2-fluoro-2-phenylaziridines.
In the reaction of N-(4-methoxybenzylidene)aniline
(I) with fluoro(phenyl)carbene generated by the action
of potassium tert-butoxide on -bromo- -fluorotolu-
ene at 60 80 C [17 20] we obtained 2-fluoro-3-(4-
methoxyphenyl)-1,2-diphenylaziridine (III) in a poor
The reaction of fluoro(phenyl)carbene with Schiff
base IV afforded compound VII instead of expected
aziridine VI (Scheme 3). Compound VII is likely to
1
070-3632/05/7510-1643 2005 Pleiades Publishing, Inc.

1644
KUSEI et al.
Scheme 2.
Ar
F
Ar
F
Ph
Ph
Ph
Ph
Ar
+
N
+
N
N
H O HN
2
III
..
+
H
F
Ph
Ph
Ph
O
Ph
Ar = 4-MeOC H .
6
4
be formed via cleavage of intermediate aziridine VI
at the C N bond opposite to the carbon atom attached
to fluorine. Such isomerization involving 1,2-migra-
tion of the halogen atom is typical of geminal dihalo-
aziridines. It occurs especially readily with halogen-
containing aziridines having electron-donor substit-
uents at the halogen-free carbon atom in the three-
membered ring [22, 23].
Scheme 3.
Ph
N
Ph
Ar
Ph
N
Ph
+
N
Ph
Ar
F
Ar
Ar
Ar
Ar
Ar
N
+
N
PhCHBrF
Ar
F
Ph
t-BuOK,
18-crown-6
F
Ar
Ph
F
Ph
Ph
IV
V
VI
VII
Ar = 4-MeOC H .
6
4
We succeeded in isolating bicyclic aziridine IX in
the reaction of 6,7-dimethoxy-1-phenyl-3,4-dihydro-
isoquinoline (VIII) with fluoro(phenyl)carbene gene-
rated from -brom- -fluorotoluene by the action of
potassium tert-butoxide in the presence of 18-crown-6
(Scheme 4).
Scheme 4.
O
O
O
PhCHBrF
t-BuOK, 18-crown-6
N
N
Ph
Ph
Ph
F
VIII
IX
The low yields of fluoro(phenyl)aziridines in the
above reactions are determined to a considerable
successfully applied to generate geminal difluoroazo-
methine ylides [15]. Correspondingly, fluoro(phenyl)-
extent by disadvantages intrinsic to the fluoro(phenyl)- carbene could be generated by reduction with metals
carbene generation method used therein, i.e., the
presence of a strong base and elevated temperature.
Therefore, we made an attempt to develop a milder
procedure for generation of fluoro(phenyl)carbene by
analogy with generation of difluorocarbene via reduc-
tion of dibromodifluoromethane with lead or zinc in
the presence of tetrabutylammonium bromide [24].
For example, the reaction of dibromodifluoromethane
with activated lead in the presence of Schiff bases was
of , -dibromo- -fluorotoluene (X). Compound X
was not reported previously. We failed to replace one
bromine atom in , , -tribromotoluene by fluorine
according to Swarts reaction. The desired compound
was synthesized in 64% yield by bromination of
-bromo- -fluorotoluene with bromosuccinimide.
Treatment of compound X with zinc in the presence
of Schiff bases led to formation of ylide reaction
products, while the main products were the corre-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 10 2005

REACTION OF FLUORO(PHENYL)CARBENE WITH SCHIFF BASES:
1645
sponding difluorostilbenes (Scheme 5). In the reaction
of N-benzylidene-N-benzylamine (XI) with , -di-
bromo- -fluorotoluene and zinc we isolated N-benzyl-
benzamide (XII), which was likely to be formed in a
way similar to the formation of benzanilide from
aziridine III.
Scheme 5.
O
PhCBr F
2
F
X
Ph
F
Ph
N
Ph
~~
~
~
Ph
Ph +
~~~
~
N
Zn
H
Ph
XI
XII
H O
2
Ph
Ph
Ph
Ph
Ph
Ph
F
N
Ph
F
+
N
+
N ==
Ph
F
Ph
XIII
A small amount of compound XIV was obtained
in addition to the corresponding difluorostilbenes by
reaction of Schiff base XI with , -dibromo- -fluoro-
toluene and lead in the presence of dimethyl maleate.
A possible scheme of formation of product XIV in-
cludes [3+4]-cycloaddition of ylide XIII to dimethyl
maleate, subsequent recyclization, and hydrolysis
during chromatographic treatment of the reaction
mixture (Scheme 6). No products that could be
formed via [3+2]-cycloaddition of ylide XIII to di-
methyl maleate were detected.
Scheme 6.
Ph
Ph
CO Me
Ph
2
Ph
(
+
)
Ph
(
O
N
N
+
O
:CFPh
CO Me
F
N
2
F
Ph
XI
F
Ph
MeO
Ph
MeO
Ph
CO2Me
CO Me
2
H O,
2
XIII
SiO2
H
N
Ph
Ph
O
Ph
N
N
+
O
MeO C
F
Ph
2
O
F
Ph
Ph
HF
PhCHO,
MeOH
O
Ph
MeO
CO Me
2
Our results show that, although the reaction of , -
dibromo- -fluorotoluene with zinc or lead involves
intermediate formation of fluoro(phenyl)carbene, this
procedure for its generation cannot be used for the
synthesis of 2-fluoro-2-phenylaziridines. The latter
may be obtained via generation of fluoro(phenyl)-
carbene by the action of bases, but instability of
2-fluoro-2-phenylaziridines under these conditions
strongly reduces the efficiency of this approach.
EXPERIMENTAL
The IR spectra were recorded from solutions in
CHCl on a UR-20 spectrometer using 400- m cells.
3
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 10 2005

1646
KUSEI et al.
The NMR spectra were obtained on a Bruker DPX-
N-[2-Fluoro-2,2-bis(4-methoxyphenyl)-1-phenyl-
ethylidene]-N-(2-phenylethyl)amine (VII). To a
solution of 0.6 g of Schiff base IV and 1.3 g of
-bromo- -fluorotoluene in 50 ml of anhydrous to-
luene we added under argon 0.8 g of potassium tert-
butoxide and 30 mg of 18-crown-6. The mixture was
stirred for 2 h at room temperature and filtered
through a 0.5-cm bed of aluminum oxide. The fil-
trate was evaporated, and the residue was recrystal-
lized from diethyl ether to obtain 100 mg (13%) of
compound VII with mp 94 96 C (from diethyl ether).
1
3
00 instrument at 300 MHz for H and 75 MHz for
C. The mass spectra (electron impact, 70 eV) were
1
3
run on an MKh-1303 spectrometer. The elemental
compositions were determined on an HP-185B CHN
analyzer. The progress of reactions was monitored by
TLC on Silufol UV-254 plates. The reaction mixtures
were separated by column chromatography on LS
silica gel (Chemapol, 5 40 m) and basic aluminum
oxide.
-Bromo- -fluorotoluene was synthesized by the
1
1
procedure described in [25]. Activated lead was
prepared according to [15].
IR spectrum (CCl4):
1620 cm , w. H NMR
(C=N)
spectrum (CDCl ), , ppm: 2.91 t (2H, J 7.2 Hz),
3
3
.57 t (2H, J 7.2 Hz), 3.86 s (6H, MeO), 6.70 6.77 m
,
-Dibromo- -fluorotoluene. A mixture of 20 g
(
2H), 6.91 d (4H, J 8.7 Hz), 7.10 7.02 m (2H), 7.24
of -bromo- -fluorotoluene, 22.6 g of N-bromosuc-
cinimide, 0.1 g of azobis(isobutyronitrile), and 100 ml
of carbon tetrachloride was heated for 2 h under reflux.
The mixture was cooled, the precipitate (succinimide)
7
3
1
1
1
.31 m (10H). 13C NMR spectrum (CDCl3), C, ppm:
6.5 (CH ); 54.6 (CH ); 54.9 (OCH ); 100.7 (CF, J
2
2
3
74 Hz); 112.8, 125.7, 126.9, 127.5, 127.7, 127.8,
28.6 d (J 7.0 Hz), 128.8, 132.9 d (J 23.9 Hz), 135.1,
was filtered off and washed with 10 ml of CCl , and
4
39.7, 159.0 (Carom); 172.3 d (C=N, J 35.9 Hz). Mass
the filtrate was washed in succession with a 5% solu-
+
spectrum, m/z (I , %): 453 (3) [M] , 435 (10), 434
rel
tion of Na SO , a 10% solution of Na CO , and water
2
3
2
3
+
(
29) [M
F] , 433 (83), 418 (2), 362 (5) [M
and dried over Na SO with addition of potassium car-
2
4
+
CH Ph] , 344 (12), 343 (23), 342 (100), 326 (9), 311
2
bonate. The solvent was removed, and the residue was
distilled under reduced pressure to isolate 18 g (64%)
(
(
13), 296 (7), 284 (4), 254 (4), 241 (3), 139 (3), 105
21), 91 (7), 77 (7).
of , -dibromo- -fluorotoluene with bp 58 60 C
1
(
7
2 mm). H NMR spectrum (CDCl ), , ppm: 7.40
1-Fluoro-6,7-dimethoxy-1,8b-diphenyl-1,3,4,8b-
3
1
3
.48 m (3H), 7.68 7.71 m (2H). C NMR spectrum
tetrahydroazireno[2,1-a]isoquinoline (IX). To a solu-
tion of 0.7 g of Schiff base VIII and 2.0 g of -bromo-
-fluorotoluene in 50 ml of anhydrous toluene we
added under argon 1.2 g of potassium tert-butoxide
and 35 mg of 18-crown-6. The mixture was stirred for
(
CDCl3), , ppm: 90.4 d (CBr F, J 317.3 Hz); 123.8
C 2
d (J 6.9 Hz), 128.1, 130.3, 144.3 d (J 19.5 Hz)
Carom).
(
2
-Fluoro-3-(4-methoxyphenyl)-1,2-diphenylazi-
2
3
h at 40 C and worked up asdescribed above to isolate
ridine (III). Potassium tert-butoxide, 0.71 g, was
added under argon to a solution of 0.3 g of Schiff base
I and 1.2 g of -bromo- -fluorotoluene in 50 ml of
hexane preliminarily kept over sodium metal. The
mixture was stirred for 12 h at room temperature and
passed through a 0.5-cm bed of basic aluminum
oxide. The sorbent was washed with hexane ethyl
acetate, the solvent was removed, and the residue was
recrystallized from diethyl ether hexane. Yield 40 mg
0 mg (3%) of compound IX with mp 81 84 C (from
1
hexane). H NMR spectrum (CDCl ), , ppm: 2.82
3
3
3
.05 m (2H), 3.54 3.70 m (2H), 3.73 s (3H, MeO),
.90 s (3H, MeO), 6.73 s (1H, Harom), 6.77 s (1H,
13
Harom), 7.16 7.31 m (10H). C NMR spectrum
(
CDCl3), , ppm: 27.6 d (CH , J 3.3 Hz); 40.1 d
C 2
8
b
(CH , J 11.6 Hz); 50.7 d (C , J 22.1 Hz); 55.5
2
(
OCH ); 55.6 (OCH ); 92.8 d (CF, J 255 Hz); 111.0,
3
3
1
1
3
11.8, 123.9, 126.3, 126.5, 126.5 (J 5.0 Hz), 127.2,
27.3, 127.6, 127.8, 128.7 d (J 1.1 Hz), 135.2 d (J
2.1 Hz), 139.2 d (J 2.8 Hz), 147.2, 147.8 (Carom).
(
9%). When the reaction was performed in anhydrous
toluene with addition of 18-crown-6 (5 mol%) at
0 C (reaction time 1 h), the yield of III was 100 mg
23%); mp 93 98 C (decomp., from diethyl ether
7
(
Transformation of aziridine III. A 70-mg portion
1
hexane). H NMR spectrum (CDCl ), , ppm: 3.86 s
of aziridine III was dissolved in 20 ml of anhydrous
toluene, 0.5 g of potassium tert-butoxide and 10 mg
of 18-crown-6 were added, and the mixture was
heated at 120 C. The reaction was accompanied by
strong tarring. The reaction progress was monitored
by TLC. When the initial aziridine disappeared, the
mixture was subjected to column chromatography on
silica gel to isolate 43 mg (32%) of N-phenylbenz-
3
(
7
7
3H, MeO), 3.95 d (1H, JHF 2.9 Hz), 6.79 d (2H, J
.7 Hz), 6.94 7.00 m (3H), 7.12 7.20 m (4H), 7.27
.30 m (3H), 7.56 d (2H, J 7.7 Hz). 13C NMR spec-
trum (CDCl3), C, ppm: 50.2 d (CH, J 13.3 Hz); 55.0
OCH ); 87.1 (CF, J 238 Hz); 113.5, 118.9 d (J
(
3
2
1
1
.2 Hz), 122.5, 125.5 d (J 8.9 Hz), 125.8, 127.8,
28.2, 128.5, 131.6 d (J 29.3 Hz), 145.2 d (J 2.2 Hz),
59.2 (Carom). Found, %: C 79.01; H 5.68; N 4.25.
amide, mp 160 162 C (Et O); published data [26]:
2
C H FNO. Calculated, %: C 78.98; H 5.68; N 4.39.
mp 167 C.
2
1
18
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 10 2005

REACTION OF FLUORO(PHENYL)CARBENE WITH SCHIFF BASES:
1647
Reaction of N-benzylidene-N-benzylamine (XI)
with , -dibromo- -fluorotoluene and lead in the
presence of dimethyl maleate. Anhydrous methylene
chloride, 8 ml, tetrabutylammonium bromide, 1.9 g,
Schiff base XI, 0.38 g, dimethyl maleate, 0.7 g, and
3. Dahanukar, V.H. and Zavialov, I.A., Curr. Opin.
Drug Discovery Dev., 2003, vol. 5, no. 6, p. 918.
4. Brown, F., Vaccine, 2003, vol. 20, nos. 3 4, p. 322.
5. Schirmeister, T. and Klockow, A., Mini-Rev. Med.
Chem., 2003, vol. 3, no. 6, p. 1389.
6. Hiyama, T., Organofluorine Compounds, Berlin:
Springer, 2000.
7. Zeifman, Yu.V. and Lantseva, L.T., Izv. Akad. Nauk
SSSR, Ser. Khim., 1986, no. 1, p. 248.
8. Petrov, V.F., J. Fluorine Chem., 2000, vol. 106,
no. 1, p. 25.
,
-dibromo- -fluorotoluene, 1.55 g, were added in
succession under argon to 1.2 g of activated lead. The
reaction flask was hermetically capped and placed in
an ultrasonic bath. The reaction was carried out at 35
4
5 C, the reaction course being monitored by TLC.
When , -dibromo- -fluorotoluene disappeared com-
pletely, the mixture was subjected to column chro-
matography on silica gel to isolate a mixture of cis-
and trans-difluorostilbenes and 35 mg (5%) of methyl
N-benzyl-2-benzoylsuccinamate (XIV), mp 130
9
. Kostikov, R.R., Khlebnikov, A.F., and Ogloblin, K.A.,
Dokl. Akad. Nauk SSSR, 1975, vol. 223, no. 6,
p. 1375.
1
1
1
0. Yamanaka, H., Kikui, J., Teramura, K., and Ando, T.,
J. Org. Chem., 1976, vol. 41, no. 24, p. 3794.
1. Kostikov, R.R., Khlebnikov, A.F., and Ogloblin, K.A.,
Zh. Org. Khim., 1977, vol. 13, no. 9, p. 1857.
2. Khlebnikov, A.F., Novikov, M.S., Nikiforova, T.Yu.,
and Kostikov, R.R., Zh. Org. Khim., 1999, vol. 35,
no. 1, p. 98.
3. Khlebnikov, A.F., Novikov, M.S., and Kostikov, R.R.,
Mendeleev Commun., 1997, no. 4, p. 145.
4. Khlebnikov, A.F., Novikov, M.S., and Kostikov, R.R.,
Ross. Khim. Zh., 1999, vol. 43, no. 1, p. 70.
5. Novikov, M.S., Khlebnikov, A.F., Sidorina, E.S., and
Kostikov, R.R., J. Chem. Soc., Perkin Trans. 1, 2000,
no. 2, p. 231.
6. Novikov, M.S., Khlebnikov, A.F., and Shevchen-
ko, M.V., J. Fluorine Chem., 2003, vol. 123, no. 2,
p. 177.
7. Moss, R.A., Tetrahedron Lett., 1968, no. 16, p. 1961.
8. Ando, T., Kotoku, Y., Yamanaka, H., and Funasa-
ka, W., Tetrahedron Lett., 1968, no. 20, p. 2479.
9. Moss, R.A. and Przybyla, J.R., Tetrahedron, 1969,
vol. 25, no. 3, p. 647.
1
31 C (from diethyl ether). IR spectrum (CHCl ), ,
3
1
1
cm : 3400 (NH); 1750, 1720, 1700 (C=O). H NMR
spectrum (CDCl ), , ppm: 3.02, 3.23, 4.79 (2H and
3
1
H, CH and CHCO Me, ABX, J 17.2, JAX 8.5,
2 2 AB
JBX 5.9 Hz); 3.67 s (3H, MeO); 4.34, 4.46, 6.36 (2H
and 1H, CH Ph and NH, ABX, JAB 15, JAX 5.8, JBX
2
5
7
.6 Hz); 7.10 7.13 m (2H), 7.25 7.28 m (4H), 7.45
.52 m (2H), 7.60 7.63 m (1H), 8.05 d (2H, J 7.5 Hz).
C NMR spectrum (CDCl3), C, ppm: 33.9 (CH2);
3.4 (CH ); 51.5 (CH ); 51.8 (CH); 127.1, 127.2,
1
1
1
1
3
4
1
1
4
2
3
28.3, 128.4, 128.5, 133.5, 135.7, 137.3 (Carom);
67.2, 171.7, 196.1. Found, %: C 70.23; H 5.85; N
.18. C H NO . Calculated, %: C 70.14; H 5.89;
1
9
19
4
N 4.30.
1
Reaction of N-benzylidene-N-benzylamine (XI)
with , -dibromo- -fluorotoluene and zinc. Schiff
base XI, 1.1 g, , -dibromo- -fluorotoluene, 0.5 g,
and zinc dust, 0.12 g, were added in succession under
stirring to 20 ml of anhydrous tetrahydrofuran. The
reaction flask was hermetically capped and placed in
an ultrasonic bath. The reaction was carried out at 35
1
1
1
2
4
5 C, the reaction course being monitored by TLC.
0. Moss, R.A. and Lawrynowicz, W., J. Org. Chem.,
When , -dibromo- -fluorotoluene disappeared com-
pletely, the mixture was subjected to column chro-
matography on silica gel to isolate 87 mg (22%) of
N-benzylbenzamide, mp 98 100 C (from diethyl
ether); published data [27]: mp 104 C.
1
984, vol. 49, no. 3, p. 3828.
21. Usuki, Y., Fukuda, Y., and Iio, H., ITE Lett. Batter.,
New Technol. Med., 2001, vol. 2, no. 2, p. 237.
22. Kostikov, R.R., Khlebnikov, A.F., and Ogloblin, K.A.,
Khim. Geterotsikl. Soedin., 1978, no. 1, p. 48.
23. Brooks, R.E., Edwards, J.O., Levey, G., and Smyth, F.,
Tetrahedron, 1966, vol. 22, no. 4, p. 1279.
ACKNOWLEDGMENTS
This study was performed under financial support
by the program Universities of Russia (project no.
ur.05.01.316) and by the Russian Foundation for
Basic Research (project no. 05-03-33257).
2
2
2
4. Fritz, H.P. and Kornrupf, W.Z., Z. Naturforsch., B,
981, vol. 36, no. 11, p. 1375.
5. Dneprovskii, A.S. and Eliseenkov, E.V., Zh. Org.
Khim., 1987, vol. 23, no. 4, p. 788.
6. Buzykin, B.I., Sysoeva, L.P., Titova, Z.S., Stolya-
rov, A.P., and Kitaev, Yu.P., Zh. Org. Khim., 1983,
vol. 19, no. 11, p. 2406.
1
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 10 2005