Cleavage of 4-nitrophenyl diphenyl phosphate by isomeric quaternary pyridinium Ketoximes - How can structure and lipophilicity of functional surfactants influence their reactivity in micelles and microemulsions?

Article abstract of DOI:10.1135/cccc20061642

Amphiphilic pyridinium ketoximes 4-[1-(hydroxyimino)alkyl]-1- methylpyridinium bromides (1) and 1-alkyl-4-[1-(hydroxyimino)ethyl]pyridinium bromides (2) are isomeric cationic surfactants bearing the nucleophilic hydroxyimino group. They differ in the position of the nucleophilic function relative to polar head group and hydrophobic alkyl chain. The 4-nitrophenyl diphenyl phosphate (PNPDPP) cleavage by the oximate anions generated from 1 and 2 was used as a model reaction for the investigation of the influence of the structure and lipophilicity of functional surfactants on their reactivity in micelles and microemulsions. The investigation of the model reaction in cationic micelles of hexadecyltrimethylammonium bromide (CTAB), in non-ionic micelles (Triton X-100 and Brij 35) and in o/w microemulsion (isooctane/phosphate buffer/CTAB and butan-1-ol) has revealed that it is the lipophilicity which is the most important factor influencing the localization and reactivity of functional surfactants in nanoaggregates.

Full text of DOI:10.1135/cccc20061642

1
642
Kivala, Cibulka, Hampl:
CLEAVAGE OF 4-NITROPHENYL DIPHENYL PHOSPHATE BY
ISOMERIC QUATERNARY PYRIDINIUM KETOXIMES –
HOW CAN STRUCTURE AND LIPOPHILICITY OF FUNCTIONAL
SURFACTANTS INFLUENCE THEIR REACTIVITY IN
MICELLES AND MICROEMULSIONS?
1
2
3,
Milan KIVALA , Radek CIBULKA and František HAMPL *
Department of Organic Chemistry, Institute of Chemical Technology, Prague,
1
Technická 5, 166 28 Prague 6, Czech Republic; e-mail: kivala@org.chem.ethz.ch,
2
3
cibulkar@vscht.cz, hamplf@vscht.cz
Received October 10, 2006
Accepted Decem ber 1, 2006
Am ph iph ilic pyridin ium ketoxim es 4-[1-(h ydroxyim in o)alkyl]-1-m eth ylpyridin ium brom ides
1) an d 1-alkyl-4-[1-(h ydroxyim in o)eth yl]pyridin ium brom ides (2) are isom eric cation ic sur-
(
factan ts bearin g th e n ucleoph ilic h ydroxyim in o group. Th ey differ in th e position of th e
n ucleoph ilic fun ction relative to polar h ead group an d h ydroph obic alkyl ch ain . Th e
4
-n itroph en yl diph en yl ph osph ate (PNPDPP) cleavage by th e oxim ate an ion s gen erated from
1
an d 2 was used as a m odel reaction for th e in vestigation of th e in fluen ce of th e structure
an d lipoph ilicity of fun ction al surfactan ts on th eir reactivity in m icelles an d m icro-
em ulsion s. Th e in vestigation of th e m odel reaction in cation ic m icelles of h exadecyl-
trim eth ylam m on ium brom ide (CTAB), in n on -ion ic m icelles (Triton X-100 an d Brij 35) an d
in o/w m icroem ulsion (isooctan e/ph osph ate buffer/CTAB an d butan -1-ol) h as revealed th at
it is th e lipoph ilicity wh ich is th e m ost im portan t factor in fluen cin g th e localization an d re-
activity of fun ction al surfactan ts in n an oaggregates.
Keyw ord s: Fun ction al surfactan ts; Micelles; Microem ulsion s; Nan oaggregates; Pyridin ium
oxim es; Ph osph ate esters cleavage.
In th e recen t decades, various aspects of reactivity of fun ction al surfactan ts
in m icelles, vesicles, an d m icroem ulsion s h ave been in vestigated an d dis-
cussed in h un dreds or rath er th ousan ds of papers an d in m an y books an d
1
reviews . Colloids con tain in g various types of fun ction al surfactan ts an d
m etallosurfactan ts h ave often been con sidered as en zym e m im ics. Am on g
th em , m odels of h ydrolases seem to be of con siderable in terest. Possible ap-
plication s, particularly h ydrolysis of n eurotoxic derivatives of ph osph oric
2
an d ph osph on ic acid h ave stim ulated exten sive research in th is area .
Much effort h as been spen t on attem pts to in crease th e efficien cy of
h ydrolytic catalysts based on m icelles, vesicles, an d m icroem ulsion s con -
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658
©
2006 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc20061642

Cleavage of 4-Nitrophenyl Diphenyl Phosphate
1643
tain in g reactive fun ction al surfactan ts. Th e research h as been focused pre-
1
d,1f
dom in an tly on th e reactive fun ction design
an d on optim ization of
colloid system properties1 . Less atten tion h as been paid to relative posi-
tion an d orien tation of th e reactan ts in m icelles an d vesicles despite th e
fact th at th e restricted m obility of am ph iph ilic m olecules (both tran s-
lation al an d rotation al) can dram atically in fluen ce th eir reactivity in th ese
n an oaggregates. On ly a few studies h ave explored th e relation between th e
reactivity of fun ction al surfactan ts an d probable location an d orien tation
of th eir reactive fun ction in th e n an oaggregate arisin g from th e surfactan t
m olecule sh ape, i.e. from relative position of its polar h ead group, h ydro-
ph obic alkyl ch ain an d reactive fun ction . For exam ple, Ogin o an d cowork-
d,1f
3
ers in vestigated th e h ydrolytic activity of two types of im idazole-based
m etallosurfactan ts in h exadecyltrim eth ylam m on ium brom ide (CTAB) an d
sodium dodecyl sulfate (SDS) m icelles. In th e form er type, th e ch arged group
term in ated th e h ydroph obic ch ain an d th e fun ction al group (2-(h ydroxy-
m eth yl)im idazole m oiety coordin ated to Cu2 ) was in side th e surfactan t
m olecule wh ile in th e latter th e fun ction al group was term in al an d a
ch arged group in side. An oth er exam ple is a series of studies perform ed by
+
4
Rom sted an d coworkers wh o utilized am ph iph ilic aren ediazon ium salts as
probes for th e estim ation of distribution of th e an ion s aroun d cation ic m i-
celles. Th e structures of th e probes em ployed in th ese experim en ts were de-
sign ed to allow th em to take up th e desired position of th e reactive
diazon ium fun ction at th e m icelle/aqueous ph ase in terface.
As a part of our research orien ted to design of poten tial m icellar catalysts
for h ydrolysis of organ oph osph ates, we h ave syn th esized several am ph i-
ph ilic quatern ary pyridin ium ketoxim es an d exam in ed th eir efficien cy in
5
h ydrolysis of 4-n itroph en yl diph en yl ph osph ate (PNPDPP) wh ich is on e of
th e m ost frequen tly used m odels of organ oph osph ate n erve agen ts. Due to
its lipoph ilicity it is reason able to assum e th at PNPDPP is alm ost com -
pletely solubilized in m icellar core. Th e results of kin etic m easurem en ts of
6
th e PNPDPP h ydrolysis in various m icellar an d m etallom icellar system s
were in accord with th is assum ption . We h ave foun d th at th e reactivity of
isom eric pyridin ium ketoxim es 1c an d 2c depen ds on th e position of th eir
n ucleoph ilic h ydroxyim in o fun ction relative to polar h ead group an d h y-
5
a
droph obic alkyl ch ain . Th us, th e apparen t secon d-order rate con stan t k2
of th e PNPDPP cleavage by th e oxim ate an ion form ed from ketoxim e 1c is
h igh er th an th at of th e reaction with th e an ion form ed from its isom er 2c.
We h ave con cluded th at th e observed h igh er reactivity of th e isom er 1c en -
sues from th e fact th at its n ucleoph ilic h ydroxyim in o group is located be-
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

1
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Kivala, Cibulka, Hampl:
low th e m icellar surface th us in creasin g th e probability of th e lipoph ilic
substrate attack as sh own in an idealized ch art (Fig. 1).
FIG. 1
Orien tation of m olecules of surfactan ts 1c an d 2c at m icelle/aqueous ph ase in terface
High efficien cy of th e PNPDPP cleavage by am ph iph ilic ketoxim es 1c an d
2
c in cation ic m icelles of CTAB as well as an in terestin g relation sh ip be-
tween th eir structure an d reactivity to PNPDPP prom pted us to exten d th e
prelim in ary study to h om ologous ketoxim es 1 an d 2 with th e h ydroph obic
alkyls C8–C16, th us coverin g th e in terval of log P values approxim ately
from 1.5 to alm ost 6, an d to oth er n an oaggregates such as n on -ion ic m i-
celles an d o/w m icroem ulsion (partition coefficien t P between octan -1-ol
an d water was used as a gen erally accepted m easure of lipoph ilicity). We as-
sum ed th at th e com parison of th e reactivity of both series of isom eric
ketoxim es 1 an d 2 towards PNPDPP in various colloid system s sh ould per-
m it us to m ake som e gen eral con clusion as far as th e structure of th e fun c-
tion al surfactan t an d its orien tation at th e in terface of th e n an oaggregate is
con cern ed. From th e poin t of view of possible application s, th e fin din g of
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

Cleavage of 4-Nitrophenyl Diphenyl Phosphate
1645
th e optim um type of th e colloid system for h ydrolysis of organ oph osph ates
catalyzed by ketoxim es 1 an d 2 was expected. Just as in our prelim in ary
5
a
study , PNPDPP was used as a m odel substrate with well defin ed localiza-
tion in colloid system s.
RESULTS AND DISCUSSION
Synthesis of Quaternary Pyridinium Ketoximes 1 and 2
4
-[1-(Hydroxyim in o)alkyl]-1-m eth ylpyridin ium brom ides 1 were prepared
5
b
an alogously to th e previously described syn th etic route with th e followin g
exception s: (i) in stead of a Grign ard reagen t, th e correspon din g alkyllith ium
was used in th e preparation of keton es 3a, 3b, an d 3d , (ii) 4-[1-(h ydroxy-
im in o)alkyl]-1-m eth ylpyridin ium brom ides 1 were prepared directly by
quatern ization of th e correspon din g alkyl pyridin -4-yl ketoxim e 4 with
m eth yl brom ide (Sch em e 1). 1-Alkyl-4-[1-(h ydroxyim in o)eth yl]pyridin ium
brom ides 2 were obtain ed by quatern ization of m eth yl 4-pyridin yl
ketoxim e (prepared from com m ercial 4-acetylpyridin e an d h ydroxylam in e)
with th e correspon din g alkyl brom ides.
SCHEME 1
Con figuration at C=N bon d of m eth yl pyridin -4-yl ketoxim e an d oxim e
2
3
4
d was assign ed by NOE experim en ts. Irradiation of H or H arom atic pro-
ton s affords NOE tran sferred to proton of th e h ydroxyim in o group (Fig. 2a)
an d, furth erm ore, irradiation of th e proton of h ydroxyim in o group affords
2
3
NOE to both H an d H arom atic proton s th us givin g eviden ce of Z con fig-
uration . We did n ot observe NOE between α-m eth ylen e proton s of th e alkyl
ch ain an d proton of th e h ydroxyim in o group wh ich sh ould be expected for
(
E)-isom ers (Fig. 2b). In th e case of all oth er alkyl pyridin -4-yl ketoxim es 4,
Z con figuration s was assign ed as well sin ce th e correspon din g h etero-
arom atic proton s sh ifts were practically th e sam e as in th e case of 4d an d
m eth yl pyridin -4-yl ketoxim e. It is kn own th at ch em ical sh ifts of h etero-
arom atic proton s in alkyl pyridin yl ketoxim es are stron gly in fluen ced by
th e C=N bon d con figuration – th e differen ces in ch em ical sh ifts of th e cor-
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

1
646
Kivala, Cibulka, Hampl:
respon din g h eteroarom atic proton s in (E)- an d (Z)-isom ers are up to 0.28
7
ppm . Th e results of NOE experim en ts allowed us to correct th e erron eous
assign m en t of th e con figuration in alkyl pyridin -4-yl ketoxim es stated in
5
b
our previous com m un ication wh ich was don e on th e basis of th e em piri-
8
cal Roberts rule . All th e prepared quatern ary salts 1 an d 2 were of un iform
1
13
con figuration sin ce on ly on e set of sign als was foun d in th eir H an d
C
NMR spectra. We assum e th at th eir con figuration is Z as well sin ce th e
isom erization of th e h ydroxyim in o group is h ardly probable un der th e re-
action con dition s of quatern ization . Th e log P values of PNPDPP an d
ketoxim es 1 an d 2 were calculated usin g a software package Pallas 1.2
9
(
ref. ).
FIG. 2
NOE in teraction s in alkyl pyridin -4-yl ketoxim es: (Z)-isom er (a), (E)-isom er (b)
Micellar Solutions and o/w Microemulsions
Cation ic surfactan t CTAB an d n on -ion ic surfactan ts Triton X-100 an d Brij 35
are th e m ost frequen tly used am ph iph iles for th e preparation of m icellar
1
system s for various kin etic studies an d th erefore we ch ose th em for our ex-
perim en ts as well. Th e resultin g con cen tration of th ese n on -reactive “in ert”
–
2
–1
surfactan ts in th e prepared m icellar solution s (1.0 × 10 m ol l ) suffi-
cien tly exceeded th ose of fun ction al surfactan ts 1 or 2, wh ich ran ged from
–
4
–3
–1
2
.5 × 10 to 2.5 × 10 m ol l . Th erefore we assum ed th at th e properties of
m icellar m atrices in th e correspon din g series of experim en ts were com para-
ble bein g determ in ed by th e in ert surfactan t.
Th e o/w m icroem ulsion type used in our experim en ts was in spired by
Bh attach arya10a. He perform ed kin etic studies of ester h ydrolysis catalyzed
by lipoph ilic supern ucleoph iles in m icroem ulsion s represen tin g pseudo-
tern ary system s con sistin g of ph osph ate buffer (water), cycloh exan e (oil) an d
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

Cleavage of 4-Nitrophenyl Diphenyl Phosphate
1647
CTAB with butan -1-ol wh ich served as a co-surfactan t. In our experim en ts,
we replaced cycloh exan e with less volatile isooctan e. As a “surfactan t” com -
pon en t, we em ployed th e 1:1 m ixture (weigh t ratio) of CTAB an d butan -
–
1
1
-ol an d ph osph ate buffer (0.1 m ol l , pH 7.0) was used as “water”. Th e
pseudo-tern ary system beh aviour was in vestigated poin t-by-poin t by titra-
tion of th e ph osph ate buffer–surfactan t m ixtures with isooctan e. Each com -
position m arked in th e diagram in Fig. 3 represen ts a clear liquid of low
viscosity, isotropic in polarized ligh t, of lon g-term stability. Sin ce th e ph os-
ph ate buffer was a m ajor com pon en t, we classified th ese m icroem ulsion s as
o/w. As eviden t from Fig. 3, th ere exists a relatively large area of com posi-
tion s in wh ich th is pseudotern ary system form s stable o/w m icroem ulsion s.
A question arose wh ich com position from th e area sh own in Fig. 3 is op-
tim al from th e poin t of view of th e m axim um rate of th e PNPDPP cleavage
by ketoxim es 1 an d 2. Sin ce a regular th ree-param eter optim ization of th e
m icroem ulsion com position seem ed to be beyon d th e scope of th is work we
ch ose th e com position on ly on th e basis of th e con sideration s given below.
It was reason able to assum e th at th e con cen tration of reactan ts in th e oil
ph ase (an d, con sequen tly, also th e observed reaction rate) is in versely pro-
1
0
portion al to th e isooctan e con ten t in m icroem ulsion . On th e oth er h an d,
th e in fluen ce of th e surfactan t con ten t was n ot eviden t at th e first sigh t.
FIG. 3
Pseudotern ary system oil (isooctan e)–water (0.1 M ph osph ate buffer, pH 7.0)–surfactan t
(
CTAB/butan -1-ol 1:1) with th e area of o/w m icroem ulsion (᭝). Com position used for kin etic
experim en ts (ꢀ). Outside th e m arked area eith er h eterogen eous system s or lyotropic liquid–crys-
tallin e ph ases were foun d
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

1
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Kivala, Cibulka, Hampl:
Th erefore, we h ave m easured th e depen den ce of th e pseudo-first-order rate
con stan t kobs of th e PNPDPP cleavage by ketoxim es 1 an d 2 on th e sur-
factan t con ten t in m icroem ulsion (Fig. 4). Th e isooctan e con ten t (4%) was
kept con stan t in th ese experim en ts. Th e obtain ed data h ave revealed th at
th e observed reactivity of ketoxim es 1 an d 2 towards PNPDPP is in versely
proportion al to th e surfactan t con ten t in m icroem ulsion as well. Th us, th e
m axim um reaction rate can be expected if both th e oil an d th e surfactan t
con ten t are suppressed to m in im um . Th ese fin din gs led us to ch oose th e
followin g m icroem ulsion com position : isooctan e (4%), ph osph ate buffer
pH 7.0 (86%), CTAB (5%) an d butan -1-ol (5%).
Reactivity of Ketoximes 1 and 2 in Micellar Solutions and
o/w Microemulsions
It is well recogn ized th at th e regression an alysis of absorban ce (or an y oth er
m acroscopic quan tity givin g eviden ce of th e reaction course) vs tim e data
affords th e apparen t rate con stan t on ly, wh ich is an average value calcu-
lated for th e total reaction system volum e if th e reaction is carried out in
h eterogen eous system s. Th erefore, th e apparen t secon d-order rate con stan t
k2 values correspon d to real reaction rates n eith er in m icellar pseudoph ase
n or in m icroem ulsion oil ph ase wh ere th e local m olarities of lipoph ilic re-
FIG. 4
Depen den ce of th e pseudo-first-order rate con stan t kobs of th e PNPDPP cleavage by ketoxim es
1
4
(᭿) an d 2 (ꢀ) on th e surfactan t (CTAB/1-butan ol 1:1) con ten t in m icroem ulsion s con tain in g
% of isooctane. Conditions: [1] = [2] = 1.0 × 10 mol l , [PNPDPP] = 2.0 × 10 mol l , T = 25 °C
–3
–1
–5
–1
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

Cleavage of 4-Nitrophenyl Diphenyl Phosphate
1649
actan ts are substan tially h igh er com pared with an alytical (average) con cen -
1
1
tration s . Neverth eless, th is particular fact brin gs th e advan tage of im plicit
in form ation on th e con cen tration of reactan ts in colloid particles an d on
oth er circum stan ces in fluen cin g th e reaction rate such as availability of th e
reactan ts an d th eir relative orien tation in colloid particles.
Th e obtain ed results of th e PNPDPP cleavage by ketoxim es 1 an d 2 in
m icelles an d o/w m icroem ulsion are sum m arized in Fig. 5. Regardless
of th e type of m icellar system , th e reactivity of both types of pyridin ium
ketoxim es in creases with th eir lipoph ilicity. Th is tren d is n ot surprisin g
sin ce m ore lipoph ilic com poun ds are m ore tigh tly boun d by th e n an o-
1
a,12
12,13
aggregates
. Accordin g to gen erally accepted opin ion
, cation ic m i-
celles in crease th e rate of alkalin e h ydrolysis due to th e positive ch arge of
th e m icellar surface wh ich in creases th e local pH value. In deed, th e reactiv-
ity of ketoxim es 1 an d 2 in CTAB m icelles was th e h igh est in th e in vesti-
gated system s.
Th e observed reactivity of ketoxim es 1 an d 2 in o/w m icroem ulsion s is
m uch lower com pared with m icellar solution s. Th is fact is n ot surprisin g
sin ce th e con cen tration s of th e reactan ts in oil ph ases of m icroem ulsion s
1
0
are usually lower com pared with th ose in m icellar ph ase . Micellar ph ase
–
2
in 1.0 × 10 M CTAB m akes ca. 0.4% of th e total solution volum e in volvin g
th e assum ption th at m olar volum e of m icellized CTAB in aqueous solution s
FIG. 5
Depen den ce of th e secon d-order rate con stan t k2 of th e PNPDPP cleavage by ketoxim es 1 (full
sym bols) an d 2 (open sym bols) on th eir lipoph ilicity (log P) in differen t types of aggregates:
CTAB (᭿, ᮀ), Triton X-100 (᭹, ᭺), Brij 35 (ꢀ, ᭝), an d o/w m icroem ulsion (᭢, ᭞). Th e lin es
h elp th e eyes to follow th e data poin ts.
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

1
650
Kivala, Cibulka, Hampl:
is 0.37 l m ol–1 (ref. ). On the other hand, in m icroem ulsions em ployed in our
kin etic experim en ts th e oil ph ase fraction m ade ca. 6% of th e total volum e.
Th e reactivity of ketoxim es 2 in o/w m icroem ulsion in creases with th eir
lipoph ilicity alth ough th is tren d is m uch less pron oun ced com pared with
m icellar solution s. Th e reactivity of ketoxim es 1 is practically un affected by
th eir lipoph ilicity. We assum e th at a h igh er proportion of th e organ ic
ph ase in o/w m icroem ulsion s in creases th e efficien cy of th e extraction of
ketoxim es 1 an d 2 in to colloid particles in com parison with m icelles th us
dim in ish in g th e effect of in creasin g lipoph ilicity.
14
At first sigh t, th e in fluen ce of th e structure of ketoxim es 1 an d 2 on th eir
reactivity in m icelles an d o/w m icroem ulsion is n ot obvious from th e
secon d-order rate con stan ts k values given in Fig. 5. A better in form ation
2
on th e beh aviour of isom eric ketoxim es 1 an d 2 in n an oaggregates affords
com parison of th e reactivity of th e correspon din g h om ologues (Fig. 6). On
goin g from C8 to C16 h om ologues, th e ratio of secon d-order rate con stan ts
(
k ) /(k ) for ketoxim es 1 an d 2 of th e sam e h ydroph obic alkyl ch ain
2 1 2 2
len gth (an d practically th e sam e lipoph ilicity) decreases in all types of th e
exam in ed n an oaggregates con vergin g to un ity for C16. In oth er words, th e
differen ce in th e reactivity of both isom eric ketoxim es 1 an d 2 practically
disappears in th e case of sufficien tly lipoph ilic h om ologues.
FIG. 6
Depen den ce of th e ratio of secon d-order rate con stan ts (k ) /(k ) for th e correspon din g h om o-
2
1
2 2
logues of ketoxim es 1 an d 2 on th e h ydroph obic alkyl ch ain len gth in various types of aggre-
gates: CTAB (ᮀ), Triton X-100 (᭺), Brij 35 (᭝), an d o/w m icroem ulsion (᭞). Th e lin es h elp th e
eyes to follow th e data poin ts
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

Cleavage of 4-Nitrophenyl Diphenyl Phosphate
1651
Most likely, less lipoph ilic ketoxim es 1 an d 2 prefer to set at th e boun d-
ary of th e n an oaggregate with th e orien tation depicted in Fig. 1 as reported
5
a
previously . On th e oth er h an d, m ore lipoph ilic surfactan ts (log P > 4 in
th is particular case) are pron e, regardless of th eir structure, to leave th e in -
terface an d react in th e in terior of th e n an oaggregate. Th us, con trary to our
5
a
previous h ypoth esis , th e lipoph ilicity of th e fun ction al surfactan t seem s
to be a m ore im portan t factor in fluen cin g its reactivity in an y m icellar sys-
tem in vestigated th an its structure i.e. m utual position of th e polar h ead
group, h ydroph obic alkyl ch ain an d fun ction al group. As sh own in an ide-
alized ch art in Fig. 7, th e in fluen ce of lipoph ilicity is even capable to over-
com e th e in fluen ce of th e structure differen ces in th e case of isom eric
fun ction al surfactan ts 1 an d 2. Th e close resem blan ce of th e plots of th e
relative reactivity of ketoxim es 1 an d 2 in m icelles vs h ydroph obic ch ain
len gth (Fig. 6) supports th is h ypoth esis. Th e discussed beh avior observed in
m icelles is less pron oun ced in th e o/w m icroem ulsion for th e reason s m en -
tion ed above.
FIG. 7
Sch em atic illustration explain in g th e reactivity of am ph iph ilic ketoxim es 1 an d 2 in n an o-
aggregates
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

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Kivala, Cibulka, Hampl:
Conclusion
Alth ough exam in ed in th e case of isom eric pyridin ium ketoxim es 1 an d 2
on ly, it is reason able to assum e th at th e above discussed prin ciples are ap-
plicable to assessm en t of th e reactivity of an y fun ction al surfactan t in
n an oaggregates an d sh ould be taken in to con sideration in th e design of
an y m icellar catalyst an d optim ization of its efficien cy.
EXPERIMENTAL
Gen eral
Meltin g poin ts were un corrected. 1H an d
13
C NMR spectra were recorded on a Varian
1
13
Gem in i 300 (operatin g at 300.1 an d 75.1 MHz for H an d C, respectively) or on a Bruker
AMX3 400 (operatin g at 400.1 an d 100.6 MHz for 1H an d C, respectively). Ch em ical sh ifts
13
(
δ, ppm ) are reported relative to in tern al Me Si. All couplin g con stan ts (J) are in Hz. TLC
4
an alyses were carried out on DC Alufolien Kieselgel 60 F254. Preparative colum n ch rom atog-
raph y was perform ed on silica gel 60, 0.040–0.063 m m .
Ch em icals
All th e ch em icals used in th e syn th eses (quality purum or pract.) were used as received. Th e
1
5
solven ts were purified an d dried accordin g to described procedures . Hexadecyltrim eth yl-
am m on ium brom ide (CTAB) puriss., isooctan e for HPLC (n ot less th an 99.5%), an d Brij 35
were obtain ed from Aldrich , Triton X-100 from Fluka. Butan -1-ol an d oth er ch em icals an d
m aterials (puriss.) were supplied by Lach em a. 4-Nitroph en yl diph en yl ph osph ate (PNPDPP)
1
6
was prepared an d purified accordin g to th e described procedure . Th e o/w m icroem ulsion
for th e kin etic experim en ts was prepared by vigorous m ixin g of a m ixture of 0.1 M ph os-
ph ate buffer, pH 7.0 (86 wt.%), isooctan e (4 wt.%), CTAB (5 wt.%), an d butan -1-ol (5 wt.%)
at am bien t tem perature. Th e resultin g o/w m icroem ulsion (clear liquid of low viscosity, iso-
tropic in polarized ligh t, pH 7.0) was stable for m on th s.
Alkyl Pyridin -4-yl Keton es 3. Gen eral Procedure
A solution of alkyllith ium 17 (ca. 0.2 m ol l–1; 0.091 m ol) in eth er or a 1 M solution of dodecyl-
m agn esium brom ide in eth er was added dropwise at –30 °C to a solution of pyridin e-
4
-carbon itrile (0.091 m ol) in eth er (450 m l) with in 1 h . After 1 h stirrin g at –10 °C an d
warm in g-up to room tem perature th e reaction m ixture was quen ch ed with 2 M h ydroch lo-
ride acid. pH of th e m ixture was adjusted to 8 with potassium carbon ate. Th e organ ic layer
was separated, th e aqueous solution was extracted with eth er (5 × 150 m l) an d th e com -
bin ed organ ic layers were dried with an h ydrous m agn esium sulfate. Evaporation of th e sol-
ven t afforded crude product wh ich was purified by colum n ch rom atograph y (ch loroform –
m eth an ol 100:3).
Octyl pyridin-4-yl ketone (3a). Yield 72.2%. Wh ite crystals, m .p. 37.5–39 °C. 1H NMR
(
CDCl ): 0.81 t, 3 H, J(8′,7′) = 6.6 (CH ); 1.21 bs, 10 H ((CH ) ); 1.67 tt, 2 H, J(2′,1′) = J(2′,3′) =
3 3 2 5
7
.3 (CH CH C=O); 2.89 t, 2 H, J(1′,2′) = 7.3 (CH C=O); 7.65 dd, 2 H, J(3,2) = J(5,6) = 4.4,
2
2
2
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

Cleavage of 4-Nitrophenyl Diphenyl Phosphate
1653
J(3,5) = J(5,3) = 1.5 (H-3, H-5); 8.73 d, 2 H, J(2,3) = J(6,5) = 5.3 (H-2, H-6). 13C NMR (CDCl ):
3
1
3
4.3 s (CH ); 22.9 s (CH CH ); 24.1 s (CH CH CH ); 29.5 t ((CH ) ); 32.0 s (CH CH C=O);
3 2 3 2 2 3 2 3 2 2
9.1 s (CH C=O); 121.3 s (C-3, C-5); 143.1 s (C-4); 151.2 s (C-2, C-6); 200.1 s (C=O). For
2
C14H21NO (219.3) calculated: 76.67% C, 9.65% H, 6.39% N; foun d: 76.62% C, 10.29% H,
6
.33% N.
Decyl pyridin-4-yl ketone (3b ). Yield 92.9%. Wh ite crystals, m .p. 51–52.5 °C. 1H NMR
(
CDCl ): 0.81 t, 3 H, J(10′,9′) = 6.6 (CH ); 1.20 bs, 14 H ((CH ) ); 1.66 tt, 2 H, J(2′,1′) =
3 3 2 7
J(2′,3′) = 7.3 (CH CH C=O); 2.89 t, 2 H, J(1′,2′) = 7.3 (CH C=O); 7.65 dd, 2 H, J(3,2) = J(5,6) =
2
2
2
4
.4, J(3,5) = J(5,3) = 1.7 (H-3, H-5); 8.73 dd, 2 H, J(2,3) = J(6,5) = 4.4, J(2,6) = J(6,2) = 1.7
(
(
(
H-2, H-6). 13C NMR (CDCl ): 14.3 s (CH ); 22.9 s (CH CH ); 24.1 s (CH CH CH ); 29.6 m
3
3
2
3
2
2
3
(CH ) ); 32.1 s (CH CH C=O); 39.1 s (CH C=O); 121.3 s (C-3, C-5); 143.1 s (C-4); 151.2 s
C-2, C-6); 200.1 s (C=O). For C16H25NO (247.4) calculated: 77.68% C, 10.19% H, 5.66% N;
2
5
2
2
2
foun d: 77.38% C, 10.20% H, 5.60% N.
Dodecyl pyridin-4-yl ketone (3c). Yield 66.5%. Wh ite crystals, m .p. 55–60 °C (ref.5b 56–60 °C).
1
H NMR (CDCl ): 0.87 t, 3 H, J(12′,11′) = 6.7 (CH ); 1.25 bs, 18 H ((CH ) ); 1.73 tt, 2 H,
3
3
2 9
J(2′,1′) = J(2′,3′) = 7.3 (CH CH C=O); 2.95 t, 2 H, J(1′,2′) = 7.3 (CH C=O); 7.72 dd, 2 H, J(3,2) =
2
2
2
J(5,6) = 4.4, J(3,5) = J(5,3) = 1.8 (H-3, H-5); 8.80 dd, 2 H, J(2,3) = J(6,5) = 4.4, J(2,6) = J(6,2) =
1
3
1
.8 (H-2, H-6). C NMR (CDCl ): 14.3 s (CH ); 22.9 s (CH CH ); 24.1 s (CH CH CH ); 29.7 m
3 3 2 3 2 2 3
(
(
(CH ) ); 32.1 s (CH CH C=O); 39.1 s (CH C=O); 121.3 s (C-3, C-5); 143.1 s (C-4); 151.2 s
2 7 2 2 2
C-2, C-6); 200.1 s (C=O). For C18H29NO (275.4) calculated: 78.49% C, 10.61% H, 5.09% N;
foun d: 78.23% C, 10.49% H, 4.90% N.
Hexadecyl pyridin-4-yl ketone (3d ). Yield 78.5%. Wh ite crystals, m .p. 71–75 °C. 1H NMR
(
CDCl ): 0.87 t, 3 H, J(16′,15′) = 6.6 (CH ); 1.28 bs, 26 H ((CH )13); 1.73 tt, 2 H, J(2′,1′) =
3 3 2
J(2′,3′) = 7.3 (CH CH C=O); 2.95 t, 2 H, J(1′,2′) = 7.3 (CH C=O); 7.72 dd, 2 H, J(3,2) = J(5,6) =
2
2
2
4
.5, J(3,5) = J(5,3) = 1.5 (H-3, H-5); 8.80 dd, 2 H, J(2,3) = J(6,5) = 4.5, J(2,6) = J(6,2) = 1.5
(
(
(
H-2, H-6). 13C NMR (CDCl ): 14.3 s (CH ); 22.9 s (CH CH ); 24.1 s (CH CH CH ); 29.7 m
3
3
2
3
2
2
3
(CH2)11); 32.1 s (CH CH C=O); 39.1 s (CH C=O); 121.3 s (C-3, C-5); 143.0 s (C-4); 151.2 s
C-2, C-6); 200.0 s (C=O). For C22H37NO (331.6) calculated: 79.70% C, 11.25% H, 4.22% N;
2
2
2
foun d: 80.03% C, 11.60% H, 4.10% N.
Alkyl Pyridin -4-yl Ketoxim es 4. Gen eral Procedure
Aqueous solution of h ydroxylam in e (50%; 0.329 m ol) was added in two portion s to th e boil-
in g solution of keton e 3 (0.065 m ol) in m eth an ol (200 m l) with in 14 h . Evaporation of sol-
ven t gave crude product, wh ich was purified by colum n ch rom atograph y (ch loroform –
m eth an ol 100:6). Th e described procedure afforded alm ost pure (>95%) (Z)-isom ers of 4a
an d 4b. In th e case of ketoxim es 4c an d 4d , th e Z/E ratio was 11:1 an d 9:1, respectively.
Pure (Z)-4c an d (Z)-4d were obtain ed by crystallization from aqueous eth an ol.
(
Z)-Octyl pyridin-4-yl ketoxime (4a). Yield 80.5%. Wh ite crystals, m .p. 85–90 °C. 1H NMR
CDCl ): 0.86 t, 3 H, J(8′,7′) = 6.2 (CH ); 1.25 bs, 10 H ((CH ) ); 1.56 tt, 2 H, J(2′,1′) = J(2′,3′) =
(
3
3
2 5
7
.4 (CH CH C=O); 2.80 t, 2 H, J(1′,2′) = 7.3 (CH C=O); 7.59 dd, 2 H, J(3,2) = J(5,6) = 4.7,
2 2 2
J(3,5) = J(5,3) = 1.4 (H-3, H-5); 8.64 dd, 2 H, J(2,3) = J(6,5) = 4.7, J(2,6) = J(6,2) = 1.7 (H-2,
1
3
H-6); 11.75 s, 1 H (OH).
C NMR (CDCl ): 14.3 s (CH ); 22.9 s (CH CH ); 25.5 s
3 3 2 3
(
(
CH CH CH ); 26.5 s (CH (CH ) CH ); 29.5 d ((CH ) ); 30.1 s (CH CH C=NOH); 32.0 s
2 2 3 2 2 2 3 2 2 2 2
CH C=NOH); 120.9 s (C-3, C-5); 144.4 s (C-4); 149.9 s (C-2, C-6); 157.2 s (C=NOH). For
2
C14H22N O (234.3) calculated: 71.76% C, 9.46% H, 11.95% N; foun d: 72.40% C, 9.69% H,
2
1
2.03% N.
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

1
654
Kivala, Cibulka, Hampl:
(
Z)-Decyl pyridin-4-yl ketoxime (4b). Yield 65.4%. Wh ite crystals, m .p. 88–91.5 °C. 1H NMR
CDCl ): 0.80 t, 3 H, J(10′,9′) = 6.5 (CH ); 1.22 bs, 14 H ((CH ) ); 1.49 tt, 2 H, J(2′,1′) =
(
3
3
2 7
J(2′,3′) = 7.3 (CH CH C=NOH); 2.72 t, 2 H, J(1′,2′) = 7.9 (CH C=NOH); 7.65 d, 2 H, J(3,2) =
2
2
2
J(5,6) = 6.1 (H-3, H-5); 8.57 d, 2 H, J(2,3) = J(6,5) = 6.2 (H-2, H-6); 9.77 s, 1 H (OH).
1
3
C
NMR (CDCl ): 14.3 s (CH ); 22.9 s (CH CH ); 25.5 s (CH CH CH ); 26.5 s
3 3 2 3 2 2 3
(
(
CH (CH ) CH ); 29.7 m ((CH ) ); 30.0 s, (CH CH C=NOH); 32.1 s (CH C=NOH); 120.9 s
2 2 2 3 2 4 2 2 2
C-3, C-5); 144.3 s (C-4); 149.9 s (C-2, C-6); 157.6 s (C=NOH). For C16H26N O (262.4) calcu-
2
lated: 73.24% C, 9.99% H, 10.68% N; foun d: 73.27% C, 10.06% H, 10.59% N.
Z)-Dodecyl pyridin-4-yl ketoxime (4c). Yield 73.8%. Wh ite crystals, m .p. 91–95 °C (ref.
5
b
(
1
9
1
7
6
2–94 °C). H NMR (CDCl ): 0.87 t, 3 H, J(12′,11′) = 6.5 (CH ); 1.24 bs, 18 H ((CH ) );
3 3 2 9
.55 tt, 2 H, J(2′,1′) = J(2′,3′) = 7.7 (CH CH C=NOH); 2.78 t, 2 H, J(1′,2′) = 7.9 (CH C=NOH);
2
2
2
.54 dd, 2 H, J(3,2) = J(5,6) = 5.4, J(3,5) = J(5,3) = 0.9 (H-3, H-5); 8.63 d, 2 H, J(2,3) = J(6,5) =
1
3
.2 (H-2, H-6); 10.25 s, 1 H (OH). C NMR (CDCl ): 14.3 s (CH ); 22.9 s (CH CH ); 25.5 s
3
3
2
3
(
CH CH CH ); 26.0 s (CH (CH ) CH ); 26.5 s (CH (CH ) CH ); 29.8 m ((CH ) ); 32.1 s
2 2 3 2 2 2 3 2 2 3 3 2 5
(
CH CH C=NOH); 33.0 s (CH C=NOH); 120.8 s (C-3, C-5); 144.3 s (C-4); 150.0 s (C-2, C-6);
2 2 2
1
7
57.4 s (C=NOH). For C18H30N O (290.5) calculated: 74.44% C, 10.41% H, 9.64% N; foun d:
4.15% C, 10.58% H, 9.52% N.
2
(
Z)-Hexadecyl pyridin-4-yl ketoxime (4d ). Yield 84.4%. Wh ite crystals, m .p. 94–96.5 °C.
1
H NMR (CDCl ): 0.87 t, 3 H, J(16′,15′) = 6.7 (CH ); 1.24 bs, 26 H ((CH )13); 1.55 tt, 2 H,
3
3
2
J(2′,1′) = J(2′,3′) = 7.5 (CH CH C=NOH); 2.78 t, 2 H, J(1′,2′) = 7.7 (CH C=NOH); 7.53 dd,
2
2
2
2
H, J(3,2) = J(5,6) = 4.9, J(3,5) = J(5,3) = 1.4 (H-3, H-5); 8.63 dd, 2 H, J(2,3) = J(6,5) = 4.8,
1
3
J(2,6) = J(6,2) = 1.4 (H-2, H-6); 9.09 s, 1 H (OH). C NMR (CDCl ): 14.3 s (CH ); 22.9 s
3
3
(
(
CH CH ); 25.5
s
(CH CH CH ); 26.5
s
(CH (CH ) CH ); 29.8
m
((CH2)11); 32.1 s
2
3
2
2
3
2
2
2
3
CH C=NOH); 120.8 s (C-3, C-5); 143.9 s (C-4); 150.2 s (C-2, C-6); 157.9 s (C=NOH). For
2
C22H38N O (346.6) calculated: 76.25% C, 11.05% H, 8.08% N; foun d: 76.18% C, 11.33% H,
2
7
.80% N.
4
-[1-(Hydroxyim in o)alkyl]-1-m eth ylpyridin ium Brom ides 1. Gen eral Procedure
A solution of oxim e 4 (0.047 m ol) an d m eth yl brom ide (0.5 m ol) in m eth an ol (100 m l) was
stirred at 45 °C for 15 h un der a cold-fin ger reflux con den ser cooled with eth an ol–CO (s).
2
Th en , th e solven t with th e un reacted m eth yl brom ide were evaporated an d th e rem ain in g
crude product was purified by colum n ch rom atograph y (ch loroform –m eth an ol–aceton e–
water 15:5:5:1) followed by crystallization from th e m ixture aceton e–dieth yl eth er. All th e
prepared quatern ary oxim es were of un iform con figuration sin ce on ly on e set of sign als was
1
13
foun d in th eir H or C NMR spectra. It is eviden t th at th e con figuration of th e quatern ary
salts 1 is th e sam e as in oxim es 4.
4
-[1-(Hydroxyimino)nonyl]-1-methylpyridinium bromide (1a). Yield 69.2%. M.p. 147–151 °C.
1
H NMR (DMSO-d ): 0.82 t, 3 H, J(8′,7′) = 6.6 (CH ); 1.20 bs, 10 H ((CH ) ); 1.40 m , 2 H
6
3
2 5
+
(
CH CH C=NOH); 2.78 t, 2 H, J(1′,2′) = 7.4 (CH C=NOH); 4.29 s, 3 H (CH -N ); 8.26 d, 2 H,
2 2 2 3
J(3,2) = J(5,6) = 6.6 (H-3, H-5); 8.90 d, 2 H, J(2,3) = J(6,5) = 6.8 (H-2, H-6); 12.59 s, 1 H (OH).
1
3
C
NMR (DMSO-d ): 14.6 s (CH ); 22.7 s (CH CH ); 24.5 s (CH CH CH ); 26.1 s
6 3 2 3 2 2 3
(
(
CH (CH ) CH ); 29.3 d ((CH ) ); 29.7 s (CH CH C=NOH); 31.9 s (CH C=NOH); 48.0 s
2 2 2 3 2 2 2 2 2
+
CH -N ); 123.9 s (C-3, C-5); 146.3 (C-2, C-6); 151.2 s (C-4); 154.7 s (C=NOH). For
3
C15H25BrN O (329.3) calculated: 54.71% C, 7.65% H, 8.51% N; foun d: 54.66% C, 8.26% H,
2
8
.69% N.
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

Cleavage of 4-Nitrophenyl Diphenyl Phosphate
1655
4
-[1-(Hydroxyimino)undecyl]-1-methylpyridinium bromide (1b). Yield 70.7%. M.p. 134–137 °C.
1
H NMR (DMSO-d ): 0.82 t, 3 H, J(10′,9′) = 6.7 (CH ); 1.20 bs, 10 H ((CH ) ); 1.40 m , 2 H
6
3
2 5
+
(
CH CH C=NOH); 2.78 t, 2 H, J(1′,2′) = 7.6 (CH C=NOH); 4.31 s, 3 H (CH -N ); 8.26 d, 2 H,
2 2 2 3
J(3,2) = J(5,6) = 6.9 (H-3, H-5); 8.93 d, 2 H, J(2,3) = J(6,5) = 6.6 (H-2, H-6); 12.56 s, 1 H (OH).
1
3
C
NMR (DMSO-d ): 14.6 s (CH ); 22.8 s (CH CH ); 24.5 s (CH CH CH ); 26.2 s
6 3 2 3 2 2 3
+
(
CH (CH ) CH ); 29.5 m ((CH ) ); 32.0 s (CH C=NOH); 48.0 s (CH -N ); 123.9 s (C-3, C-5);
2 2 2 3 2 5 2 3
1
5
46.3 s (C-2, C-6); 151.1 s (C-4); 154.7 s (C=NOH). For C17H29BrN O (357.3) calculated:
7.14% C, 8.18% H, 7.84% N; foun d: 57.11% C, 8.25% H, 7.88% N.
2
4
-[1-(Hydroxyimino)tridecyl]-1-methylpyridinium bromide (1c). Yield 53.5%. M.p. 122–125 °C.
1
H NMR (DMSO-d ): 0.82 t, 3 H, J(12′,11′) = 6.6 (CH ); 1.20 bs, 18 H ((CH ) ); 1.40 m , 2 H
6
3
2 9
+
(
CH CH C=NOH); 2.78 t, 2 H, J(1′,2′) = 7.4 (CH C=NOH); 4.30 s, 3 H (CH -N ); 8.26 d, 2 H,
2 2 2 3
J(3,2) = J(5,6) = 6.9 (H-3, H-5); 8.92 d, 2 H, J(2,3) = J(6,5) = 6.9 (H-2, H-6); 12.59 s, 1 H (OH).
1
3
C
NMR (DMSO-d ): 14.6 s (CH ); 22.8 s (CH CH ); 24.5 s (CH CH CH ); 26.2 s
6 3 2 3 2 2 3
+
(
CH (CH ) CH ); 29.5 m ((CH ) ); 32.0 s (CH C=NOH); 48.0 s (CH -N ); 123.9 s (C-3, C-5);
2 2 2 3 2 7 2 3
1
5
46.3 s (C-2, C-6); 151.2 s (C- 4); 154.7 s (C=NOH). For C19H33BrN O (385.4) calculated:
9.22% C, 8.63% H, 7.27% N; foun d: 59.01% C, 8.65% H, 7.00% N.
2
4
-[1-(Hydroxyimino)heptadecyl]-1-methylpyridinium bromide (1d). Yield 68.1%. M.p. 124–126 °C.
1
H NMR (DMSO-d ): 0.82 t, 3 H, J(16′,15′) = 6.3 (CH ); 1.20 bs, 26 H ((CH ) ); 1.40 m , 2 H
6
3
2 13
+
(
CH CH C=NOH); 2.78 t, 2 H, J(1′,2′) = 7.4 (CH C=NOH); 4.30 s, 3 H (CH -N ); 8.26 d, 2 H,
2 2 2 3
J(3,2) = J(5,6) = 6.6 (H-3, H-5); 8.91 d, 2 H, J(2,3) = J(6,5) = 6.6 (H-2, H-6); 12.60 s, 1 H (OH).
1
3
C
NMR (DMSO-d ): 14.6 s (CH ); 22.8 s (CH CH ); 24.5 s (CH CH CH ); 26.2 s
6 3 2 3 2 2 3
+
(
CH (CH ) CH ); 29.6 m ((CH ) ); 32.0 s (CH C=NOH); 48.0 s (CH -N ); 123.9 s (C-3, C-5);
2 2 2 3 2 11 2 3
1
6
46.3 s (C-2, C-6); 151.2 s (C-4); 154.7 s (C=NOH). For C23H41BrN O (441.5) calculated:
2.57% C, 9.36% H, 6.35% N; foun d: 63.21% C, 9.67% H, 6.11% N.
2
1
-Alkyl-4-[1-(h ydroxyim in o)eth yl]pyridin ium Brom ides 2. Gen eral Procedure
A solution of m eth yl pyridin -4-yl ketoxim e (0.073 m ol) an d alkyl brom ide (0.110 m ol) in
eth an ol (200 m l) was refluxed un til th e con version of oxim e was com plete (TLC: ch loro-
form –m eth an ol 5:1). After solven t evaporation , th e crude product was purified by colum n
ch rom atograph y (ch loroform –m eth an ol–aceton e–water 15:5:5:1) an d by crystallization from
a m ixture aceton e–dieth yl eth er. All th e prepared quatern ary oxim es were of un iform Z con -
1
13
figuration sin ce on ly on e set of sign als was foun d in th eir H or C NMR spectra.
-[1-(Hydroxyimino)ethyl]-1-octylpyridinium bromide (2a). Reaction tim e 37 h . Yield 65.4%.
4
1
M.p. 132–136 °C. H NMR (DMSO-d ): 0.81 t, 3 H, J(8′,7′) = 6.3 (CH ); 1.22 bs, 10 H ((CH ) );
6
3
2 5
+
+
1
2
(
.87 m , 2 H (CH CH N ); 2.22 s, 3 H (CH -C=N); 4.58 t, 2 H, J(1′,2′) = 7.4 (CH N ); 8.28 d,
2 2 3 2
H, J(3,2) = J(5,6) = 6.9 (H-3, H-5); 9.08 d, 2 H, J(2,3) = J(6,5) = 6.9 (H-2, H-6); 12.65 s, 1 H
1
3
OH). C NMR (DMSO-d ): 11.5 s (CH -C=NOH); 14.6 s (CH ); 22.7 s (CH CH ); 26.1 s
6 3 3 2 3
CH CH CH ); 29.1 d ((CH ) ); 31.4 s (CH CH CH N ); 31.8 s (CH CH N ); 60.6 s (CH N );
2 2 3 2 2 2 2 2 2 2 2
+
+
+
(
1
24.1 s (C-3, C-5); 145.3 s (C-2, C-6); 151.1 s (C-4); 152.1 s (C=NOH). For C15H25BrN O
2
(
329.3) calculated: 54.71% C, 7.65% H, 8.51% N; foun d: 54.67% C, 8.09% H, 8.78% N.
-Decyl-4-[1-(hydroxyimino)ethyl]pyridinium bromide (2b). Reaction tim e 40 h . Yield 69.8%.
1
1
M.p. 125.5–127 °C. H NMR (DMSO-d ): 0.82 t, 3 H, J(10′,9′) = 6.3 (CH ); 1.22 bs, 14 H
(
(
6
3
+
(CH ) ); 1.87 m , 2 H (CH CH N ); 2.22 s, 3 H (CH -C=N); 4.58 t, 2 H, J(1′,2′) = 7.3
2 7 2 2 3
CH N ); 8.28 d, 2 H, J(3,2) = J(5,6) = 6.6 (H-3, H-5); 9.07 d, 2 H, J(2,3) = J(6,5) = 6.6 (H-2,
+
2
1
3
H-6); 12.54 s, 1 H (OH). C NMR (DMSO-d ): 11.5 s (CH -C=NOH); 14.6 s (CH ); 22.8 s
6
3
3
(
CH CH ); 26.0
s
(CH CH CH ); 29.1
s
(CH (CH ) CH ); 29.4
t
((CH ) ); 31.4 s
2
3
2
2
3
2
2
2
3
2 3
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

1
656
Kivala, Cibulka, Hampl:
+
+
+
(
CH CH CH N ); 31.9 s (CH CH N ); 60.6 s (CH N ); 124.1 s (C-3, C-5); 145.3 s (C-2, C-6);
2
2
2
2
2
2
1
7
51.1 s (C-4); 152.1 s (C=NOH). For C17H29BrN O (357.3) calculated: 57.14% C, 8.18% H,
.84% N; foun d: 56.67% C, 7.56% H, 7.34% N.
2
1
-Dodecyl-4-[1-(hydroxyimino)ethyl]pyridinium bromide (2c). Reaction tim e 42 h . Yield
5
b
1
7
6
2
2.0%. M.p. 133–134.5 °C (ref. 128–131 °C). H NMR (DMSO-d ): 0.82 t, 3 H, J(12′,11′) =
.7 (CH ); 1.21 bs, 18 H ((CH ) ); 1.87 m , 2 H (CH CH N ); 2.22 s, 3 H (CH -C=N); 4.57 t,
H, J(1′,2′) = 7.3 (CH N ); 8.28 d, 2 H, J(3,2) = J(5,6) = 6.9 (H-3, H-5); 9.06 d, 2 H, J(2,3) =
J(6,5) = 6.9 (H-2, H-6); 12.66 s, 1 H (OH). C NMR (DMSO-d ): 11.5 s (CH -C=NOH); 14.6 s
6
+
3
2
9
2
2
3
+
2
1
3
6
3
(
3
CH ); 22.8 s (CH CH ); 26.1 s (CH CH CH ); 29.1 s (CH (CH ) CH ); 29.5 m ((CH ) );
3 2 3 2 2 3 2 2 2 3 2 5
1.4 s (CH CH CH N ); 32.0 s (CH CH N ); 60.6 s (CH N ); 124.1 s (C-3, C-5); 145.3 s (C-2,
2 2 2 2 2 2
+
+
+
C-6); 151.1 s (C-4); 152.1 s (C=NOH). For C19H33BrN O (385.4) calculated: 59.22% C, 8.63% H,
2
7
.27% N; foun d: 58.67% C, 8.61% H, 7.04% N.
-Hexadecyl-4-[1-(hydroxyimino)ethyl]pyridinium bromide (2d ). Reaction tim e 40 h . Yield
1
1
6
2
3.3%. M.p. 130–134 °C. H NMR (DMSO-d ): 0.82 t, 3 H, J(16′,15′) = 6.6 (CH ); 1.20 bs,
6 3
+
6 H ((CH ) ); 1.87 m , 2 H (CH CH N ); 2.22 s, 3 H (CH -C=N); 4.55 t, 2 H, J(1′,2′) = 7.3
2
13
2
2
3
+
(
CH N ); 8.28 d, 2 H, J(3,2) = J(5,6) = 6.9 (H-3, H-5); 9.03 d, 2 H, J(2,3) = J(6,5) = 6.9 (H-2,
2
1
3
H-6); 12.70 s, 1 H (OH). C NMR (DMSO-d ): 11.5 s (CH -C=NOH); 14.6 s (CH ); 22.8 s
6
3
3
(
(
CH CH ); 26.1
s
(CH CH CH ); 29.1
s
(CH (CH ) CH ); 29.6
m
((CH ) ); 31.4 s
2
3
2
2
3
2
2
2
3
2 9
+
+
+
CH CH CH N ); 32.0 s (CH CH N ); 60.7 s (CH N ); 124.1 s (C-3, C-5); 145.3 s (C-2, C-6);
2 2 2 2 2 2
1
6
51.1 s (C-4); 152.1 s (C=NOH). For C23H41BrN O (441.5) calculated: 62.57% C, 9.36% H,
2
.35% N; foun d: 61.88% C, 9.68% H, 6.34% N.
Kin etic Measurem en ts
Th e reaction s were perform ed un der pseudo-first-order con dition s (coxim e >> cPNPDPP) at 25 °C
an d pH 7.0 (0.1 M ph osph ate buffer) an d th eir course was m on itored with a Hewlett–Packard
HP8452 spectroph otom eter equipped with a th erm ostatted m ulticell tran sport cell h older
HP89075C at 400 n m (absorption m axim um of th e released 4-n itroph en oxide).
In th e case of th e reaction s perform ed in m icellar solution s, th e reaction m ixtures were
–
3
prepared in 1-cm spectroph otom etric cells by m ixin g appropriate volum es of 5.0 × 10
M
buffered solution of ketoxim e 1 or 2, 2.0 × 10– M solution of a m icelle-form in g surfactan t,
2
buffer, an d redistilled water. Th e resultin g con cen tration of th e surfactan ts (CTAB, Triton
–
2
–1
–3
X-100, Brij 35) was 1.0 × 10 m ol l . Th e reaction s were in itiated by in jection of 2.0 × 10
M
PNPDPP solution in aceton itrile (20 µl) in to th e spectroph otom etric cell con tain in g 1980 µl
–
5
of th e buffered m icellar solution , th e resultin g con cen tration of th e substrate bein g 2.0 × 10
–
1
m ol l
.
Th e reaction s in o/w m icroem ulsion were perform ed an alogously. Th e reaction m ixtures
(
1980 µl) were prepared by m ixin g appropriate volum es of 5.0 × 10–2 M solution of ketoxim e
1
or 2 in m icroem ulsion an d n eat m icroem ulsion . Th e reaction s were in itiated by in jection
–
3
of 2.0 × 10 M PNPDPP solution in aceton itrile (20 µl) in to th e spectroph otom etric cell.
No ch an ges in pH were observed durin g kin etic run s. Th e reaction s followed a first-order
kin etics at least up to 95% con version . Th e pseudo-first-order rate con stan ts kobs were ob-
tain ed by n on -lin ear regression an alysis of th e absorban ce vs tim e data usin g th e equation
At = (Ain f – A ) [1 – exp (–kt)] + A . Regression an alysis was perform ed usin g program m e
0
0
1
8
Origin 6.1 (ref. ). In all cases, th e correlation coefficien t r > 0.999. Th e kin etic run s were
perform ed in duplicate; th e differen ce in th e rate con stan ts did n ot exceed 5%.
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1642–1658

Cleavage of 4-Nitrophenyl Diphenyl Phosphate
1657
As publish ed elsewh ere5,19, it is th e deproton ated h ydroxyim in o group in pyridin ium
oxim es wh ich is th e n ucleoph ile attackin g th e ester fun ction . Th erefore, th e apparen t
secon d-order rate con stan ts k2 were obtain ed as slopes of th e pseudo-first-order rate con stan t
kobs of th e PNPDPP cleavage vs oxim ate an ion con cen tration plots; th e oxim ate an ion con -
cen tration s coxim ate at pH 7.0 were calculated from an alytical con cen tration s c
an d th e
oxim e
+
correspon din g pKa values usin g th e equation coxim ate = coxim e K /(K + [H ]).
a
a
The authors thank Prof. K. Holmberg, Chalmers University of Technology Göteborg, for the
know-how concerning the preparation and treatment of microemulsions and for helpful discussion.
This study was supported by Czech Science Foundation, grant No. 203/04/0488.
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